Boerne Chapter

Acacias are NICE! in this part of the Hill Country

Author: Bill Ward

Texas has a large number of Acacia, as many as 17 or 18 species and varieties, according to which taxonomist is making the list. Some members of that genus are excellent small trees and shrubs for landscaping in this area. As our water supply in the Hill Country continues to diminish, we ought to think more about acacias as yard plants.

Acacias are some of the most drought-tolerant bushes and trees one can grow. Once established, they need no water except what Mother Nature provides. Even during this historically severe drought, the acacias seem to be surviving just fine. Several species of Acacia fit the bill as an Operation NICE! (Natives Instead of the Common Exotics!) Plant of the Month. They look good in the yard but require little or no water, fertilizer, and other care.

Tree full of yellow blooms
Huisache in bloom.

The acacia probably best known to Central and South Texans is huisache (Acacia farnesiana or A. smallii), also known as sweet acacia. This spiny acacia has feathery doubly compound leaves with 10-18 pairs of tiny secondary leaflets. Usually it gets no more than about 15-20 feet high in this area. During early spring, the branches are densely packed with half-inch spheres of bright-golden-yellow blossoms.

Some of the prettiest early-spring sights in northeastern Mexico are broad valleys covered in huisache trees. On February mornings, the whole landscape glows golden yellow as far as the eye can see.

Reportedly, “huisache” comes from an Aztec word, huitz-axin. “Huitz” means it, he, or she comes, and “axin” is a yellow oily substance derived from a bug and used to stain skin and other things yellow. Perhaps, then, huitz-axin refers to this acacia becoming yellow in the spring. That’s merely a guess.

Huisache may not always be available in nurseries, because some people consider it a trash tree. In South Texas it rapidly infests disturbed land and is consider a nuisance by many ranchers. However, on the eastern Edwards Plateau it seems much less likely to spread out of control. We’ve had two small huisache trees in our yard for years. They grow slowly and have not multiplied.

Our most common local acacia is Roemer’s acacia (A. roemeriana), sometimes called catclaw. This multi-branched shrub or small tree has doubly compound leaves with 4-8 pairs of leaflets. In late spring it puts on round, fluffy clusters of white flowers. The curved catclaw-like thorns will get your attention if you brush against this shrub.

Tree full of light green foliage
Huisache tree in bloom.

Another species of catclaw acacia (A. greggii var. greggii and var. wrightii) grows in the South Texas brush country, Trans-Pecos, and part of northwest Texas. This acacia can grow to 25 or 30 feet high. It has twice-compound leaves 1-2 inches long. Leaflets number 2-6 pairs. Instead of the bloom head being spherical as in Roemer’s acacia, flowers are cylindrical spikes of many tiny white flowers. This is the most-cold-hardy acacia native to Texas and probably can be used effectively in landscapes in northern Texas (Sally Wasowski, “Native Texas Plants, Landscaping Region by Region”).

Another acacia shrub that does well in our yard is guajillo (A. berlandieri), native to South Texas and the southern edge of the Edwards Plateau. This acacia has airy compound leaves with 5-9 pairs of primary leaflets and 30-50 pairs of secondary leaflets. In South Texas it produces white ball-shaped flower heads from November to March. In our yard it blooms in the spring, and its white flowers are a nice complement to the bright-yellow rounded bloom heads of a nearby goldenball leadtree.

There also exists a Texas acacia which can be used as a groundcover. Fern acacia (A. angustissima) is a low-growing shrub with delicate, fern-like foliage. Its leaflets close together at night and when touched. Unlike most other acacias, fern acacia is thornless. White round flowers appear from time to time during the summer and fall. It is hardy in full sun or partial shade, and it never needs watering. Fern acacia fits into the unkempt wildscape of our backyard, but it spreads by rhizomes and might be too unruly for many gardens.

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About the Region

New Braunfels, the location of our Fall 2024 Symposium, straddles both the Edwards Plateau Ecoregion and the Blackland Prairie ecoregion. Interstate 35 divides the city of New Braunfels; its path through the city closely parallels the boundary of these two ecoregions, with the Edwards Plateau on the west side and the Blackland Prairies region to the east. The Edwards Plateau area is also called the Hill Country; however, this general term covers a much larger area extending farther north. Spring-fed creeks are found throughout the region; deep limestone canyons, rivers, and lakes (reservoirs) are common. Ashe juniper is perhaps the most common woody species found throughout the region. Additional woody species include various species of oak, with live oak (Quercus fusiformis) being the most common. Sycamores (Platanus occidentalis) and bald cypress (Taxodium distichum) border waterways. This area is well known for its spring wildflower displays, though they may be viewed in spring, late summer, and fall, as well. According to Texas Parks and Wildlife, average annual rainfall in the Edwards Plateau ranges from 15 to 34 inches.

The Blackland Prairie extends from the Red River south to San Antonio, bordered on the west by the Edwards Plateau and the Cross Timbers, and on the east by the Post Oak Savannah. Annual rainfall averages 30 to 40 inches, with higher averages to the east. This region is dominated by prairie species. The most common grass species include little bluestem (Schizachyrium scoparium) and Indian grass (Sorghastrum nutans) in the uplands and switchgrass (Panicum virgatum) in the riparian areas and drainages. Common herbaceous flowering plants include salvias, penstemons, and silphiums. This area has suffered greatly from overgrazing and agricultural use. Few intact areas remain, though many of the plants can be found along county roadsides throughout the region.

Our four host chapters (New Braunfels, Lindheimer, Guadalupe, and the Hill Country chapters) are located in one or both of the ecoregions above. However, the eastern portion of Guadalupe County also falls within the Post Oak Savanna ecoregion. Annual rainfall averages 35 to 45 inches, with higher averages to the east. A wide variety of hardwood trees are found, including several species of oaks, elms, and in the Bastrop area, loblolly pine (Pinus taeda). Grasses and forbs dominate in the open savannas, with most common grass being little bluestem. Ranching, agriculture, and fire suppression have allowed woody species to encroach on the once-open savannas.

Source: Wildflowers of Texas by Michael Eason