Post Oak in the Cross Timbers

Post Oak in the Cross Timbers

The Post Oak’s “Roll” in the Cross Timbers Region

By Melinda Adams The post oak got its name from early settlers who commonly used the decay resistant wood for fence posts. Post oak takes several forms though out its range but the tree we are most familiar with is an upright majestic shade tree. Its twisted and knarled branches make it one of the most prominent deciduous trees in the winter landscape. Post oak leaves are five lobed and somewhat resemble a crucifix. They are among the last trees to leaf out in the spring and one of the earliest to stop growing, which contribute to their slow growth rate. The average post oak takes more than ten years to grow 2” in trunk diameter. However, it becomes a dominant species on poor sites due to its drought resistance. The cross timbers consisted of upland forests of drought resistant, slow growing trees, that cut through sections of the prairie from Central Texas, Oklahoma and into southern Kansas. Fort Worth is flanked with the Eastern and the Western Cross Timbers. The drought resistant post oak is a dominant species in both, but in the more arid sandier Western Cross Timbers they are closer together, smaller and slower growing. Reportedly, the post oak will not begin to bear acorns until it is about 25 years old. Though acorn production is sparser than other oaks, they are more important to wildlife because they are higher in fatty acids. The University of Arkansas Tree-Ring Laboratory has been conducting research in the Cross Timbers for over thirty years. They have found thousands of post oaks between 200 and 400 years old in all three states. The oldest are usually found on sandy soils or on steep rocky terrain. The height of the post oak is rarely over 100’, or greater than 48” in diameter and the largest recorded post oak is 117’ tall and 52” in diameter. However, in its extreme southern range it often takes the form of a small tree seldom taller than 40 feet. The oldest post oak ever documented in the cross timbers is over 400 years old, but is only 20 feet tall.

A large post oak tree

Post Oak

The gently rolling native grasses of the Fort Worth Prairie once stood between the two Cross Timbers. Settlers wrote of stark transitions from the prairies to the forests, describing them as “walls of woods”. Post oaks invaded the Fort Worth Prairie about the same time we did. Through the suppression of fire, agriculture, and ranching, the abrupt transition has been blurred by an invasion of woody species into the grassland. Many groups of post oaks and black jack oaks grow in Fort Worth where there was once only prairie or savanna. As the oaks matured, their canopies closed and they shaded out the native grasses reducing the fire fuel load. Post oak may have been well suited to survive the rigors of the Cross Timbers or an effective opportunist at invading the prairie. However, it has not faired as well in modern urban developments. Post oak cannot tolerate root disturbance. The tree grows so slowly it is unable to heal torn and ripped roots before they decay. Many post oaks die in patches without apparent cause. Dr. Dave Appel, Associate Professor of Plant Pathology and Microbiology at Texas A&M University, has conducted some interesting studies on post oak decline. He discovered that much had to do with the depth to hardpan. Hardpan is an underground impermeable layer that is associated with water table depth. Since Cross Timbers post oaks grow under arid conditions in well-drained soils, trees over shallower hardpans have water that is more available during prolonged droughts. Trees less than a few hundred feet away that have a deeper hardpan may not be able to survive. Dr. Appel also found just the opposite was true in urban areas. Post oak is one of the least tolerant species to flooding. Post oaks over shallower hardpans will be more susceptible to over watering than those over deeper hardpans. A new water loving homeowner, a new irrigation system, or a recent change in drainage patterns can be enough to tip the scale. Post oak death due to over watering will have similar symptoms of trees with other types of root damage. Tips of branches will die back causing an abundance of epical sprouting (sprouting of small twigs along trunk and/or major limbs). Trees with root damage often take several years to die. As the tree consumes its starch reserve, it will produce fewer and smaller leafs while branches will continue to die back. As the tree uses up the last of its energy reserve, death can appear to happen suddenly after a flush of growth in the spring or acorn production in the fall.

Post oak trees in a park

Post oaks provide shade and a view of the past

You are fortunate indeed if you have a post oak in your yard. Because of their slow growth rate and their difficulty surviving transplanting you will never find one at a nursery. Your tree successfully took hold in the arid grassland or cross timbers and grew slowly and steadily. It was one of the lucky few that survived construction and it provides an abundance of shade for you and food for urban wildlife. If you are lucky enough to have a post oak under your care, like a cactus, it will be healthier if you simply ignore it. Don’t over prune it or feed it, and avoid putting flowerbeds or driveways under the canopy where you will disturb its roots. Just enjoy its beauty and its shade. When your neighbor’s exotic imported trees are wilting in the hot Texas sun, you’ll be as happy as your post oak with your reduced water and electric bill.

Texas Persimmon Tree

Texas Persimmon Tree

Unique Trees of North Texas:


Texas Persimmon


(Diospyros texana)

Texas persimmon in winter

Texas persimmon in winter

By David Coke and Gene Gehring

The Texas persimmon (aka Mexican persimmon, black persimmon, or Chapote Negro) is not to be confused with common persimmon (Diospyros virginiana) which has larger fruit, a single stem, and is taller with rougher bark. Texas persimmon looks more like crapemyrtle when older, and is usually multi-stemmed with smooth bark.


This tree’s range is primarily in the southern half of Texas and into Mexico, particularly southwest of the Colorado River. Its native range does not extend into the upper Gulf Coast, north Texas, or far west Texas. It likes dry, rocky areas and doesn’t like “wet feet”. Planting in a yard that gets regular watering can make for an unhappy Texas Persimmon; however, this native understory tree is able to withstand some shading from larger canopy trees. Texas persimmon has been successfully planted in North Texas and can live 30 to 50 years when conditions are right.


It can grow to 35 ft, but is typically about 10 ft high. It has a rounded crown and a smooth, gray bark. As the tree ages, the bark will start to peel away from the trunk and reveal lighter colors underneath. It is a deciduous tree but can be evergreen in its southern areas. It has 1” to 2” oval to oblong leaves which are leathery, fuzzy underneath, and curled over on the edges. They are dioecious (separate male and female plants) and since the species is not common in the area, both sexes would need to be planted to produce fruit. They flower starting in March or April and have small white flowers. That is followed by a small, black fruit which is about ¾” and is edible when ripe. It has lots of little seeds though making that difficult. The fruit it typically ripe in August. It is also used to make a black hair dye or dying leather. Be careful, it can stain the skin black as well. The fruit is enjoyed by a wide range of birds and mammals. Its tough, dark heart wood was used for tool handles.


The national and state champion Texas persimmon tree is located in Ulvalde County. That individual is 26 ft tall, has a 22 in diameter, and shades an area 31 ft across.

Selecting the Right Tree

Selecting the Right Tree

Remember to consider soil and surroundings when choosing your next tree

By Jeremy Priest

Most of us know about proper tree planting procedures (if not, see the resources below), but did you know that one of the most important aspects of a tree’s success starts with selecting the right tree? Many times a homeowner will plant a tree without considering two very important aspects: soil type and growing space. The first step in tree planting should be evaluating your soil conditions to determine some basic aspects.

  • Soil pH: The cross timbers region has a range of pH from acidic to alkaline so it’s important to choose species fitting your soil. The more eastern species such as redbud, maples, southern pines, and red oaks are examples of species that generally prefer acidic soils.

    Red oak located under power lines on a poor soil type

    This red oak is an example of a poor species & location match. The soil at this site is alkaline, which is not ideal for the species. The combination of soil and stress from regular pruning, due to the power lines overhead, lead to the tree’s decline.

    Mesquite, Gambel oak, and Monterrey oak are species that generally prefer alkaline soils. Many popular tree species promoted nationally are not adapted to moderately alkaline soils found in the cross timbers.

  • Soil water and drainage: Coarse texture soils such as sand and silt do not retain much moisture, so upland sites with these soils often have drought tolerant species such as post oak or blackjack oak. If you have this type of soil, and cannot regularly water, consider planting drought tolerant species such as desert willow or live oak. Fine texture soils like clay can retain water to the point of harming the tree. Species adapted to poorly drained soils include eastern redcedar, cedar elm, baldcypress, and bur oak.

Remember to consider pH, water availability, and drainage all together. The next step is to determine how much space is available and what the purpose of the tree will be.

  • Small/ornamental: These trees mostly provide beauty or natural screening from surroundings. Crapemyrtle, desert willow, and Eve’s necklace are examples of ornamental trees.
  • Medium-size: These trees are generally narrow, may not grow as tall as canopy species, and often retain lower branches suitable for providing natural screening. Examples include magnolia, eastern redcedar, or exoctic pines such as Afghan pine.
  • Large/canopy: These species are the dominant trees on the landscape, providing shade and most of the environmental benefits provided by urban trees. Examples include the oak species (live, bur, chinkapin, or post), pecan, native pines, elms, and ash. These trees have a large canopy spread and often provide food for wildlife.

Each size of tree can provide a mix of beauty, screening/visibility, or shade. Consider planting a mix of not only different species, but tree sizes as well. There are lots of resources available on the web to educate and make for a successful tree planting.


Additional Information

A number of sites provide useful information for tree selection; see the list below for help with selecting a tree and learning more about your soil type. This is not a comprehensive list, there are many recommended tree species lists for North Texas out there so please research other sites as well.

Tree Selection Guide – Provided by the Texas A&M Forest Service

U.S. Soil Map – Web Soil Survey from the USDA NRCS

Fort Worth Recommended Tree List – The City of Fort Worth Native & Adapted Tree List

Urban Forest Information Sheets – Helpful information provided by the Texas A&M Forest Service

Tree Planting and Care – How to plant a tree from the City of Arlington

Anacacho Orchid Tree

Anacacho Orchid Tree

Unique Trees of North Texas:  Anacacho Orchid Tree (Bauhinia lunarioides)

The Anacacho Orchid Tree is a unique tree not seen often in the North Texas area. It is a small tree in the Fabaceae family which grows to approximately 15 feet tall. It is reportedly native to only a few canyons in western central Texas and in adjacent northeastern Mexico. It generally grows in a bush form but can be trained into a single-trunk tree. The leaves are bi-lobed almost like a small split Red Bud leaf or a cow hoof shape. The one pictured blooms bright white clusters of flowers in the spring and then forms flattened seed pods much like a Red Bud tree. There is also a Mexican Bauhinia that blooms light pink clusters of flowers.

The Anacacho Orchid Tree can grow in full sun or as an understory specimen. It is very drought tolerant, requires good drainage, and will tolerate different soil types other than the typical limestone soils of where it is native. North of Austin it will freeze during heavy winters but since it grows so rapidly it forms a new tree in less than a growing season.

If you might like to try growing an Anacacho Orchid Tree it is best that it be planted on the south side of your home or where it is shielded from the north and west winter weather.