Station Bulletin No. 90 October, 2008 Updated April, 2010

An electronic publication Western Larch: available at: www.uidaho.edu/ A Deciduous extension/forestry Listed under the Forest- Conifer Management/Silviculture section. in an Evergreen World Dennis R. Parent, Ronald L. Mahoney, & Yvonne C. Barkley

Idaho Forest, Wildlife and Range Experiment Station, Moscow, Idaho.

Director Kurt S. Pregitzer About the Authors:

Dennis R. Parent, Silviculturist, Inland Empire Paper Company, Spokane, WA. Ronald L. Mahoney, Emeritus Professor and Extension Forester, University of Idaho, Moscow, ID. Yvonne C. Barkley, Associate Extension Forester, University of Idaho Extension, Moscow, ID.

Special thanks to the following people for their critical review of this publication:

John Mandzak, Forester, Potlatch Corporation, Lewiston, ID. Chris Schnepf, Area Extension Educator - Forestry, Coeur d’Alene, ID. Mike Wolcott, Consulting Forester, Inland Forest Management, Sandpoint, ID.

Production:

Yvonne C. Barkley, Associate Extension Forester, University of Idaho Extension, Moscow, ID.

Photo Credits:

Cover; page 12: David Restivo, National Park Service. All other photographs were provided by the authors or are from ForestryImages.com

Notes to the reader:

• This publication contains some technical terminology, without which we would have to provide much explanation. If any of the terminology here is unfamiliar to you, please refer to Terminology for Forest Landowners, Extension Bulletin 1353, Washington State University. That publication is available from any Cooperative Extension offi ce in WA, OR, or ID, many libraries, and online at http://cru84.cahe.wsu.edu/cgi-bin/pubs/EB1353.html?id=bEpI8KGe (read and print a PDF fi le, or purchase it for $4.00).

• Herbicide Use. Herbicide recommendations in this publication are generalized information. Any herbicide planning and application must comply with herbicide labels and other regulatory requirements.

This publication is issued as contribution No. 1018 of the Idaho Forest, Wildlife and Range Experiment Station, College of Natural Resources, University of Idaho, Moscow, ID 83844-1130 Western Larch: A Deciduous Conifer in an Evergreen World

Dennis R. Parent , Ronald L. Mahoney, & Yvonne C. Barkley

Western larch is unique. Instead of maintaining their management regimes of the future, and well-suited to needles throughout the winter as other conifers do, a variety of other ecosystem management objectives. larches are deciduous and drop their foliage and grow Its unique qualities among conifers contribute new needles every year. This physiological difference strongly to biodiversity as well. make the larch distinct among the world’s conifer tree species. Few other conifers are deciduous, namely The Characteristics & Ecology of bald cypress and dawn redwood. Western larch Western Larch (Larix occidentalis) is a familiar tree in the Inland Northwest, especially when its fall foliage turns a Range. Western larch has a relatively limited natural brilliant yellow. Many people also refer to this tree range: southeastern British Columbia, central to as tamarack, particularly when used as fi rewood. northern Idaho, western Montana, and northeastern Western larch and subalpine larch (Larix lyallii) Washington (Figure 1). It also is found throughout are the only larches native to the Inland Northwest. the northern Cascade mountain range and in the Subalpine larch exists in small populations in Blue Mountains of northeastern Oregon. There are high altitude locations in Idaho, Washington, and 11 species Montana, and is not suffi ciently represented across Figure 1. Native range of of larch the landscape to differentiate it from western larch in western larch. throughout this publication. Consequently, we will only consider the world. western larch and refer to this tree species as larch Three are through the rest of the publication. native to the United States: Larch is well-adapted to nutrient-poor soils and western larch, burned sites. This shade-intolerant pioneer species subalpine has adapted well to the fi re cycles of its home range. larch found Larch is also relatively resistant to many insects at the higher and diseases common to the region. This is partly elevations of due to its ability to produce new foliage each year. the northern In addition, the wood itself is high in extractives, Rockies, chemicals that help it to resist root-rot and many and eastern wood-rotting organisms. larch (Larix laricina) a Not only is larch exceptionally adaptable as a species smaller tree and resistant to many pests, but it also has excellent in the northeastern United States, Alaska, and Canada wood qualities that make it an outstanding choice that frequents poorly-drained areas. Western larch is whenever strength and consistency are desired. the tallest and largest of the world’s larches. Larch wood is strong, hard, and dense, making it ideal for wood products such as laminated beams, Growth. Western larch is the fastest growing poles, trusses, joists and rafters, and even fl ooring conifer species in the Inland Northwest. Larch and fi rewood. Larch wood fi bers produce good yields effectively competes with other species by rapid for kraft paper. Larch has many qualities that make juvenile height growth. It is common to observe it an ideal wood producer for the intensive forest annual height growth of three to four feet on young 1 plantations with occasional observations of up to as an unreliable fi ve feet. However, larch diameter growth is very seed producer in sensitive to stand density, and if crowded, it loses northern Idaho and crown rapidly because its needles function poorly other parts of its without full sunlight. This property of larch is called range. The reasons “intolerance”. Due to its shade intolerance, larch for this discrepancy usually develops into even-aged stands. are still somewhat of a mystery, although Larch height growth is peculiar compared to other late spring frosts conifers. It exhibits both predetermined and free appear to be the main (indeterminate) growth. Predetermined height growth factor. Consequently, consists of the portion of potential shoot growth for outside of Montana, which stem units were initiated the previous growing natural regeneration season and enclosed in the over-wintering bud. Free of larch is considered growth consists of the portion of the shoot that is Female, risky in most initiated and expanded during the growing season cone-producing fl owers of situations and beyond what was predetermined. In most conifers, western larch in mid-season. planting is preferred. free growth is a juvenile trait that lasts up to 20 years for most species; in larch, free growth continues Tree improvement and tree breeding applies genetic beyond the juvenile phase. This has important principles to develop “better” trees. One of the tools ramifi cations for long-term height growth. of tree improvement is seed transfer. Guidelines have been developed for each western conifer species to Environmental Tolerances. Larch is considered a determine how far seed can be transferred from the “seral” species meaning the tree is very intolerant seed collection site to the planting location. These to low light levels, and is adapted to open, disturbed environmental requirements differ between species. sites. Larch is also a “pioneer species” in that it is one The seed transfer rules for western larch are relatively of the fi rst species to come in after disturbances, such broad, meaning seed and seedlings can be spread as fi re, landslide, fl ood, or clearcut harvest. Compared further from the source compared to other species. to the other conifers in its range, many of which Larch’s adaptation to natural environments with three tolerate partial shade, larch survives and grows only seed zones is intermediate between white pine, which in conditions of high light levels. Whereas all conifers has one seed zone and ponderosa pine, which has six do best in open sunlight, larch can survive only in seed zones across the Inland Northwest. open sunlight. If larch is overtopped by other species its crown rapidly deteriorates, and its vigor declines Nutrition. Little research-based information is severely. Larch is the most shade-intolerant conifer available about larch nutritional characteristics, in the Northern Rockies. This characteristic has many particularly its response to fertilizer, but growth implications for management. response to fertilization is commonly reported. We also know that larch uses nitrogen more effi ciently Larch is “mid-range” in drought tolerance, requiring than other conifers. Larch effectively translocates more moisture than Douglas-fi r and less than western nitrogen from the foliage back into the tree tissues redcedar, for instance. before dropping its needles in the fall and it does this more effi ciently than any other tree genus. For Reproductive Biology and Seed Transfer. Western example, the needle litter of most other regional larch fl owers very early. A warm spell in early- to conifers has about 1 part nitrogen per 16 parts of mid-March can stimulate fl owering. Unfortunately, carbon, whereas larch has only 1 part nitrogen per 50 this peculiar phenology makes the fl owers susceptible parts carbon in its needle litter. to later spring frosts. Water Use. Larch is very water effi cient. It has a Western larch is known to be one of the best seed higher wood production rate per unit of water used producers in northwestern Montana, but it is regarded than other western conifers. However, it can also 2 be considered less water effi cient in that it has only watershed. A forest dominated by larch has less snow moderate drought tolerance. Larch compensates interception than other species due to its open crown for this ineffi ciency by shedding its needles during architecture and deciduous foliage. Therefore, larch the winter, thus not transpiring during its dormant should produce a higher water yield due to less winter months. This could be the reason larch is generally interception and less evaporation loss from the tree not found until we reach the mid-moisture habitats crowns. Larch forests should also experience higher characterized by grand fi r, and larch is most snowmelt rates because of increased wind penetration productive on high-moisture cedar-hemlock habitats. during winter under a bare larch canopy, and more This could also be the reason that larch seedlings sunlight during the early spring before larch leafs seem to be sensitive to moisture, especially in the fi rst out. These characteristics can be an advantage or two to three years of growth and development. disadvantage depending on the goals of the forest manager and a diverse array of other watershed Photosynthesis and carbon fi xation. One of the variables. jobs that trees do well is to remove carbon from the atmosphere and store it as wood and other Aesthetics. There is no argument about the stunning biomass for long aesthetic beauty of larch trees. Larch adds a measure periods. The of color and textural diversity to the viewshed that no photosynthetic other conifer can match. Starting in spring with soft, rate of larch is delicate green foliage which becomes darker green similar to other in the summer, larch really shines in the fall, turning conifers on a leaf brilliant yellow, that in combination with neighboring area basis, but dark green conifers, makes a uniquely striking on a leaf weight landscape. The grays of winter completes the seasonal basis, larch’s net color contrasts in larch forests. Larch produces new, highly productive needles each year. The photosynthetic characteristic “tuft” apperance rates are often makes larch easy to identify. twice that of Special Attributes of Larch other evergreen conifers. In other words, western larch has a low- carbon-cost, well-illuminated, nitrogen-effi cient Fire resistant. Larch is the most fi re resistant species canopy that allocates carbon at higher rates than other in the Inland Northwest (Table 1). Its thick bark western conifers. This information is more easily resists ground fi res, and its open crown architecture understood if one pictures the crown architecture of allows the heat of a fi re to pass through rather than the larch tree. Larch has a large tree height per crown ignite the foliage. Also, if damaged, larch’s deciduous width ratio, which enables the tree to capture higher levels of solar radiation. Its small, short branches Table 1. Fire resistance of Inland allow more of the tree’s photosynthate to be allocated Northwest conifer species. to bolewood rather than limbs or needles. As a result, Species larch can fi x the same or more carbon during its Rank shorter growing season as other evergreen conifers western larch 1 during the entire year. This species is comparably ponderosa pine 2 effi cient in converting light energy to cellulose and Douglas-fi r 3 other forms of carbon. western white pine 4 Watershed values. One of the lesser appreciated lodgepole pine 5 values of trees is watershed protection. A well- grand fi r 6 managed forest protects the land much as a rug western redcedar 7 protects a fl oor. Forests are the best land use to protect western hemlock a watershed. The deciduous nature of larch provides 8 some unique characteristics to the hydrology of a Engelmann spruce 9 3 needles are replaced the following season. Wildfi re fund its genetic improvement through sales from may actually favor larch because the species may seed orchards. still produce a viable seed crop even after the crown • Larch is easy to graft, which improves the is killed by fi re, and fi re, whether wild or prescribed, economics of seed orchards. will likely reduce the competition of other tree species • Larch seed transfer is relatively broad, which and understory vegetation. reduces the cost of seed orchards. • Finally, larch responds positively to intensive Root rot resistant. Larch is relatively root rot forest management, a trait that gives it an resistant. This may be due to a number of factors advantage for capturing the potential genetic including a high level of extractives in the wood improvement. and bark, high phenol/sugar ratios, and low nutrient Wood strength. Larch has strong wood compared to Table 2. Susceptibility of Inalnd Northwest coni- other Inland Northwest conifers. The specifi c gravity fers to root disease (1= highest; 4 = lowest) of wood is highly correlated with strength. Larch has one of the highest specifi c gravities of all conifers Species Armillaria Laminated in this region (Table 3) and larch also has a high western larch 3 2 BTU content, especially if there is a lot of pitch in ponderosa pine 2 4 the wood. Both of these characteristics make larch a lodgepole pine 2 3 preferred species for fi rewood as well as material for laminated beams, fl ooring, and power poles (where western white pine 2 3 ice loading may be encountered) western hemlock 2 2 Engelmann spruce 2 2 Table 3: Specifi c gravity of Inland western redcedar 2 4 Northwest woods. Douglas-fi r 1 1 Species Specifi c Gravity grand fi r 1 1 western larch 0.48 Douglas-fi r 0.46 western hemlock 0.42 demands, which together increase disease resistance ponderosa pine 0.38 (Table 2).Genetic adaptability. Larch has a high potential for genetic improvement and seed orchard lodgepole pine 0.38 development for the following reasons: western white pine 0.36 grand fi r 0.35 • Of the fi ve commercially important Inland Engelmann spruce 0.33 Northwest conifer species, larch has a one of the highest potential volume gains of 20 to western redcedar 0.30 40 percent according to measurements by the Inland Empire Tree Improvement Cooperative from progeny tests in northern Idaho and Height growth. One of larch’s greatest attributes is northwestern Montana. its rapid juvenile (i.e.: fi rst 20 years) height growth. • Larch is also one of the higher-value species and This rapid growth quickly gets the seedling above has held its value over a long period. competing brush and other associated tree species so • Larch exhibits one of the fastest growth rates it can take control of the site. While suffi cient upper- of conifers, especially during the juvenile soil moisture is necessary to enable this growth, its stages, thus recovering investment in genetic fast growth enables its roots to penetrate lower water improvement sooner. levels, sustaining it during drought periods once it is • Larch seed is in high demand because it tends established. to have poor natural seed yields, especially in northern Idaho. Consequently, this may help 4 Windthrow resistance. Larch’s deep and extensive sensitive to competition root system enables it to withstand high winds. Also, and soil moisture the the lack of foliage and light branching causes winter fi rst few years, so gusts to fi lter through the crown, further reducing the control of competing chance of wind breakage or uprooting. vegetation and exposure of mineral soil for Low weather damage risk. Larch is able to natural seedlings are withstand ice and snow loading during the long Inland essential. Northwest winters. This characteristic is mostly due to lack of winter foliage, but a narrow, well-balanced Crowding. Larch’s crown with short branches and strong wood adds to seral, shade-intolerant Larch does well in a mix the ability. Ice and snow loading, especially in the with western white pine and nature causes early spring, may bend the trees, but they usually other conifers, but density rapid crown loss if recover. management is necessary to overtopped or crowded avoid excessive competition by competing trees or Wildlife habitat. Larch snags are long-lived, which for this intolerant species. other vegetation. This makes it one of the best snag species in the west. has implications for the The sapwood is slow to decay and often surrounds timing of precommercial and commercial thinning, the decaying heartwood in older trees with a durable and mixed species management. High tree density can ring of solid wood. This provides excellent habitat for also cause physical crown loss in windy conditions all kinds of cavity nesting birds and mammals. Even because of limb breakage from contact with nearby after the tree falls to the ground its importance to trees. forest growth remains high as it slowly decomposes into long-lasting nutrient and water conserving Herbicides. Larch is very susceptible to herbicide soil organic matter, which is so vital to forest damage. Its non-waxy needles and continuous growth sustainability. with late bud set keeps its tissues susceptible until late fall, whereas other associated conifers begin Chemical value. Larch wood contains many to set bud and go into dormancy during August. extractive chemicals, some of which have marketable Once dormant, conifers are very tolerant of many value. For example, arabinogalactan is a water- commonly used forest herbicides. The exceptions: soluble gum high in sugars that can be extracted larch is quite tolerant to sulfometuron (Oust®), from larch. Though present throughout larch wood, it atrazine (Atrex®) and chlopyralid, effective herbicides tends to concentrate in the butt of the tree, especially for grass and forbs. old ones. In the Libby, Montana, area, many stumps and “long butts” remaining from earlier old-growth Seed Yield. Larch has sporadic cone crops in harvests have been removed and undergone chemical the wild, especially in northeastern Washington extraction. Arabinogalactan, a high-value alternative and northern Idaho. As forest product, is used as a binder in the food, previously mentioned, the pharmaceutical, cosmetic, and bio-tech industries. main reason for poor cone crops is considered to be frost damage to fl owers. Special Problems of Larch Frost does not affect the buds, in fact larch buds are very tolerant to frosts; Although western larch has some unique properties it is the fl owers that are Larch seed is light in that make it one of the most valuable species of the sensitive. Even in years weight with a large Inland Northwest, it also has some characteristics that of good cone crops, seed “wing” that enables it to travel and fall over can be a challenge to its effective management. and cone insects can Regeneration. In order to thrive, larch needs large areas when winds dramatically reduce viable are favorable. adequate site preparation. Regeneration is very seed yields. 5 Mismanagement. One of the biggest threats to parasite dies when the infected plant dies; thus, the sustainable management of western larch is the cutting the tree controls the mistletoe. Mistletoe forester manager. Larch has diffi culty regenerating is a slow spreading disease, so early detection and under the shade of a partial cutting system. sanitation - cutting infected branches or removing Furthermore, if established, larch has even more entire trees - is the most effective treatment. Mistletoe diffi culty growing under the partial shade left after rarely kills large trees, but once established, can kill this type of harvest. Continued high-grade logging, or disfi gure seedlings and saplings. Consequently, partial cutting, public resistance to clearcutting and regeneration may be limited unless infected overstory lack of prescribed fi re may relegate western larch to trees are removed, and because larch regeneration is nothing more than an occasional tree in our forests limited, species composition may change radically in within another rotation. In fact, the biggest threat areas of advanced mistletoe. to western larch may not come from the natural processes operating in the ecosystem, but from human Casebearer. Larch casebearer get its name from the actions and inactions that disrupt natural events. way the larvae carries its cocoon-like case constructed We personally believe that the biggest impact on out of a larch needle as it seeks new foliage to the future of larch is from poor forest management mine. Casebearer was decisions, often driven by “kinder and gentler” accidentally introduced sentiments that particularly effect management of into the U.S. in the public lands. These concerns could be moot, however, 1950’s. It spread rapidly if recent research on the relationship between the and reduced larch growth range of larch and climate change proves true. One dramatically during the model predicts that the present trends in climate 1970’s and early 1980’s. change could result in a large portion of larch’s Introduced and native current range becoming unsuitable over the next parasites, plus adverse Once a plague on Inland 30 to 90 years. We don’t want larch to eventually Northwest larch, the weather conditions, casebearer damage shown become a threatened species simply due to poor forest appear to be reducing here has become rare due management, but we also need to be thinking of how the casebearer problem. to parasites of this intro- we respond to changing environments and habitats for Spotty outbreaks still duced insect. this and other forest tree species. occur in certain areas, but the insect pest is now generally “endemic” (it Insects and Disease. Western larch is relatively free maintains a small, incidental population). of damage from most insects, diseases, and other problems. However, larch is susceptible to some Needle Cast. Larch needle cast (Meria laricinis) and pathogens and insects. The important ones are listed needle blight (Hypodermella concolor) are caused by in Table 4 and are addressed below. naturally occurring fungi. They can cover large areas after warm, wet winter weather conditions. Although Mistletoe. Dwarf mistletoe is probably the most damaging pathogen of larch. Table 4: Western larch insect, disease, and other problems Mistletoe is a parasitic plant that grows on the tree, removing sap Name Species Relative Importance for its sustenance. Swellings on dwarf mistletoe Arceuthobium laricis 1 the limbs and dense branching larch casebearer Coleophora laricella 2 that later become visible as needle cast Meria laricinis 3 “witches’ brooms” are the visible effects of mistletoe. Dwarf bears Ursus americanus 4 mistletoes are species specifi c; spruce budworm Choristoneura occidentalis 5 the same species of mistletoe root and butt rot Phaeolus schweinitzii 6 cannot infect different species laminated root rot Phellinus weirii 7 of trees. It is easy to deal with silviculturally because the fl atheaded fi r borer Melanophila drummondi 8 6 the impacts may appear serious and from a distance Natural Regeneration. Natural regeneration can be are easily confused with casebearer, these pests have successful for larch, but it is not easy, free, or cheap. minor impacts under normal conditions. In addition, natural regeneration is usually a higher fi nancial and biological risk than planting. For the Budworm. Western spruce budworm will damage greatest chance of success, it requires a broadcast larch only if there is no other nutrition available and burn or intense site preparation, which can include the population is epidemic. either mechanical or herbicide methods, or Root Rot. Although rare, larch will occasionally both. The highly periodic become infected with root rot, but even when cone crops require a infected, the disease usually manifests as butt rot and method of prediction. the tree is rarely killed. When root rot centers develop In Montana, researchers for other conifer species, planting larch is often found that the probability recommended where conifer regeneration is desired. of natural stocking for any species is less than Bark Beetles. Historically, bark beetles have not been 50 percent. Even with a problem for western larch. However, the fi rst known scarifi cation you must instance of bark beetle-caused mortality was recently be willing to accept this discovered in Montana. Although trees were killed, risk, and understand that foresters believe the outbreak was indirectly caused for full stocking at least by recent droughts and some spot planting is wildfi re. nearly always required. Leaving well-formed, domi- Furthermore, pre- nant larch for natural seed- Animal Damage. One of commercial thinning of ing is a common and effective regeneration method. the more serious problems naturally overstocked of larch is the stripping areas may be necessary of bark by bears. During to secure the investment and capture the full growth spring, when other food potential of larch. is scarce, the bears strip pole-sized trees to get There is a technique to enhance cone production in at the succulent inner natural stands. Research at the USDA Forest Service bark. Some feel that this Rocky Mountain Research Station developed a is a learned response method of partial girdling that increased larch cone and animal control can Bear damage is a crops signifi cantly. The dominant trees in a stand must be effective, while other localized, but be partially girdled in March before fl owering occurs. forest owners have tried sometimes severe, Make two saw cuts three-quarters of the way around feeding stations at critical problem for the tree opposite each other and spaced apart about times with mixed results. pole-sized larch. equal to its diameter on the tree bole. This wounding For some unknown reason, has little effect on the health of the tree, and will not the bears seem to prefer larch over other tree species. kill it or attract bark beetles or other insects, as it It has been speculated that this is due to the additional might in other species. This tactic can be applied in sugars contained in larch trees. seed tree systems where these “parent” trees would be removed within 10 years after seedling establishment. Silvicultural Treatments for Western Larch Planting. Artifi cial regeneration provides a much higher guarantee of success if good seedlings are The silvicultural treatments for western larch are available from proper seed zones. Site preparation fairly straightforward if the forester recalls the is just as important as with natural regeneration. previous ecological requirements and characteristics Prescribed fi re, mechanical treatment, herbicides or a of larch and uses them to fi ne tune the prescription. combination of these can be used. The most important 7 thing to remember - if good survival is desired, planting to allow its there must be adequate site preparation that removes activity to degrade. or reduces competing vegetation. Plant as large a Thinning. Thinning seedling as you can afford. Many people are changing can favor the best to bigger seedlings with Styro-8 container-grown species, optimize seedlings currently the most popular. Larger seedlings biological growth, have higher survival and are better able to withstand increase future animal damage and the other hazards of nature. income, and provide Bigger seedlings cost more, but remember, the issue many other benefi ts. is not planting cost but cost per survived seedling. Considering the The higher cost of bigger seedlings is generally offset recent emphasis on by better survival, reducing the need for subsequent smaller stems (with re-treatment of the site and re-planting. minimum sawlog diameter at the small Fall planting may be preferable to spring, but only The absence or control of end approaching if container stock is planted early enough in the fall competition is essential for four inches) thinning successful larch to allow signifi cant root growth. Root growth during regeneration. is less important, fall predisposes the seedling to start crown expansion especially since small immediately when the weather warms the following tree harvests mean shorter rotations, earlier monetary spring. However, do not fall plant larch on frost-prone returns, and higher net present values. sites, especially those with fi ne-textured silt and clay soils, due to the danger of frost heaving. Avoid sites Precommercial thinning. Precommercial thinning exposed to strong winds and areas with a traditional can be an effective silvicultural treatment for larch lack of winter snow, because soil moisture is critical with the following considerations: in winter as well as summer. Fall planting is best when there is suffi cent available moisture on higher • Thin early - at 10 to 15 years old and 15 to 20 elevations and northerly aspects. feet tall, before signifi cant crown loss occurs. This results in lower cost, larger crowns, and Since larch is very sensitive to any amount of better growth response. It also produces less competition, vegetation control is a vital ingredient slash and lower fi re hazard than later thinning for regeneration success. The best advice is to get of larger trees. it done before planting the seedlings. Due to larch’s • Thin from below to leave the best crop trees. sensitivity to most herbicides, it is very diffi cult to The key is to look for the trees you want to treat seedlings after planting. Use contact herbicides leave at the desired spacing, then cut the rest. such as glyphosate (Roundup®, Accord®, Foresters®) • Select the spacing carefully to get a diameter and imazapyr (Arsenal®, Chopper®) prior to planting. growth rate that will allow merchantable trees Atrazine (Atrex®), acting as a preemergent herbicide, to be cut in the next entry. can help hold sites after contact herbicide treatment. • Remember, the greatest volume growth is Chlopyralid, a relatively new herbicide, can control found at medium to high tree densities. In thistles that tend to seed into sites about a year after other words, you may sacrifi ce maximum treatment with the above herbicides. Sulfometuron diameter trees to achieve the highest volume (Oust®) herbicide may work but be mindful of soil per acre at the next harvest. pH. The solubility of Oust® increases rapidly once the • oo high a thinning cost can result in a poor pH is above 6.0. As solubility increases, so does the investment. For example, a $150/acre thinning chance for damage. Oust® job today invested at a four percent real herbicide works well on established grasses, and interest rate must generate an additional two to most of our forest soils are suffi ciently acidic to avoid three MBF per acre in 30 to 40 years in order the solubility problem. Fire, or planting on formerly to recoup the initial investment. farmed land, may raise soil pH. In these situations, it • Leaving too wide a spacing wastes growing is better to apply Oust® 6 months or so in advance of 8 space, with trees eventually getting too big strength, especially in western larch. Wood strength by the time they can economically utilize the (as measured by density or specifi c gravity) is affected area. Keep in mind that big trees are no longer more by the ratio of summerwood to springwood, not more valuable than several small trees of merely by ring width. Thinning often increases the equal volume. summerwood to springwood ratio because the trees • Thinning too late can result in poor response have more adequate moisture through the drier part of because crown loss from early crowding the summer season. Thus, you can have wider growth leads to growth loss. Sometimes, the crown rings and stronger wood, or more volume and better can eventually rebuild, but the best thinning wood quality. is one that occurs before the trees lose any growth potential. Thinning must be completed In 2004, research on the Coram Experimental before the tree crowns are reduced to less Forest in Montana found no signifi cant differences than 40 percent of the total height to maintain in average wood density between a wide range of optimum growth. thinning densities (110 to 680 trees per acre). In addition, there was strong evidence that managed Commercial thinning. Commercial thinning in pure larch stands will produce a larch stands can be questioned from either economic relatively high proportion or biologic terms: of mature wood (vs. the higher proportion of • It can open up the juvenile, weaker wood stand to brush associated with young competition. or thinned trees of other • It can result in loss of conifer species) with total stand growth. relative density levels • It may encourage similar to natural forests. larger trees that are This wood density effect worth less in today’s is unique to larch; other log market. western conifers do not The short growth grow this way. Another But, the landowner may internodes show the wood quality characteristic effects of competing have other objectives vegetation of which is unique to larch is that can be met using this tree. the ring density variation commercial thinning: within the tree bole. Larch Vegetation ring density increases uniformly from pith to bark, management helped this • Favoring larch in whereas other conifers decrease at fi rst, then increase. 8-year old larch reach a mixed composition This has positive implications for wood quality, its growth potential. stand, where other especially wood quality in managed stands with species such as grand fi r smaller diameters. Not only do these characteristics may be less desirable. make larch wood stronger overall; it is also less • Minimizing losses to insects or disease. prone to warping, and shrinking erratically than other • Growing desired diameter trees in a shorter species. amount of time. • Opening up the stand for additional structural Pruning. Due to larch tree biology, wood quality and vegetation diversity. characteristics, and log market specifi cations, there • The aesthetics of a more open-grown stand. is little need to prune western larch for the following • Earlier income generation. reasons: • Increasing maximum harvest yield. • Larch self-prunes well, especially if kept Thinning and wood quality. There is some recent dense at young ages. good news about the effects of thinning on wood • Larch tends to produce epicormic branches 9 from dormant buds on the bole. These buds The goal of the selection harvest system is to produce respond to the increased light after pruning. or maintain an uneven-aged stand. This is a diffi cult • Larch is primarily used for construction and challenge, especially if the stand is currently even- dimension lumber. The grading rules for aged as many of our Inland Northwest forest stands construction lumber allow up to two-inch are. Selective cutting, on the other hand, is a general green knots without large decreases in grade term used by people who hope to legitimize a partial or strength. Therefore, reduction in knots or harvest that may or may not be best for the stand. A knot size is less important than with lumber thinning is a selective cut that can be very appropriate used for appearance grades (ponderosa pine and benefi cial, or detrimental as in a diameter- and white pine). limit or high-grade harvest. A main difference in a thinning compared to a selection harvest system, is However, there may be some economic and health that thinning is not intended to induce regeneration, reasons to prune larch along roads and other possible whereas the selection system has that as a necessary fi re ignition zones, to reduce the chances of a ground objective. fi re “climbing” into the crowns of younger larch stands. Often, individuals use diameter as a surrogate for age, since diameter is easier to measure. However, Fertilization. There is limited information on larch larger diameter does not always indicate increased nutrition and fertilization. One recent study of the age, particularly in a multi-species stand where the ten-year effect of fertilization on tree growth and diameter variability is usually a result of species, mortality found no signifi cant fertilizer effects on competition, or genetic differences, not age. Cutting western larch. Another fertilization project resulted only the larger trees in hopes of developing an in a large early growth response, but there was a uneven-aged stand usually results in a degraded rapid falloff the next year. This does not mean that stand with large amounts of smaller trees that grow fertilization may not be a viable option for larch in more slowly. Even in single species stands, this is the future, as new formulations are tested and fi eld an equally detrimental practice, since diameter size trials are expanded to more sites. Properly prescribed is greatly effected by proximity to competing trees fertilization can also stimulate and enhance fl owering regardless of species. and cone production. After reviewing the silvics of larch, it should be apparent that an uneven-aged stand of this species would be extremely rare, if it exists at all. Since larch has great diffi culty regenerating and growing Harvest Systems for Western Larch under conditions of low light, a selection harvest system will most likely end in failure. It is possible to manage larch under the group selection system, IF the Selecting the correct harvesting system for a gaps for groups of regeneration are large enough. For species is more than just the most economical instance, gaps an acre or more in size, would leave method of getting the trees to the sawmill. It is also an uneven-aged stand across a large area, but there a silvicultural system designed to regenerate the is little reason to do this with larch, and many would species. Understanding the silvics and biology of consider this a series of small clearcuts rather than a larch helps design successful harvest systems that “selection” system. Nonetheless, this type of group simultaneously complete the growth of one stand and selection system may be the best choice when visual begin that of another. Consider larch and the four or political factors favor a more complex, costly main timber harvest systems: management regime.

Selection. Selection cutting is a misunderstood and Shelterwood. Regenerating larch using the often misused term. The term selection cutting is shelterwood harvesting system can work if the often used interchangeably with “selective” cutting. tree crowns are opened up suffi ciently. This means Silviculturally, the two terms are very different. leaving less than 40 square feet of basal area for the shelterwood. Of course, one must consider the risk 10 of wind damage before using this system, and at adapted associates such as western white pine and this density, many would just consider it a seed tree ponderosa pine. But there are many things to consider. system. The following mnemonic may help to recall the main Seed tree. The seed tree harvesting system works principles: quite well for larch, especially if the site is prepared using prescribed fi re after harvest. A good cone Look for Seed. crop and adequate site preparation allows natural Adequate Site Preparation. regeneration to prosper. If natural regeneration fails, Realize the Importance of Planting. the planting option can be used but would likely Control Density. require additional site preparation. Heavy Harvest

Clearcut. The clearcutting harvest system is Look for Seed. Plan for seed needs in advance. favorable for larch because it creates conditions that Look for seed crops in seed production areas. Girdle are closely aligned with its silvicultural requirements. individual trees for cone production in March of the A large clearcut is not necessary; neither is complete previous year. Find good sources of seed for nursery tree removal or intense site preparation. But overhead seedlings such as your own elite trees, logging jobs, shade and plant competition must be minimized using or by purchase. The Inland Empire Tree Improvement an appropriate silvicultural technique. A clearcut size Cooperative (IETIC) has signed a contract for the of 15 to 20 acres or more with the amount of edge development of a larch seed orchard at Vernon, minimized by a square or circle shape will regenerate British Columbia. Improved seed should be available larch effectively. within 10 years to IETIC members, private nurseries, If landowners desire to and the general public. regenerate larch, the harvest must allow large amounts Adequate Site Preparation. This step is very of light to reach the ground important for initial success of planted or natural surface. Also, adequate site seedlings. Site preparation can be accomplished preparation and control of using prescribed fi re (broadcast or underburn), competing vegetation is careful mechanical scarifi cation with minimal critical. One must cut hard soil compaction and displacement, or herbicide and plan well to regenerate treatments. Select an herbicide with no residual soil larch. It will be diffi cult to activity; an Accord®/Arsenal® herbicide mixture may maintain a signifi cant western work best. Herbicides can be applied using broadcast, Where larch has larch component in our strip, or spot methods. become rare, Inland Northwest forests if individuals with there are no fi res or clearcuts. good crown Realize the Importance of Planting. Larger seedlings characteristics can Additionally, site preparation be left as seed trees. and post-establishment such as Styro-8’s (8 cubic inch container) seem to control of competition using work well. Also, copper treated containers are a appropriate herbicides and/or prescribed fi re and defi nite advantage for rapid root egress once planted mechanical methods need to remain acceptable and adequate fi rst season moisture is essential. Good options on many sites, or larch will simply be site preparation should exclude the need for further overwhelmed by other tree and plant species. herbicide treatment but spot treatment with Oust® can be used if the soil pH is less than about 6.0. Consider planting in the fall rather than spring to take The “Secrets” of Growing Western Larch advantage of increased soil moisture availability and early root growth. Generally, fall planting requires There is really no secret in growing a successful larch soil temperatures at or above 40 degrees F for forest, which may be a pure larch stand or a mix with successful root growth. With fall planting avoid early frost zones to reduce frost heaving of seedlings. 11 Control Tree Density. The best time to control density combined with other compatible species, usually is at planting time. In the Inland Northwest, it is not western white pine and/or ponderosa pine, and even usually necessary to plant more than 200 to 350 trees cedar in some cases, where a more mixed species per acre. On diffi cult sites, many will plant more trees composition is desired. However, the larch in these per acre. However, this often produces overstocked situations will not thrive unless specifi c light and patches and still leaves open areas. It may be better moisture requirements are met. to plant again the following year in unstocked gaps to get the best distribution of established larch seedlings. Precommercial thin if density is over 1,000 trees per Summary acre. When thinning, don’t forget today’s value of small logs. Remember, you are making an investment that has to return a profi t 20 to 40 years in the future. Western larch is a tough tree that is resistant to insects Do not plan on commercial thinning in larch stands, and diseases. Its excellent high density, straight- except where other objectives compliment or replace grained character produces wood that is hard, strong, timber objectives. Keep stand density high enough and durable. Its deciduous foliage protects it against to suppress undergrowth but low enough to develop many of winter’s onslaughts. Larch grows rapidly, healthy crowns and merchantable sizes. and as a long-lived seral tree, dominates many fi re- climax landscapes. Its unique qualities suggest that Heavy Harvest. To obtain successful regeneration, it can do very well under the intensive management a heavy harvest will help to produce the ecological regimes of a future where we grow more wood on conditions which set the stage for adequate larch fewer acres. A little care during planting and early regeneration and growth. That usually means a seed growth will pay big dividends as the tree matures. tree or clearcut harvesting system. Remember, if you Larch is truly a tree that deserves our attention, for it cannot cut hard, you cannot manage for maximum presents opportunities for the future unlike any other production of pure larch stands. Larch can be Inland Northwest conifer.

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