HOUSTON

The Garden Club of Houston Hermann Park Conservancy The Houston Parks Board TOUGH Katy Prairie Conservancy Lady Bird Johnson Wildflower Center Memorial Park Conservancy TREES HOUSTON

TOUGH TREES

summer 2012 Tough Texas Trees for Houston

PREFACE In selecting trees for Houston region, it is important Although the change in Houston’s climate over the to remember that we do not know what weather previous three years–moving from a generally wet patterns our region will face in the next few years. climate at approximately 45 inches of annual rainfall It would be unwise to simply select trees from else- to less than 20 inches of annual rainfall–was begin- where that are impervious to drought, as they may ning to be seen, no one anticipated how devastating not tolerate our local soils or the enormous rain that the 2011 summer of record heat and drought would be Houston can be subject to. So, we have emphasized for our trees. here the trees that are both native to our region and A generous gift from The Wortham Foundation, drought tolerant, and thus more likely to survive in Inc., brought the parks and greenspace community all rainfall conditions we may face. Other trees that together to assist the City of Houston. While the City are native to other, usually drier, parts of the state are put tremendous resources into removing dead wood identified separately as they have also done quite well for public safety and fire hazard reasons, we joined the here as long as they are given good drainage. City in saving as many trees as possible and planning Particularly as our climate changes, it is important for the future. to select a diversity of trees that provide food and The immediate response was focused on legacy trees, shelter to the birds, butterflies, and other wildlife those significant because of historic location or size, that enrich our area, so we have also provided infor- and on younger trees with a higher likelihood of sur- mation on which of these trees are particularly useful vival. We treated the root systems of targeted legacy to wildlife. trees for better water and nutrient absorption, and wa- All the experts emphasize how important good plant- tered as much as funding and practical considerations ing techniques and supplemental watering are to allowed before winter dormancy and in the critical establishing trees under dry conditions. So, planting early spring period. Thankfully, spring 2012 turned out tips are included here also. to be average in terms of rainfall. We hope that these lists are helpful to Houstonians Now we look to the future and to replanting. Know- as we together recover from the drought of 2011 and ing what did well under severe drought conditions plant for the future. is important to choosing what trees to replant. This booklet reports the 2011/2012 experience and judg- ment of many of our region’s agencies who manage large public spaces, of expert professional foresters and nurserymen, and of avid gardeners. We are grate- ful to all the experts who helped to create these lists; The Garden Club of Houston all are listed along with other information sources at Hermann Park Conservancy the end of the guide. The Houston Parks Board Katy Prairie Conservancy Lady Bird Johnson Wildflower Center Memorial Park Conservancy LARGE TREES These large native trees were observed to, once established, survive the historic 2011 drought with little or no supplemental watering. HOUSTON

LEGEND

LARGE SUN TREES PARTIAL SUN

SHADE

ATTRACTS BUTTERFLIES

ATTRACTS BIRDS tough TREES LARGE TREES

Bur Oak Quercus macrocarpa Platanus occidentalis American Sycamore

Soil: variety of soils, sand, Soil: moist, sandy loam or loam, clay, or caliche silty clay Growth Habit: deciduous; Growth Habit: deciduous; easy and fast-growing; fast-growing and long-lived; resistant to drought, urban broad, dense crown with pollution, fire, insects and very large leaves that are disease; straight trunk bright green on top and with a broad, rounded paler underside; has distinc- crown of stout branches tive, white, exfoliating bark; Flowers/Fruit: largest larger trunk diameter than acorns of all native oaks any other native hardwood Size: 80 feet tall or more Flowers/Fruit: brown balls of small seeds, 1 inch in di- ameter on 3 to 6 inch stems Size: large tree up to 100 feet or more

Live Oak Quercus virginiana Platanus mexicana Mexican Sycamore

Soil: gravel, sand, loam or Option to American Sycamore clay but does best in neutral The Mexican Sycamore or slightly acid clay loam is a close relative of the Growth Habit: evergreen; American Sycamore and fast-growing and long-lived; is very similar. It averages very resistant to salt spray; 80’ by 50’, fast-growing, full easily transplanted when sun, tolerant of most soils, young; tolerates poor drain- tolerates wet and drought, age and compaction of soil long-lived. It is native to Flower/Fruit: acorns about Mexico but is now being 1 inch long planted in the Houston area. The Mexican Syca- Size: large spreading tree more is preferred to the to about 50 feet tall with a American by many nursery crown of up to 100 feet in people who feel it is more diameter disease tolerant than the American Sycamore, but time will tell whether this is accurate. tough TREES LARGE TREES

Pecan Carya illinoinensis Taxodium distichum Bald Cypres

Soil: rich, moist, well Option to the Montezuma Cypress drained soils, sand, loam, Bald Cypress is more eas- clay or caliche ily found in the trade and is Growth Habit: deciduous; frequently planted in street fairly rapid growth; excel- medians because of its adapt- lent shaped tree with thick ability to soil and water con- straight trunk, broadly ditions. Bald Cypress knees rounded crown; tolerates can be a problem in poorly poorly drained sites; State drained areas, but the knees Tree of Texas can be controlled by cutting Flowers/Fruit: oblong nut them off with a pruning saw ripening in fall about 1 inch below the soil Size: 70 to 100+ feet tall, surface. The bald cypress is allow plenty of room for deciduous, and the soft, ferny growth leaves turn terra cotta hue in the fall.

Montezuma Bald Cypress Taxodium mucronatum Ulmus alata Winged Elm

Soil: wide variety of soils, Soil: wide variety of soils, sand, loam, clay sand, loam, clay, caliche Growth Habit: evergreen Growth Habit: deciduous; or semi evergreen; fast- fast-growing shade tree growing and long-lived; with spreading branches needle-leaf, tall straight and rounded top; small trunk, broad crown with serrated dark double ser- spreading branches and rated, green leaves that drooping twigs, few or no turn yellow in the fall knees, tolerates extended Flowers/Fruits: samara flooding and well drained (winged seed pod) Flowers/Fruits: cone bear- Size: 40 – 70 ft. tall ing plant, cones open in February and seeds ripen in October Size: 36 to 80 ft. tall tough TREES LARGE TREES

Cedar Elm Ulmus crassifolia Quercus stellata Post Oak

Soil: wide variety of soils, Soil: rocky or sandy soils, sand, loam, clay, caliche acid based Growth Habit: deciduous; Growth Habit: deciduous; fast-growing and long- slow-growing and long-lived; lived; large, rounded-crown broad, rounded crown with shade tree with drooping thick, sometimes leaning, branches; dark-green leaves trunk; few pest problem; are small, rough-textured does well soggy soils, ex- and yellow in fall; tolerates tremely drought tolerant alkaline soil but roots are very sensitive Flowers/Fruit: samara to being disturbed (winged seed pod), autumn Flowers/Fruit: small acorns, fruiting different from most ¾” to 1 ¼”, ripen in the fall other elms Size: 50+ ft. tall Size: 30 to 60 ft. tall

Eastern Red Cedar Juniperus virginiana var. virginiana Ulmus americana American Elm

Soil: wide variety of soils, Soil: well drained, variety sand, loam, clay, caliche of soils, sand, loam, clay, type will tolerate salty soil Growth Habit: fragrant Growth Habit: deciduous; evergreen conifer; cone fast-growing and reason- shape when young but ably long-lived; attractive, more irregular shape when tall shade tree with a sym- older; fluted trunk up to 2 metrical crown of spread- ft. diameter with reddish ing branches that arch and brown, thin bark that peels droop at the tips; thick off in long strips trunk usually divides into Flowers/Fruit: pale blue several large ascending, berries on female plant, erect branches; double ripen September to serrated leaves are 3 to 6 December inches long and very rough on the top surface Size: can get to 70 ft. tall, depends on soil and sight Flowers/Fruit: clusters of conditions single seeds, mature by early summer Size: up to 80 ft. tall tough TREES LARGE TREES

( NATIVE TO DRIER AREAS ) LARGE TREES The following large trees were also observed to survive the 2011 drought with little or no watering. They are native to drier areas south and west of Houston and do well here only if they have good drainage.

Green Ash Fraxinus pennsylvanica Quercus muehlenbergii Chinkapin Oak

Soil: adapts to a variety Soil: rocky or sandy soil, of soils, sand, loam, clay alkaline Growth Habit: deciduous; Growth Habit: deciduous; upright, spreading habit moderate to fast-growing; with crown shape varying straight trunk with light from irregular to symmet- colored bark and spread- rical rounded; deep green ing crown; attractive summer foliage; relative saw-toothed leaves turn freedom from insects and yellow to bronze color in diseases the fall; seldom troubled Flowers/Fruit: samara by diseases or pests (winged seed pod) on Flowers/Fruit: acorn ½” female tree, large seed up to 1 ¼ ” long crops Size: up to 50 ft. tall Size: 50 to 70 ft. tall tough TREES LARGE TREES

HOUSTON

Mexican White Oak (Monterrey Oak) (Quercus polymorpha) Soil: wide variety of soils but best in well drained alkaline soils Growth Habit: deciduous to semi-evergreen; fast-growing SMALL - tall at first then spreads its crown; light colored bark; deep green, long, oval leaves 5”-7” creates a lush TREES appearance and has reliable fall color; resistant to oak wilt, diseases and pests; as drought tolerant as the Live Oak once established Flowers/Fruit: medium size acorns Size: 50 ft. tall tough TREES LARGESMALL TREESTREES

SMALL TREES Mexican Plum Prunus mexicana Once established, these small Soil: sand, loam, clay Growth Habit: deciduous; trees were observed to survive moderate to fast growth; highly drought tolerant, the historic 2011 drought with tough tree; single trunk with bluegray bark, dark little or no supplemental watering. horizontal striations and broad crown Flower/Fruit: fragrant, showy, white flowers appear before leaves, followed by small, round, purple fruit Size: 15 to 30 ft. tall, 25 ft. width

Texas Redbud Cercis canadensis var. texensis Crataegus marshallii Parsley Hawthorn

Soil: sand, loam, and clay; Soil: sand, loam, clay; toler- will not do well in low, ates seasonal poor drainage wet area Growth Habit: deciduous; Growth Habit: deciduous; slow growing but long- fast-growing lived; multi-branched, some Flower/Fruit: In March branches have thorns; ½ inch clusters of pink leaves look like parsley; flowers appear before plant more than one tree leaves, followed by for better fruiting seed pods Flower/Fruit: showy, 1 inch, Size: 10 to 20 ft. tall white flowers, followed by small red haws (berries) throughout winter Size: 15 to 30 ft. tall, 25 ft. width tough TREES LARGESMALL TREESTREES

Yaupon Holly Ilex vomitoria Viburnum rufidulum Rusty Blackhaw Viburnum

Soil: sand, loam, clay; Soil: sand, loam, clay; tolerates seasonal poor well drained soils only drainage Growth Habit: deciduous; Growth Habit: evergreen; slow growing; shrub for a fast-growing; can be long time but becomes a pruned into multi-trunk single trunk tree with broad tree or hedge; spreads crown; can be difficult to aggressively in non-main- start but beautiful once tained areas; need male established, with glossy and female to have berries green leaves with fall color Flower/Fruit: insignificant Flower/Fruit: 4 in. white white flowers in spring, flower clusters in spring, followed by red drupes followed by ½ inch long (berries) on female trees blue/black drupes in fall in fall and winter Size: 10 to 30 ft. tall, up to Size: 12 to 25 ft. 35 ft. wide

Possumhaw Holly Ilex decidua Morella cerifera (Myrica cerifera) Southern Wax Myrtle

Soil: sand, loam, clay; Soil: deep sand, loam, clay; well drained preferred but adaptable, will tolerate poor will tolerate seasonal poor drainage once established drainage Growth Habit: evergreen; Growth Habit: deciduous; fast-growing; keep moist moderate growth; will fruit when first planted, drought best in more sun and must tolerant once established; have male plant nearby large shrub that can be Flower/Fruit: Small white maintained as hedge or flowers in spring, followed small multi-trunked tree by bright red-orange drupes Flower/Fruit: inconspicuous on female plants that persist flower, followed by pale blu- into the winter and are ish berries along branches of showy on bare branches female plants Size: 8 to 20 ft. Size: 10 to 20 ft. tall, 10 to 15 ft. wide tough TREES SMALL TREES

American Holly Ilex opaca ( NATIVE TO DRIER AREAS ) SMALL TREES

Soil: sand, loam, acid soils; must be well drained (if you Several trees that are native to have clay—use ‘Savannah’ drier areas west of Houston can cultivar) Growth Habit: evergreen; be successfully grown here and slow growing but long- lived; triangular crown that have done well in the record broadens with age; good for drought. Typically, these trees screening Flower/Fruit: require excellent drainage, so care inconspicuous flowers, followed by red berries should be taken in choosing a site. on female, need a male tree Seven such trees that have done nearby for pollination Size: 15 to 35 ft., well in Houston in general and occasionally to 60 ft. during the drought are:

Mexican Buckeye Ungnadia speciosa Cordia boissieri Texas Wild Olive

Soil: wide variety of soils Soil: variety of soils from from rocky and caliche to caliche to clay; must be well clay; must be well drained drained Growth Habit: decidu- Growth Habit: persistent ous ; fast-growing; often to evergreen; fast-growing; multi-trunked, makes an sensitive to cold—will freeze attractive understory tree to roots below 20 degrees; with yellow fall color drought tolerant once estab- Flower/Fruit: clusters of lished; rounded crown with bright-pink, fragrant flow- short trunk ers appear before or with Flower/Fruit: showy 2 inch the leaves in the spring, white flowers with yellow followed by reddish brown throat, followed by drupes 3 lobed buckeyes contains (berries) that are white turn- several dark brown shiny ing to purple; will flower seeds almost all year with enough Size: up to 30 ft. tall, but water usually smaller Size: 12 to 24 ft. tall, 25 ft. wide tough TREES LARGESMALL TREESTREES

Jerusalem Thorn (Retama) Parkinsonia aculeata Sophora secundiflora Texas Mountain Laurel

Soil: sand, loam, clay, cali- Soil: prefers dry, rocky soil che; must be well drained; but will grow in sand, loam, does well in disturbed soils or clay if well drained and poor soils Growth Habit: evergreen; Growth Habit: deciduous; slow growing medium fast-growing; spiny small size tree; highly drought tree with long, graceful, tolerant slightly drooping branches Flower/Fruit: fragrant, with unusual green bark showy violet pea-like bearing many long, deli- flowers in clusters at the cate leaves, leaves often tip of branches in spring, fall off in the summer followed by hard pods 3 ½ Flower/Fruit: profusion of to 5 inches long with shiny yellow flowers in the warm red seeds inside; seeds are months, especially after highly poisonous a rain, followed by 2”-4” Size: up to 30 feet tall legumes Size: up to 30 ft. tall

Wright Acacia Acacia greggii var. wrightii Diospyros texana Texas Persimmon

Soil: caliche, limestone- Soil: well drained, lime- based, sand, loam, clay stone loam, clay, caliche Growth Habit: evergreen to Growth Habit: decidu- semi-evergreen; slow grow- ous; slow growing; small ing; highly drought tolerant; tree with rounded crown, requires pruning to develop smooth gray bark and one or more main trunks; small leathery leaves; feathery leaves and cat highly drought tolerant claw-like thorns on twigs, Flower/Fruit: urn shaped, highly insect and disease white, single or small resistant. clusters of flowers in Flower/Fruit: fragrant March and April, followed white bottlebrush-like by small edible fruits on spikes, followed by small female trees that turn brown seed pods 1” to 6” black when ripe from late Size: 30 ft. tall and 35 ft July into September. wide Size: up to 35 ft. tall tough TREES LARGESMALL TREESTREES

Anacua Ehretia anacua

Soil: well drained, variety of soils, alkaline soils, sand, loam, clay Growth Habit: semi- evergreen; rounded crown with rough-textured leaves; requires pruning to develop one or more main trunks; needs a lot of water to get established, but is highly drought tolerant thereafter HOUSTON Flower/Fruit: fragrant white flower clusters cover tree in spring, followed by edible, quarter-inch orange fruits that ripen April to June Size: up to 50 feet

Texas Ash Fraxinus texensis

Soil: prefers loamy, well drained soils, but works well on dry sites with sand, loam, clay Growth Habit: deciduous; PLANT small shade tree with an attractive, densely branched canopy and brilliant fall color; long-lived and resistant TREES to sea spray and salt; very drought tolerant with low water requirements Flower/Fruit: insignificant green flowers, followed by seed pods on female tree only Size: 30 to feet tall Planting Trees How to Plant a Tree in Houston

Site and tree selection • Choose trees suited to your soil. Generally in Harris County, sandier soil is found north of Buffalo Bayou (or I-10) and soil with more clay is found south. There are variations, though, so evaluate your spe- cific site. Organic content can be added to improve most soils. • Consider the light requirements for your tree, as well as its ability to tolerate poor drainage. Building up a bed before planting assures better drainage. • It is always best to purchase locally grown trees. You will find many large stores sell trees from California, Florida, and elsewhere. Ask where the tree was grown before you make your purchase.

Tree planting tips • The best time to plant in Houston is in the fall or winter months, which gives a tree time to establish roots before the summer heat.

• Dig a hole 2 to 3 times wider than the container, but no deeper than Remove the container the depth of the root ball. and loosen roots, • Center the tree in the planting hole. The tree should be straight with unwrap any circling roots before planting. the branches pointing the direction you want them to grow. Make Stake if necessary sure the hole is not too deep or too shallow. The top of the root ball Make sure drip irrigation is within should be about 1” to 2” above grade. Apply 2-3” layer of mulch the basin formed over roots, but keep it at • Remove tree from the container. Remove any dead or injured roots by the berm. least 2” away from the with sharp pruners. If the roots are growing in a tight circle, loosen Base of trunk should trunk. them up so that they will eventually grow out into the surrounding be 1-2” above ground Create a 4-5” soil berm to soil. Remove a circling root. level. contain water around • Back fill the planting hole, filling in around the roots. Use your foot roots to firmly but gently step around the tree making sure there are no air pockets in the soil. Watering after planting will help to compact the soil and remove excess pore space. • Water well. The first two years your newly planted tree will need regular watering. A rule of thumb is 1 inch of water or 8 to 10 gal-

lons per inch of diameter each week either from rain or irrigation. Backfill with existing Dig no deeper than You can use a screw driver to check that the soil is moist at least 8 soil from the hole, and necessary to set tree tamp down soil as you inches down. 1-2” above ground level. fill the hole to get rid • Avoid fertilizing until the root system is established. Refill hole if too deep. of air pockets around • Build a 4 to 5 inch inch berm around the tree located just outside the the roots. DIG HOLE AT LEAST TWO root zone to help hold the rain or irrigation water. (See illustration) TIMES THE ROOTBALL DIAMETER • Place a 2 to 3 inch inch layer of composted mulch in the bowl around the tree, but make sure it is not touching the trunk of the tree. RESOURCES AND Individuals Websites REFERENCES Mark Brian Lady Bird Johnson Wildflower Center Plant Data Base The following experts Advanced Ecology, Ltd. http://wildflower.org/plants/ Will Fleming were invaluable in the United States Department of Agriculture Forest Service Fleming Landscape Company creation of this list; we http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_ very much appreciate Diana Foss of_contents.htm their time, expertise, and Texas Parks and Wildlife Department thoughtful comments. Texas AgriLife Extension Service Jaime Gonzalez http://aggie-horticulture.tamu.edu/ornamentals/natives/ Katy Prairie Conservancy, Coastal Prairie Partnership Texas Parks and Wildlife Flo Hannah http://www.tpwd.state.tx.us/ Urban Sancturaries Manager, Houston Audubon Barbara Jo L. Harwell Conservation Director, Hermann Park Conservancy Books Doris Heard The Garden Club of Houston, Galveston County Master Gardeners, Texas Master Naturalist Trees of Texas, An Easy Guide to Leaf Identification By Carmine Stahl and Ria McElvaney Brad Hendricks City of Houston Urban Forestry Trees, Shrubs and Woody Vines of the Southwest By Robert A Vines Linda Knowles President, Houston Chapter of the Native Plant Society Texas Trees, A Friendly Guide of Texas By Paul W. Cox and Patty Leslie Chris LaChance The Bayou Planting Guide and Habitat Gardening for Houston Texas AgriLife Extension By Mark Bowen Glenn Laird Trees for Southern Landscapes Harris County Flood Control District By William D. Adams TJ Marks Forest Trees of Texas, How to Know Them Houston Parks and Recreation Department By Texas Forest Service Mickey Merritt Texas Wildscapes, Gardening for Wildlife Texas Forest Service By Noreen Damude and Kelly Conrad Bender Taylor Moore Landscape Architect/Owner, New Nurseries Jack Swayze The Davey Tree Expert Company Photos were generously provided by the Lady Bird Johnson Damon Waitt Wildflower Center. Live Oak landscape photo, Mexican Lady Bird Johnson Wildflower Center Sycamore photos and the Montezuma Bald Cypress Photos were provided by The Garden Club of Houston. Parsley Barry Ward Trees for Houston Hawthorn photos were provided by Pauline Singleton. Texas Persimmon landscape photo was provided by Mickey Merritt, John Watson Texas Forest Service. Harris County Flood Control District Many thanks to The Wortham Foundation, Inc. for aiding us in our drought relief efforts and making this publication possible.

Design: Minor Design HOUSTON

The Garden Club of Houston Hermann Park Conservancy The Houston Parks Board TOUGH Katy Prairie Conservancy Lady Bird Johnson Wildflower Center Memorial Park Conservancy TREES