LIVING AMONG the OAKS a Management Guide for Woodland Owners and Managers

University of California Agriculture and Natural Resources http://anrcatalog.ucdavis.edu | Publication 21538 LIVING AMONG THE OAKS A Management Guide for Woodland Owners and Managers

Author: DOUGLAS D. McCREARY, Natural Resources Specialist, UC Cooperative Extension Technical Editors: WILLIAM D. TIETJE, Natural Resources Specialist, UC Cooperative Extension; SABRINA L. DRILL, Natural Resources Advisor, UC Cooperative Extension; GREGORY A. GIUSTI, Forests and Wildland Ecology Advisor, UC Cooperative Extension; LAURENCE R. COSTELLO, Environmental Horticulture Advisor, Emeritus, UC Cooperative Extension

University of California Oak Woodland Conservation Workgroup

What is more characteristic of the oak woodlands a landscape of Cali- All Californians can assist in the California landscape than the oak? fornia that symbolizes values we hold protection and enhancement of native Round-crowned oaks dapple the dear—strength, beauty, adaptability, oak resources, but nobody is in a better rolling hills, solitary monarchs shade and longevity. position to do so than the owners and our rural roads, and valley giants But intensifying land use in oak managers of oak woodlands. Those stretch skyward in banners of leaves woodlands has brought problems who own homes or property in the oak and lichen. Both past and present-day along with it: soil erosion, reduced landscape can help shape the future travelers have stopped in awe of our forage production, poor regeneration by their decisions, which collectively native oaks, and countless photo- for some oak species, and degraded direct the management and land use of graphs and memories are framed wildlife habitats. Oak woodlands today more than 7 million acres (2.8 million by their spreading, weather-worn are clearly showing the effects of the hectares) of the state. This publication branches. The oak is particularly last 200 years of human habitation. is designed primarily for the owners emblematic of the inland regions of home lots or small acreages, but of California, where scattered oaks, owners and managers of larger proper- rolling pastures, and distant cattle are Oaks provide ties can also apply much of the infor- common elements of an infinitely • shade and shelter mation, especially to areas where native variable and ever-changing landscape. • wildlife and fisheries oaks grow around the ranch home. It In this region—often called the habitat brings together helpful information hardwood range or oak woodlands • soil protection (erosion about living—and making a living— by land managers—the vistas of control) among the oaks. The University of oaks, pasture, and livestock bestow California Oak Woodland Conserva- • increased property values a tranquility that sometimes belies tion Workgroup hopes that you will beautiful landscapes the fourth element: people. Like the • find this information useful as you earliest Californians, people today • food and fuel manage your land and make decisions come to the oak woodlands for food, • recreational opportunities that shape the future of California’s shelter, and beauty. Many consider oaks and oak woodlands. 2 ANR Publication 21538 Living among the Oaks

aks of the ardwood ange OCalifornia has 21 native species H of oak in the genus Quercus, R 10 of which grow to tree size. Of these, 8 are conspicuous members of the oak woodland plant community. All are relatively slow growing and long lived.

Valley oak (Q. lobata) Engelmann oak (Q. engelmannii) This tall, spreading, winter-deciduous This semideciduous oak has a oak was once an important member narrow distribution, primarily of the Central Valley’s riparian in western San Diego County, forests, but agricultural conver- where it replaces blue oak as sions and development have greatly the dominant species. It has reduced the acreage it occupies. been severely impacted by agri- From Shasta County to Los Angeles cultural conversions and, along County, it is still a conspicuous oak with blue oak and valley oak, is

in the landscape, especially in valley BaileyHart Gordon not regenerating well. bottoms and on deep alluvial soil. It

Alice B. Addicott Alice B. is the largest oak in California. California black oak (Q. kelloggii) Blue oak (Q. douglasii) This species is a member of the black This deciduous oak is the oak subgenera and loses its leaves in dominant oak in the wood- winter. It most commonly grows in lands from Shasta County mountainous areas, and in the Sierra to Kern County, growing in Nevada it is an important component the foothills of the Sierra of the mixed-conifer forests. It typi- Nevada, Coast, and Trans- cally receives more than 25 inches verse mountain ranges. It (64 cm) of annual precipitation and often grows in association produces a strong reddish-brown wood with interior live oak (Q. that is compared to northern red oak wislizeni) and foothill pine (Q. rubra). Its acorns were considered (Pinus sabiniana) and toler- the best tasting by many tribes of

ates relatively harsh sites. BaileyHart Gordon Native Americans throughout the state. In addition to dropping its leaves in winter, it exhibits drought deciduousness—that is, the capacity to shed foliage earlier than Oregon white oak (Q. garryana) normal in response to drought. This deciduous white oak is common in northern California and extends Coast live oak (Q. agrifolia) far north, all the way to Vancouver This evergreen oak occurs from Island in British Columbia. It prefers southern Mendocino County a moderate climate with warm southward into northern Baja summers and freezing winters and California, primarily in the Coast between 20 and 50 inches (51 and Range. On favorable sites it 128 cm) of precipitation. In Califor- often attains a rounded, spread- nia it grows in a variety of habitats ing appearance. It is a member and is often associated with bay of the black oak subgenera and laurel (Umbellularia californica), is one of four California oak Douglas fir (Pseudotsuga menziesii), species that is susceptible to black oak, Pacific madrone (Arbutus

Hart Gordon BaileyHart Gordon Sudden Oak Death. menziesii), and tanoak (Lithocarpus densiflorus). Interior live oak (Q. wislizeni) Canyon live oak (Q. chrysolepis) This evergreen oak is widely This evergreen species has a broad This evergreen oak is widely distribution, extending from Oregon distributed in California from to Baja California, and it can grow Siskiyou County south to Baja from sea level to high in the moun- California. It is abundant in the tains. The wood is very strong and Sierra Nevada foothills, and close grained and was originally in the Coast Range it occupies used for tools and implement higher, drier, and more inland handles; hence one of its common sites than does coast live oak. names is maul oak. Another common It is generally found in more name is gold cup oak, because it has fine yellow powder covering the heavily wooded sites than blue Geri Hulse Stephens oak, and in chaparral habitats acorn cup, or cap. or other dry locations it often develops a shrubby form. Courtesy of the UC Davis Arboretum Source: McMinn, Maino, and Shepherd 1935. Living among the Oaks ANR Publication 21538 3

Needs and Conflicts these elements can present formidable Threats to the Root Zone In designing and building homes, obstacles to the health and survival of The following human activities are gardens, orchards, and places for oak trees. However, harmful effects can the ones that most commonly alter animals, your decisions are shaped by be minimized by thoughtful manage- a tree’s root environment, potentially your overall objectives for your land. ment practices. And how we manage damaging or killing it. Whether your land is a residential oak woodlands will likely become even site, used for grazing, or maintained more critical under the stresses associ- as natural open space, you will need ated with climate change. to consider various management Building around Oaks: options. As you choose management Protecting the Root Zone approaches for your land, also take The most vulnerable part of a mature CONSTRUCTION into account your oak trees and oak tree is the root system and, in evaluate whether or not your planned particular, the root crown at the DANGER: activities are compatible with oak base of the trunk. Although most Proceed with conservation and the basic needs oaks do have a deep taproot, many CAUTION of the trees. Remember that well- oak roots are relatively shallow and managed oak woodlands can also help extend outward from the root crown, enhance other natural resources, such reaching some distance beyond the as soil and water. Careful planning tree’s drip line (the outermost edge and design can often provide benefits of a tree’s foliage). For management Changes in grade. This includes for both people and oaks. purposes, think of a tree’s root zone any changes in the ground level under Past development among the oaks as extending out at least one-third the tree, either by mounding up soil has revealed specific areas of conflict. farther than the distance to the drip or removing it. Excavating soil can Often impacts to oaks have not been line. Ideally there should be no distur- directly cut and destroy roots and adequately addressed in planning bance within this zone. This means expose them to damage from surface documents and mitigation require- no grading, digging, trenching, using activities. Mounding up soil can ments. But a 2004 California state law of fill soils, covering the ground with reduce oxygen to the roots. Depending (Public Resources Code § 21083.4) asphalt or concrete, or landscaping on climate and soil moisture, addi- requires mitigation if projects in oak with plants that require more than tions of soil can also encourage root woodlands have significant impacts on two or three summer waterings. Also, rots. Use retaining walls outside of the the environment. It has also become excessive foot traffic, operating heavy drip line to protect the natural grade apparent that, in addition to the equipment, and parking vehicles under the tree. If there is no alterna- removal of trees, certain construc- (particularly heavy ones) should be tive to adding soil within the drip line, tion practices can seriously injure or avoided in this zone to avoid compac- consult a qualified arborist specializing kill oaks. Construction activities can tion. It is preferable to retain natural in oaks for strategies to minimize increase (or decrease) fire hazards, litter (fallen leaves, twigs, and bark) or injury. Also, review the publications creating liability and management add mulch to cover the soil surface. If listed in the “References” section. problems. Gardening practices such modifications are unavoidable, strive Changes in drainage. Irrigation as amending the soil, planting lawns, to keep this area in as natural a condi- and changes in the drainage around or irrigating under established oaks tion as possible, and keep ground an oak can result in water in the root can damage them. Domestic animals, disturbance as far away from a tree’s zone during the summer when soil as well as insect and disease pests, trunk as possible. temperatures are high and soils are also can take a toll. In combination, normally dry. This can promote the 4 ANR Publication 21538 Living among the Oaks

proliferation of harmful soil microor- that should always be left undisturbed local soil moisture, and watch for ganisms that injure roots. Saturated and preferably covered with mulch. bank or hillside cuts that could alter soils can also inhibit oxygen move- Trenching. Trenching is a drainage patterns. ment into the root zone. These factors leading cause of tree mortality. When Fire in California’s can ultimately result in tree death. utility trenches are dug into the root Oak Woodlands zone, major portions of a tree’s root system may be cut or damaged. When Californians are keenly aware that several large roots are damaged, tree fires regularly occur in our state and death may follow. Trenching in the can have devastating consequences. FUNGUS root zone should be avoided when- Recently there have been some cata- ever possible. If trenching cannot strophic fires in oak woodlands. The DANGER: be avoided, identify the location severity of these fires was partially due Don’t Water of lateral roots using a pneumatic to fire suppression activities during the last 100 years that have increased Mature Trees trenching tool. Probably the best alternative to trenching is to place fuel loads and made it more difficult utilities in a conduit that is bored to suppress or contain woodland through the soil. If utility conduits fires that do start, especially during are unavailable, try to have all utilities extreme fire weather. Also, more placed in a single trench, as multiple people are now living within these Soil compaction. Heavy foot trenching causes greater damage. fire-prone ecosystems, which compli- traffic or the operation of heavy cates fire-fighting activities. One equipment can cause soil compac- consequence of the recent spate of tion, especially when the soil is fires was the revision of the California wet. Compaction causes the spaces state law that requires fuel reductions between soil particles to become ROOTS around homes and the removal of compressed, reducing gas exchange. AT RISK: vegetation that could help fires spread Since gas exchange is needed for Avoid Trenching, (Public Resources Code § 4291). root function, compaction can cause Increasing clearances and removing significant injury to oaks. When the Compaction, and Grade “ladder fuels” can greatly reduce the ground is covered with nonporous Changes in the risk that homes in the paths of fires materials such as asphalt or concrete, Root Zone will be lost. the free passage of moisture, air, and Once the fires have passed and the other gases within the root zone is embers have cooled, property owners impeded. In addition, soil compac- want to know if their oaks have been tion can occur in preparation for and killed. Often they haven’t been. Even during paving. As an alternative to Disturbance beyond the root zone. if all of the leaves on an oak tree have common paving materials (asphalt Beyond the root zone mature oaks are been scorched and the tree looks and concrete), there are porous usually less affected by landform and dead, new leaves will often emerge materials that are more compatible drainage changes, soil compaction, and start to grow the following with the oak environment and make paving, and trenching activities. But spring—or even sooner—and the tree excellent ground coverings. Regard- indirect effects must still be considered. may suffer little long-term damage. less of the permeability of the ground Avoid fill materials that could alter flow It is therefore important to wait until covering, nothing should be placed patterns, resulting in water collecting the following year to determine if within a 6-foot (1.8 m) radius of a around trees. Consider the effects of trees have been killed from fire. And tree’s trunk. This is the minimum area nearby ponds or swimming pools on even if the aboveground trunk has Living among the Oaks ANR Publication 21538 5

ative lants ompatible with aks NBelow is a selection Pof California native plantsC that require little water and can therefore O be used in landscaping under and around oak trees. Once established—usually after a year—they require little care, minimal water, and offer beautiful foliage. Sometimes they have showy blossoms with pleasant fragrances as well. When planting near oaks, avoid injury to roots while digging planting holes, and stay outside the drip line if possible. Also add mulch after planting to help conserve soil moisture. Shrubs (partial shade) Shrubs (full sun) Deciduous or annual Carpenteria californica, carpenteria Fremontodendron californicum, herbaceous plants Ceanothus spp., wild lilacs: F. mexicanum and cultivars, Clarkia spp., clarkias C. griseus, C. thysriflorus, Fremontia, flannel bush, Collinsia spp., Chinese houses C. maritimus, plus cultivars: California Glory, Pacific Sunset Dodecatheon clevelandii, shooting stars C. Joyce Coulter, C. Ray Hartman. Galvezia speciosa, island snapdragon Eschscholzia spp., poppies Cercis occidentalis, western redbud Lupinus albifrons, silver bush lupine Montia perfoliata, miners lettuce Cercocarpus betuloides, Lupinus chamissonis, Chamisso bush Nemophila menziesii, baby blue eyes mountain-mahogany lupine Oenothera spp., evening primroses Eriogonum arborescens, Santa Cruz Mimulus aurantiacus, bush monkey Sisyrinchium bellum, blue-eyed grass Island wild buckwheat flower Viola pedunculata, yellow pansy Garrya elliptica, silk-tassel bush Mimulus puniceus, red monkey flower Zauschneria californica, California wild Heteromeles arbutifolia, toyon Penstemon clevelandii, Cleveland’s fuchsia Mahonia spp., barberries and mahonias: penstemon, and other species Bulbs M. dictyota, M. fremontii, Romneya coulteri, matilija poppy M. haematocarpa, M. pinnata Ground covers Brodiaea species and related genera: Prunus ilicifolia, holly-leaf cherry Dichelostemma pulchellum Rhamnus californica, coffeeberry Baccharis pilularis ssp. pilularis, Triteleia laxa Ribes spp., gooseberries: dwarf coyote bush Calochortus spp., Mariposa lilies R. aureum var. gracillimum, Ceanothus griseus var. horizontalis, Chlorogalum pomeridianum, soap plant R. malvaceum, Carmel creeper Lilium pardalinum, leopard lily R. speciosum, R. sanguinium, Ceanothus maritimus, Hoover ceanothus Trillium chloropetalum, common trillium R. viburnifolium Ribes viburnifolium, Catalina currant Rosa californica, California wild rose Evergreen herbaceous plants For more information about these and Rosa californica, Plena, double Dryopteris arguta, wood fern other California native plants compatible California rose Eriogonum umbellatum var. polyanthum, with oak gardens, including which species Salvia clevelandii, San Diego wild sage buckwheat are native to your part of California, Salvia leucophylla, coastal white sage Heuchera maxima, giant alum root contact local arboreta, botanical gardens, Iris douglasiana and hybrids and the California Native Plant Society Viguiera deltoidea var. parishii (see “Online Resources”).

Fungus danger zone! Keep dry and well drained.

Canopy

Retaining wall

Fill Drip line

` Retaining wall 6 Drip line Root crown

New grade

Root zone

It is essential to limit activities in the root zone that could damage the tree’s roots. courtesyConcept of Sacramento County Office of Education 6 ANR Publication 21538 Living among the Oaks

been so severely damaged that the by the time symptoms appear, the tree later infect other trees—even after tree dies and has to be cut down, is declining and remedies may be too the death and removal of the host oaks will generally sprout from their late. A qualified arborist should be plant. Fruit trees and landscape plants stump. These sprouts can eventu- called when the following symptoms nearby, particularly those that are irri- ally grow into a new tree, and much are noticed: gated during the summer, may also be more quickly than when planted as • Loss of tree vigor, twig dieback subject to infections. acorns. While fires are generally not and wilting, abnormally yellowish good for trees, oaks have evolved in an leaves, and wounds on the bark environment where regular fires have that ooze rust-colored fluid. These always occurred. As a result, they are symptoms are indicators of crown well adapted to survive this natural rot (Phytophthora spp.). phenomenon. • Foliage turning brown, and the oozing of a dark brown, viscous fluid from the trunk. These symptoms are often accompanied by the presence of bark beetles Doug McCreary and fruiting bodies of Hypoxylon Heart rot is common in mature oaks. fungus on the trunk of the tree. These are symptoms ofPhytophthora ramorum, the agent responsible for Sudden Oak Death (see below). • Another fungal malady, called Dieback of branches, emergence heart rot, occurs when one of several of honey-colored mushrooms at wood decay fungi degrades the heart- or near the base of the tree in the wood of an oak. Although this does early winter, often accompanied by not usually impair the tree’s vigor, it a white fan-shaped fungus growth does weaken it structurally. Weakened between the bark and sapwood, branches can break off and a weak- and black shoestringlike structures ened trunk may not be able to support in the soil. These are indicators of Bill Tietje the crown, especially during a wind- Fire in California’s oak woodlands is an a serious disease called oak root storm. Heart rot commonly develops ongoing threat. fungus, Armillaria mellea. in large pruning wounds. Regular Armillaria is often present on examination of the tree and judicious Oak Pests the roots of wildland oaks, even pruning and bracing can prolong the when there are no obvious outward life of an oak with heart rot. Oaks in natural settings are relatively symptoms. Under natural conditions Mistletoes resistant to severe damage from this disease is rather benign, and it pests, especially native pests that is held in check by summer drought. These parasitic plants grow in the have co-evolved with oaks (but see However, Armillaria thrives in warm, branches of many oaks and can cause the section on Sudden Oak Death, moist conditions—a situation that is structural weaknesses that make the below). However, when compromised created when the area under a tree is tree more vulnerable to branch break- by soil compaction, changes in soil watered during the summer. Once the age. Small infestations may affect the moisture, or other disturbances, trees roots of a tree are seriously infected, appearance of a tree but generally can have difficulty fending off organ- the fungus can persist in soil organic have little impact on tree health or isms that cause injury. In some cases, material for many years and can vigor. Even large infestations, which adornment to theiroaktrees. mossanattractive consider Spanish branches.infested Many people bereduceding andcan by pruning but thesituationthreaten isnotlife - moss, ladentree withSpanish heavily reduced duetoshading ofleaves in a to oaks. Tree growth may beslightly threat soisnotaserious not parasitic nor alichen, butabromeliad.) Itis statesisneither amoss in thesouthern lichen.Spanish mossthatgrows (The mossbuta notatrue isactually fornia Spanish mossthatgrowsThe inCali- Spanish moss totheground.fallen eatmistletoefoliagethathas will deer, for andeven the berries which ofbird speciesthateat avariety for mistletoes are native andbeneficial herbicides. Itshouldbenotedthat orusingregistered branches infected ofways,ety removing the including becontrolled- Mistletoes can inavari weaken trees,can them. kill rarely Coast liveoaksladenwithSpanishmoss. Jack Kelly Clark. Living amongtheOaks

Chinese hats. resemblecan seaurchins, sponges, or multicolored shapeson oakleaves that ornaments, exotic whileothersform lookgalls likedanglingChristmas begintofeed.larvae ofthese Some waspslay gall theireggsandthe small released when response toenzymes example, are swellings in harmless ous andhealthy. Mostoakgalls, for ifthetree isvigorimpact—especially - trees, withoutmuch adverse usually branches, trunk, androots ofoak insectsliveInnumerable on theleaves, Insect pests common ontwigs, branches,andleaves. Colorful gallscausedbygallwasps are

Jack Kelly Clark, courtesy of Laurence R. Costello UC Statewide IPM Program oaks inSanDiegoCounty. The goldenspottedoakboreriskilling tions ofground squirrels orother been cases, however, where popula - damage mature trees. There have seedlings, seriously do they butrarely regeneration on by small chewing animalsmaygrazing inhibit natural threat tomature oaks. Browsing or In mostcases, mammalsposelittle Mammal pests Diego County.live oaksin San spreadingactively coast andkilling coxalis), is which oak borer (Agrilus or Mexico, isthegolden spotted have from arrived recently Arizona insectpest,new however, to believed damaged by orkilled them. Aserious aretogether andrarely trees seriously associated native insectshave evolved treatment.is toolatefor Oaksandthe becometime thesymptoms evident, it treat oakinsects, by the butoften insecticidesareSome registered to reducedof greatly photosynthesis. defoliationisminimalbecause during long-term damage, althoughgrowth recover year thefollowing withlittle are defoliated, completely usually they outbreaks. However, whentrees even severe during effects have striking on anumberofoakspecies andcan eating insectsare relatively common branches), oakmoths, and otherleaf- on thebark andsmall scales oftwigs aspinhead-size (appearing scales injury, however. For instance, pit Some insect pests do cause insectpestsdocause Some AN R Publication 21538

Tom W. Coleman, courtesy of USDA Forest Service 8 ANR Publication 21538 Living among the Oaks

MANAGING AND ENHANCING OAK RESOURCES Livestock grazing has been the dominant land use throughout a majority of the oak woodlands since European settlement, and this use has contributed to the open, pastoral character of much of California’s countryside. But it is also in portions of this region that the regeneration for several oak species has been poor, especially during the last 100 years. Cattle are the oft-named culprits since they consume acorns and seedlings Pavel Svihra Pavel and browse saplings and mature trees. Sudden Oak Death continues to kill oaks in 14 coastal counties. They can also compact rangeland soils and remove organic matter. Compac- tion makes it harder for young roots to ground-dwelling rodents have caused California’s 21 species of native grow downward, and removing organic damage to oak roots or girdled young oaks are susceptible to this disease: matter can diminish soil fertility. stems. Take measures to control these coast live oak, California black oak, However, there are situations populations if oak vigor is diminished Shreve’s oak (Q. parvula var. shrevei), where oak regeneration remains poor or if there is extensive excavation and canyon live oak. Currently it even when livestock are absent. Obvi- by animals in the root zone. The does not appear that members of the ously the oak regeneration problem aboveground part of seedlings or white oak subgenus, including blue is more complex, and factors other saplings can be protected by fencing, and valley oaks, are susceptible. As of than livestock are also involved. These wire cages, or treeshelters (see below). 2009, SOD had been confirmed in may include the replacement of native The roots of seedlings planted in such 14 coastal counties, extending from perennial bunchgrasses by introduced areas can be protected belowground Monterey to Humboldt, with locally Mediterranean annuals; greater hare, by covering the root ball at the time devastating effects. Fortunately, deer, gopher, and ground squirrel popu- of planting with a wire cage. it appears that conditions further lations; insect and soil fauna changes; inland (e.g., the Central Valley and Sudden Oak Death and alterations in the populations of the Sierra Nevada foothills) are too acorn- and seedling-eating animals. Sudden Oak Death (SOD) is a hot and dry to permit its spread Whatever the causes, it appears that relatively new disease that affects there. There is an extensive research, management intervention is now several native California oak species. monitoring, and education program— needed—of both land and oaks— It is caused by Phytophthora ramorum, coordinated by the California Oak if oak trees are to continue their tradi- a funguslike water mold that causes Mortality Task Force—to curtail the tional and ecological role as a keystone bark cankers which can girdle and spread of this disease and minimize species on the hardwood range. kill mature trees. To date, four of its impact. Living among the Oaks ANR Publication 21538 9

Oak Health Check Check for tree growth • Tree size is not a good indicator of health. Oaks growing on steep, dry sites may be smaller than others nearby but may still be very healthy.

• Twig growth for the season can vary greatly. If twig growth is less each year, however, the tree may be declining.

• Look for bark growth cracks on a tree’s trunk. Cracks appear as widening fissures on existing bark. Tissue in the cracks should be bright green or pink when scratched. Loose bark indicates dead tissue.

Check for pests and stress • Watch for disease or insect infestations indicated by leaf loss, changes in leaf color, twig dieback, sooty foliage, wet sticky foliage, or other significant changes in appearance.

• Watch for twig and branch dieback. This can be an indication of disease, root loss, or other root-zone problems.

• Watch for emergence of clumps of honey-colored mushrooms at or near the base of a tree in the fall and early winter. These are often accompanied by a white, fan-shaped fungal growth between the bark and sapwood. These symptoms accompany oak root fungus, Armillaria mellea.

• Early leaf loss may signal declining vigor—but not always. Deciduous oaks have been noted as being drought deciduous. This occurs during dry years when soil moisture is depleted early and oaks shed their leaves early to help conserve moisture. Deciduous oaks normally do not lose their leaves until late November—but under very dry conditions, they can shed leaves in midsummer. Early leaf loss appears to cause little long-term damage.

Check for structural weakness • Oaks growing in a natural setting usually do not require pruning. However if dead or dying branches pose a safety hazard or threaten buildings, have them pruned or cabled by a qualified arborist.

• Watch for developing structural weaknesses caused by wood decay, mistletoe, heavy foliage, or poor branch structure. Co-dominant stems, branch attachments with included bark, long horizontal limbs, extensive decay in branches, and cracks developing in crotches are all indications of weak structure. Consult a qualified arborist to determine if pruning will improve structural stability.

• Avoid damage to structural roots.

Check for poor drainage • Standing water should not be present within a tree’s root zone.

• Building, landscaping, or other activities near oaks should not alter drainage patterns in a way that increases water in the root zone.

• Avoid compaction in the root zone.

Check the root crown condition by digging carefully at the base of the tree • A characteristic root flare at the base of the tree should be obvious. If not, the trunk has been buried and the soil should be excavated to the original grade.

• Large decay pockets at the root crown may indicate a dangerous condition, and a qualified arborist should evaluate the tree for structural integrity. 10 ANR Publication 21538 Living among the Oaks

In managing land, animals, trees or seedlings can help alleviate not regenerating well in certain areas plants, and other resources, there problems. If damage is severe, you may of the state. In addition to poor natu- are many things landowners can do want to consult a qualified arborist for ral regeneration, the total acreage of to encourage healthy, vigorous oak remedial treatments. these species has been depleted from populations. Some basic manage- residential and commercial develop- Pasture management ment considerations are discussed in ment, range improvement, agricultural the following section. But, in making In managing your pastures, always conversions, and firewood harvesting. management decisions that affect remember the general recommenda- To ensure that these species remain your oaks, your greatest guidance tion against summer watering of oaks. important components of the natural may come from your own observa- If your pastures are irrigated in the landscape of California, it may be tions and experiences. Oaks, and summer, adjust irrigation systems to necessary to encourage natural regen- the ecological settings where they apply water outside of the root zone eration or to actively restore oaks by grow, vary tremendously from place only. Adjusting watering schedules planting acorns or seedlings. During to place, meaning that no one type to infrequent but long periods of the last 20 years, much has been of management is appropriate for all irrigation will also reduce stress on learned about what works and what situations. So, before making deci- oaks. Always try to keep the base of does not. Based on research and field sions, study what is actually taking the tree dry. Observe the location trials, we now feel we can successfully place on your land and experiment of watering devices and other water regenerate native oaks, although it is with what you do. You may discover sources to make sure that the area often necessary to carefully plant and techniques that could also be useful to beneath an oak’s canopy does not maintain them. Below are general other landowners. become wet from leaky water lines, guidelines for encouraging natural valves, holding tanks, or from animals Oaks and Grazing Animals regeneration; collecting, storing, and splashing in troughs. planting acorns; growing seedlings Grazing and browsing animals are Promoting Oak Regeneration in containers; and outplanting acorns ubiquitous components of oak wood- and seedlings in the field. Additional lands, but they can damage mature As noted previously, there is evidence information is available in Regenerat- trees as well as seedlings. Watch that several species of native oaks in ing Rangeland Oaks in California, your trees for signs of damage and California—particularly blue oak, UC ANR Publication 21601 (see take care that the number of animals valley oak, and Engelmann oak—are “References”). congregating under them does not cause excessive soil compaction, expose the root crown at the base of the trunk, or expose surface roots. Also watch for excessive chewing on tree trunks. Horses and goats can kill trees by chewing off the bark around the entire circumference of the tree, thereby girdling it. These types of problems are more likely in pastures where animals are concentrated. Measures such as reducing numbers of animals, alternating pastures in use, and installing exclosures, screens, UC Cooperative Extension UC Cooperative treeshelters, or other protective devices Acorn production among California oaks is highly variable from tree to tree and from to keep animals away from sensitive year to year. Living among the Oaks ANR Publication 21538 11

Encouraging natural oak regeneration Acorn collection, storage, and planting rapidly lose viability if they dry out, Areas particularly favorable to natural Acorns are the seeds of oak trees. They so it is important to place them in regeneration include north-facing begin to develop on the tree in spring, plastic bags in cold storage soon after slopes, regions with average annual following pollination and fertiliza- they are collected. They can be stored precipitation greater than 20 inches tion, at about the same time the new for several months, but members of (50 cm), deep or alluvial soils, swales, leaves are starting to form. Oaks are the white oak subgenera, including or other places with subsurface water. wind pollinated, so environmental both blue and valley oak, will germi- Because seedling mortality is usually conditions at the time of flowering nate in cold storage and begin to high, regeneration possibilities are can affect the size of the acorn crop. grow a radicle, or new root. Acorns best in areas that can remain free Warm, dry, and windy conditions do not store well, and it is therefore from grazing animals for several allow the pollen from male flowers, important to plant them as soon as years and where existing mature trees or catkins, to find receptive female the soil becomes sufficiently moist provide acorns. Sites offering some flowers, resulting in larger acorn crops. after the first rains in the fall. They natural protection, such as rocky or Acorns ripen in the fall, usually in should be placed on their sides and shrubby areas, or steep slopes that October and November. The acorns of planted between 0.5 and 1.0 inch naturally exclude or impede the some oak species ripen in a single year, (10 and 25 mm) deep. The chances movements of deer and livestock, may while it takes 2 years for other species. of vigorous initial growth can be also be favorable. In some areas small When they mature in the fall, they improved by excavating a hole several seedlings are abundant but larger begin to change color from green to inches wide and up to 1.5 feet (50 saplings are rare or nonexistent. This yellow to brown, and the attachment cm) deep prior to sowing (and filling often occurs because both domestic to the acorn cup, or cap, loosens to the hole back up with soil), which and wild animals repeatedly browse eventually allow them to fall to the allows the initial root to more easily small seedlings, killing them or keep- ground. However, one can pick acorns grow downward. Direct planting of ing them stunted. To enhance growth, directly from tree branches before they acorns eliminates the root distur- seedlings can be protected from fall to the ground and are consumed bance that occurs with transplanting damaging animals by creating fenced by birds, squirrels, or deer, or dry out seedlings and allows more natural areas, called exclosures, that protect and decline in quality. Acorns are ripe root development. seedlings from animals. Treeshelters when they can easily be dislodged (see description below) can be used from the cup by gentle twisting. When to protect single seedlings, or larger the acorns are ripe, they can also be exclosures can protect entire groves. collected by hitting tree branches with In pastures grazed by cattle, research long poles to dislodge them, then has shown that the season of grazing collecting them from the ground. can influence damage levels. Damage Once collected, all of the acorn is usually greatest in the summer and cups should be removed before early fall when few other green plants placing the acorns in a container of are available. Grazing only during water. This float test helps separate the green season, when other forage healthy acorns from damaged or is abundant, can lessen damage and immature ones. Floaters are much encourage greater seedling growth. less likely to be viable and should Strategically placing water and feed be discarded. Sinkers are surface supplements away from potential oak dried and then put in plastic bags regeneration areas can also reduce and placed in a refrigerator or cold Doug McCreary damaging impacts to oaks. storage unit maintained between Acorns can be collected from the 32° and 40°F (0° and 4.4°C). Acorns branches of oak trees. 12 ANR Publication 21538 Living among the Oaks

Growing oak seedlings in containers An alternative to directly sowing acorns is to grow oak seedlings in containers and then plant them in the field. These seedlings often have higher survivorship than directly planted acorns, but they also cost far more. It appears that overplanting with acorns is often more cost effective per surviving seedling than planting container stock. When planting on a small scale, however, it may make little difference. There are a variety of container types and sizes that can be used, but

because oaks rapidly grow a deep Jack Kelly Clark taproot, it is preferable to use tall, In a study at the Sierra Foothill Research and Extension Center, treeshelters were narrow containers instead of short, shown to help oaks become established. wide ones. It is also important to prevent seedlings from growing so spraying herbicides, or mulching can vegetation is removed, there still may much that their roots fully occupy the make the difference between survival be significant obstacles to overcome available soil space in the container, and death for young oak seedlings. since a variety of animals seem intent causing the seedlings to become pot- It can also enhance growth rates. on eating them. Oaks are vulnerable bound. Before this occurs they should Research suggests that maintaining to herbivory from a range of animals, either be transplanted to a larger pot a weed-free circle, with a 2-foot from small insects and slugs, to hares or planted in the field. Generally, (60 cm) or larger radius, around seed- and rodents, to deer and cattle. One oak seedlings should not be grown lings for the first couple of years after device that has proven particularly in containers of one gallon (3.8 liter) planting increases soil moisture and effective in protecting seedlings or less for more than a year. It is also promotes better survival and growth from a wide range of animals is a critical to plant seedlings in the field (McCreary 2001). Augering holes treeshelter. This is a double-walled, early in the season—generally by the prior to planting can also improve plastic tube that is placed over indi- end of January—so that they can seedling field performance on certain vidual seedlings. It not only excludes begin to grow roots before the soil sites by allowing seedling roots to a variety of animals, but it also stimu- starts to dry out. more easily penetrate downward lates seedling growth by acting as a Seedling planting and protection where they can obtain soil moisture mini-greenhouse. Most oak woodlands in California unavailable at shallower rooting If acorns or seedlings are planted have an understory of dense, non- depths. Fertilizing seedlings with after heavy rains when soils are moist, native annual vegetation. These plants slow-release fertilizer tablets at the watering is not needed. Otherwise, it compete with oak seedlings for mois- time of planting has also resulted in is a good idea to water planting sites ture and nutrients and can severely significant increases in both diameter thoroughly at the time of planting. limit their growth and survival. It is and height growth on certain sites. Periodic watering during the first 2 therefore important that these plants However, even if healthy seed- or 3 years usually improves survival be controlled. Eliminating weeds near lings are planted correctly at the and growth, but it may not be logis- planted oaks by scalping (i.e., hoeing), right time of year and competing tically feasible for remote planting Living among the Oaks ANR Publication 21538 13

sites. In these instances it is even to browsing pressures and thus helps balances. For instance, blue jays are more essential to eliminate competing ensure the success of regeneration important acorn planters because they vegetation. Although it is always plantings. cache large numbers of acorns in the helpful to remove competing weeds, Wildlife Enhancement soil but do not retrieve all of them. supplemental irrigation may or may Some of these germinate and develop not be necessary. Average annual Oak environments are among the into seedlings. The presence of wildlife rainfall can also influence whether or richest wildlife habitats in the state; also adds beauty to a woodland and not to irrigate. In areas that receive 110 species of birds use oak habitats value to property. Landowners can less than 15 inches (38 cm) of rain- during the breeding season, and 35 take some measures to increase the fall, watering the first couple of years, percent of California’s land mammals abundance and diversity of wildlife on may be essential, while in areas that utilize oaks during some time of their lands. Here are a few suggestions: receive more than 20 inches (51 cm) their lives. California’s deer herds Leave brush piles in areas where of average rainfall, watering is often are particularly dependent on oak they do not pose a fire hazard. These not necessary. habitats. By maintaining the health environments are used by quail for of your oak woodlands, you promote cover and by small animals for food Maintaining genetic integrity wildlife health and increase the abun- and shelter, and they can provide Regardless of whether you are plant- dance and diversity of both terrestrial nurseries for the natural regeneration ing acorns you collected yourself or and aquatic species. of trees and shrubs. seedlings grown by yourself or others Although a few animals can Large, old trees, especially (e.g., native plant nurseries, youth adversely affect oak seedlings, wildlife deciduous species, are particularly groups, or service clubs), it is impor- generally does not harm mature oaks valuable for wildlife. They have abun- tant to use local seeds for all wildland and often provides important benefits dant foliage for foraging birds and plantings. Local ecotypes, or strains through maintaining ecological insectivorous bats, deeply furrowed of species, have evolved in response to local conditions and are therefore best adapted for survival. Planting off-site material (i.e., acorns collected far from the planting site) is risky since unforeseen events (a rare freeze, for instance) can threaten their survival, even years after the initial planting. Summary Oak regeneration studies to date suggest that the survival and growth of native California oaks in a natural setting are often limited by harsh environmental conditions (McCreary 2001). However, by providing a more favorable environment through weed control, augering, watering, and protective tubes, rapid juvenile growth can be stimulated. This allows seedlings to quickly grow above the level Bob Keiffer where they are particularly vulnerable Mule deer are common residents of California’s oak woodlands. 14 ANR Publication 21538 Living among the Oaks

Shrub cover—that intermediate layer between tree canopy and ground cover—influences the existence of many small animals. It may supply all of life’s requisites for some of these species, such as shrub-obligate birds. Examples of native shrubs that provide cover, as well as food, for wildlife include coffeeberry (Rhamnus californica), toyon (Heteromeles arbutifolia), and manzanita (Arctostaphylos spp.). Shrubs can increase the number of wildlife species inhabiting an area and may also function as refugia for wildlife during extended periods of drought. Manage vegetation for diversity. The diversity of wildlife depends upon the diversity of habitats and age classes Doug McCreary of vegetation. If you maintain a diverse Although oaks are long lived, all trees eventually die. Adequate regeneration is necessary for a species to survive and prosper. structure at the landscape scale (grass- land, woodland, shrubland), as well as a diverse structure at the local scale bark that provides wildlife cover and therefore be retained, unless they pose (tree, shrub, and ground covers), you insect prey, abundant acorns, and a fire hazard or safety concern. encourage a greater diversity of wild- nesting cavities in large limbs and Coarse, woody debris (fallen life. Mixed stands of oaks (i.e., both trunks, both living and dead. Fallen limbs and trees) is valuable for inver- evergreen and deciduous species) are leaves and other material from the tebrate and vertebrate wildlife alike. also advantageous since they provide a canopy provide nutrients under these Among terrestrial vertebrates (birds, greater variety of habitat elements. trees that support a host of soil inver- mammals, amphibians, reptiles), large Wetlands. Probably no compo- tebrates. At the landscape scale, a logs are especially valuable for reptiles nent of oak woodland habitat is more large, lone tree provides connectivity and amphibians. However, recent important for wildlife than riparian between wooded patches, adds struc- research has shown that large wood and other wetland areas. Because of tural diversity, and may provide a safe is in short supply in over half of Cali- the multiple layers of vegetation in stopping point for migrating birds. fornia’s oak woodlands, apparently wetlands (ground, shrub, and tree), Large trees have been referred to as a due to landowner efforts to reduce wetlands support numerous species of keystone species; that is, their ecolog- fire risk and to keep the woodlands wildlife, including many threatened ical benefits are disproportionate to looking clean and well maintained. It and endangered species. However, their numbers. Large dead trees in is therefore beneficial to retain large, wetland areas are particularly sensi- woodlands, called snags, are gener- woody debris whenever possible, as tive to management practices, such as ally rare, but they provide important long as it will not interfere with other intensive grazing, and so they should cavity and perch sites. They should management practices, including fire- be monitored carefully. Oaks along hazard reduction. streams help stabilize the banks, and Living among the Oaks ANR Publication 21538 15

by shading the stream, they help keep Community and watershed the water cool for native trout and COMMUNITY groups. These have developed other fish. If dead oaks or branches throughout California to sponsor a fall into streams, consider leaving ACTIVITIES variety of education, protection, and them if they do not present a flooding Throughout California, landowners woodland enhancement activities. hazard. Woody debris in streams are coming together to solve common These groups pursue public aware- helps to create pools and provides problems in their oak woodlands. ness and educational programs, tree structure and cover for native fish, Many regional problems can only planting projects, registry programs including trout, and for amphibians be solved by landowners working for significant individual trees, and and invertebrates. together in innovative ways. Here are lobbying efforts with local jurisdic- Thinning. Individual oaks and a few examples of landowner efforts: tions to protect a variety of natural groves of oaks can be thinned to meet Landowner associations. In resources, including trees. Two excel- specific landowner needs. Thinning many areas, particularly newer lent examples are the Sacramento can increase residual tree growth, subdivisions, landowner associations Tree Foundation and the Putah Creek stimulate young trees, produce fire- are working on a variety of issues, Council, both of which have been in wood, encourage wildlife, increase including fire safety, regional land- operation for more than 20 years. forage for livestock, and improve scaping, and woodland protection. Carbon Sequestration fire safety. The degree of thinning One excellent example initiated and the selection of trees depend on over 20 years ago is the Portola There is a wealth of scientific data the nature of the woodland and the Valley Ranch, a Hardesty Associates indicating that carbon dioxide objectives of the landowner, but it project. This planned unit develop- concentrations in the atmosphere is important to avoid thinning too ment in the foothills of the Santa have increased dramatically in the heavily. Generally, it is a good idea to Cruz Mountains includes areas of last century. Many believe this leave at least 30 to 40 percent canopy shared oak-woodland open space that will result in climate change and, cover following thinning. are managed and maintained by the more specifically, global warming. Commercial endeavors. Because Ranch Homeowners Association. California has become a leader in of ever-increasing demands of a Open space easements and committing to reduce greenhouse gas growing human population on dwin- dedications of land. In many areas emissions that contribute to elevated dling open space resources, owners of individual landowners, entire devel- atmospheric CO2 concentrations. One rural and semirural woodland areas opments, and local land trusts are new approach has been to promote a can use their lands for a variety of dedicating lands to open space uses cap-and-trade system whereby those commercial ventures that ideally are through conservation easements and generating emissions can purchase compatible with native oaks. Some a variety of other legal tools. Land- carbon offsets equal to the amount potential crops are Christmas trees, owners dedicating such lands often of carbon they emit. Since oak specialty nursery plants, or mush- receive tax relief and, in some instances, woodlands store considerable carbon rooms. You can also open your lands cash payments. Conservation ease- in tree biomass, including roots, for fee-based recreational uses such ments restrict future development but property owners may soon be able to as camping, hiking, hunting, horse- allow normal management activities, sell carbon credits to emitters. While back riding, bird watching, photog- including grazing, farming, and even this approach is new and it is hard raphy, fishing, or mushroom picking. tree harvesting. The Nature Conser- to predict how effective it will be in Increasing income to owners of large vancy, the Trust for Public Land, and reducing emissions, California and woodland parcels may help them the California Rangeland Trust are just its California Air Resources Board retain their properties as wildlands a few of the organizations that operate (CARB) are at the forefront of imple- rather than selling them to developers. such programs, along with many small menting this new approach. community land trusts. 16 ANR Publication 21538 Living among the Oaks

References McMinn, H., E. Maino, and H. Shepherd. Illustration and photo credit given in the 1935. An illustrated manual of Pacific captions. Cover and back photo from Allen-Diaz, B. H., J. W. Bartolome, and M. coast trees. Berkeley: University of istockphoto.com; design by Robin Walton. P. McClaran. 1999. California oak California Press. savanna. In Anderson, R.C., et al., eds., This publication is a revision of Living Savannas, barrens, and rock outcrop Merenlender, A. 1998. Vineyards in an oak among the Oaks: A Management Guide for plant communities of North America. landscape. Oakland: University of Landowners (1995). California Agriculture and Natural Cambridge University Press. 322–339. The University of California prohibits Resources Publication 21577. Allen-Diaz, B. H., R. D. Jackson, and R. B. discrimination or harassment of any person Standiford. 2007. Oak woodlands and Pavlik, B. M., P. C. Muick, S. Johnson, and M. on the basis of race, color, national origin, forests. In Barbour, M.G., T. Keeler- Popper. 2002. Oaks of California. Los religion, sex, gender identity, pregnancy Wolf, and A.A. Schoenherr, eds., Olivos, CA: Cachuma Press, Inc. (including childbirth, and medical conditions Terrestrial vegetation of California, Standiford, R. B. 1996. Guidelines for related to pregnancy or childbirth), physical 3rd ed. Berkeley: University of managing California’s hardwood or mental disability, medical condition California Press. 313–338. rangelands. Oakland: University of (cancer-related or genetic characteristics), ancestry, marital status, age, sexual orientation, Costello, L. R, B. W. Hagen, and K. S. Jones. California Agriculture and Natural Resources Publication 3368. citizenship, or service in the uniformed 2010. Oaks in urban landscapes: services (as defined by the Uniformed Selection, care, and preservation. Standiford, R. B., and W. Tietje. 1990. Services Employment and Reemployment Oakland: University of California Harvesting firewood for sustained yield Rights Act of 1994: service in the uniformed Agriculture and Natural Resources on oak rangelands. Oakland: University services includes membership, application Publication 3518. of California Agriculture and Natural for membership, performance of service, Giusti, G. A., D. D. McCreary, and R. B. Resources Publication 21487. application for service, or obligation for Standiford, eds. 2005. A planner’s Swiecki, T. J., and E. A. Bernhardt. 2006. A service in the uniformed services) in any of its guide for oak woodlands, 2nd ed. field guide to insects and diseases of programs or activities. Oakland: University of California California oaks. Albany, CA: USDA University policy also prohibits reprisal or Agriculture and Natural Resources Forest Service Gen. Tech. Rep. PSW- retaliation against any person in any of its Publication 3491. GTR. 197. programs or activities for making a complaint Giusti, G. A., R. B. Standiford, D. D. of discrimination or sexual harassment or for McCreary, A. Merenlender, and Online Resources using or participating in the investigation T. Scott. 2004. Oak woodland or resolution process of any such complaint. conservation in California’s California Oak Mortality Task Force Web University policy is intended to be consistent changing landscape. White paper site, http://nature.berkeley.edu/comtf/. with the provisions of applicable State and Federal laws. of UC Integrated Hardwood Range California Oak Foundation Web site, Management Program. www.californiaoaks.org/. Inquiries regarding the University’s nondiscrimination policies may be directed to Johnson, S., and W. Tietje. 1995. Wildlife California Native Plant Society Web site, the Affirmative Action/Equal Opportunity among the oaks: A management guide www.cnps.org/. for landowners. Oakland: University Director, University of California, Agriculture of California Agriculture and Natural UC Oak Woodland Web site, and Natural Resources, 1111 Franklin Street, th Resources Publication 21537. http://ucanr.org/sites/oak_range/. 6 Floor, Oakland, CA 94607, (510) 987- Wildlife Conservation Board Web site, 0096. For information about ordering this Keator, G. 1998. The life of an oak. Berkeley: publication, telephone 1-800-994-8849. Heyday Books, and Oakland: www.wcb.ca.gov/. California Oak Foundation. Little, R., T. Swiecki, and W. Tietje. 2001. For Further Information This publication has been Oak woodland invertebrates: The little anonymously peer reviewed for technical To order or obtain ANR publications things count. Oakland: University of accuracy by University of California scientists and other products, visit the ANR California Agriculture and Natural and other qualified professionals. This review Communication Services online catalog at Resources Publication 21598. process was managed by the ANR Associate http://anrcatalog.ucdavis.edu or phone Editor for Agronomy and Range Sciences. McCreary, D. D. 2001. Regenerating 1-800-994-8849. You can also place orders rangeland oaks in California. Oakland: by mail or FAX, or request a printed web-rev-2/11-LR/RW University of California Agriculture catalog of our products from University of and Natural Resources Publication California Agriculture and Natural Resources 21601. Available on the UC Oak Communication Services Woodland Web site, http://ucanr.org/ 1301 S. 46th Street sites/oak_range/. Building 478 - MC 3580 ———. 2004. Fire in California’s oak Richmond, CA 94804-4600 woodlands. White paper of UC Telephone 1-800-994-8849 Integrated Hardwood Range 510-642-2431 Management Program. FAX 510-643-5470 McCreary, D. D., and G. Nader. 2007. Small E-mail: [email protected] parcel landowner’s guide to oak ©2011 The Regents of the University of management. Oakland: University of California Agriculture and Natural Resources California Agriculture and Natural Resources Publication 8263. All rights reserved. Publication 21538 ISBN-13: 978-1-60107-665-6