Black Walnut Tree

Black Walnut Tree

Unique Trees of North Texas:

Black Walnut

(Juglans nigra)

By Jeremy Priest

The next tree in our unique tree series is native from South Dakota to Florida and follows the eastern edge of the Cross Timber region to Central Texas. Black walnut (Juglans nigra) has been a prized tree for historic farmland and ranches. This is due in part to valuable walnuts and characteristic heartwood of the tree, but also for it’s indication of soil quality. Black walnut is typically found on deep, rich soils and the wood of this tree is hardy and has beautiful, highly valued grain. The large walnuts produced by this species are difficult to extract, but highly rewarding.

Black walnut full leaf and walnut fruit

Black walnut leaf and fruit

Black walnut is most likely be confused with pecan as it is in the same family and may occur in similar sites. It’s plantation usage was not nearly as popular as pecan in North Texas, but individuals can sometimes be found near old pecan plantations. Black walnut can be distinguished as it contains more leaflets than pecan and the leaf is larger: 12-24 inches long. Chinese pistache has similar leaves, although the leaflets on pistache have smooth margins while black walnut typically has fine serration. This species is most quickly identified by it’s fruit. Walnuts appear dark brown and furrowed after the outer layer is removed, but are covered by a thick, green husk with almost sandpaper like texture when they are immature on the tree. As the fruit matures, the outer husk changes color to nearly black and the husk is absorbed into surrounding soil. Black walnut is an allelopath, which means that it produces chemicals toxic to most other plants. This natural herbicide is concentrated in the husk surrounding the walnut and helps reduce competition for the young seedling. The toxin is not strong enough to harm most trees, but could impact sensitive garden plants and some conifers, especially under a fully mature tree. For more information on juglone toxicity click here.

As evidenced by the naturally allelopathic seeds, black walnut needs full sun when young, and the tree also requires adequate water in well-drained soil. Although the native black walnut prefers a lower pH than typically found in the cross timbers (< 7.5), Texas A&M produces a Texas variety of little walnut (Juglans microcarpa) which is better suited to high pH soils. Black walnut can be somewhat slow growing, except when planted in ideal conditions. Black walnut is similar to post oak in that it produces deep roots and is not easily transplanted; however, the demand for black walnut seedlings is high enough that nurseries do produce seedlings available to the public, mostly in bare root form.

The state champion black walnut in Bowie County (Northeast Texas) is 56 inches in diameter and 80 feet tall with 177 feet of spread. Extremely large black walnut are possible in North Central Texas as one Dallas County specimen is 65 feet tall with a 69 foot spread. However, most individuals could be expected to reach 40 feet in height and 30-45 feet in width. Trees mature quickly and nut production can begin as early as 6 years, although large crops are not likely until trees are around 20 years old.

Citizen Foresters Plant Trees in Arlington

Citizen Foresters Plant Trees in Arlington

Citizen Foresters help with tree planting - Meadowmere Park

Citizen Foresters and Master Gardeners plant 16 trees in Arlington

The morning of Friday, December 15, 2017, three Citizen Foresters and several other volunteers from the Master Gardeners program planted 16 trees in Arlington. The species planted were cedar elm, bur oak, bald cypress, desert willow, and Mexican plum. Although the morning began with chilly weather, volunteers worked tirelessly, and soon the sun rose over the treetops onto four trees that had already been planted. Thanks to the efforts of the volunteers and the forestry staff, all 16 trees were planted by 10 a.m. The event was coordinated between the City of Arlington, Citizen Foresters, and Master Gardeners with the help of local resident Juliet Bran.

A City of Arlington employee provides a naturally fun smile during the tree planting event

The Parks and Recreation Department’s Forestry and Beautification staff assisted with the planting.

The trees were planted on the median of Shorewood Drive near Bowman Springs Park in Arlington. This street had only a few existing post oak and cedar elm, but will now be able to grow to provide a full tree canopy and beautify this residential street.

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

Citizen Foresters Plant Trees at Lake Grapevine

Citizen Foresters Plant Trees at Lake Grapevine

Citizen Foresters help with tree planting - Meadowmere Park

Citizen Foresters Melissa Carr (Denton), Karen Rice (Grapevine), and Bill Sargeant (Fort Worth) at the Meadowmere Tree Planting

On Saturday, November 12, 2017, three Citizen Foresters joined 27 other volunteers to plant 15 trees (sycamore, red oak, pecan, and dogwood) at the entrance area of Meadowmere Park, on Lake Grapevine.  This Grapevine Arbor Day event was hosted by Keep Grapevine Beautiful, a City of Grapevine agency.  High school and college students, along with parents, formed most of the participants. The weather on this cool and misty fall day was perfect for tree planting.

Volunteers use pickaxes to finish digging the last tree hole at Meadowmere Park.

Volunteers compete to finish digging the last tree hole.

The event culminated in the digging of a hole for planting the last tree: a sycamore. It was a friendly competition between girls and guys: the guys swinging a pick axe and girls handling shovels, both sweating it out to complete a two-foot-deep hole in the hard-caked soil (or perhaps it was rock?). By the time it was completed, both sides agreed it could not have been done without the team effort.