Ask Mr. Smarty Plants

Mr. Smarty Plants was recently asked a similar question, and rather than repeat the information, would like for you to read that previous answer.

All plants have some sort of defense mechanism to assure they get their own space and can have all the nutrients they want from the soil. Members of the Carya genus, which includes pecans, hickories and walnuts, emit chemicals called juglones, which can damage or kill plant material beneath the tree. Plants that chemically protect themselves are referred to as allelopathic. Usually they don't begin to show these tendencies until the plant in question has reached a certain level of maturity, and needs more nutrients and water from the soil. Although the pecan has a taproot, it still has roots 6 to 12 inches from the surface of the soil, probably extending far beyond the dripline of the tree. Combined with the shade of a mature pecan tree, the grass beneath your tree simply had to go, as far as the tree was concerned. 

However, as you'll note from the previous answer we referred you to, there are grasses that can survive in shade and seem to be somewhat resistant to the tree's chemical warfare.  You didn't say what grass you had under the tree originally, but we would urge the use of grasses native to your area. At the Lady Bird Johnson Wildflower Center, we support the use and propagation of plants native not only to North America but also to the area in which the plant is being grown. Most of the commonly used turf grasses, including Bermudagrass and St. Augustine, are non-native. A native plant will have a better chance of survival because it has already evolved to be tolerant of the soil, climate and moisture where it is being grown. 

To find grasses that should work in your area, we went to our Recommended Species section, and clicked on "Texas High Plains" on the map.  We then went to NARROW YOUR SEARCH and specified "grasses" under Habit, and part shade (2 to 6 hours of sun daily) under Light Requirements. This gave us a list of 7 grasses that are recommended as doing well in the Abilene area, from which we selected 4. We also checked out the 4 grass selections in the previous answer, and found they are also possibilities for your area, with some notes on their needs. 

Follow the plant links to our website on each grass, and read what their expected heights are, whether they are cool-season or warm-season grasses and how to propagate them. None of these are what you would call a turf grass, but they are attractive, hold their places year round, and serve as nesting areas and food sources for birds. When you have made some choices, go to our Native Plant Suppliers section, type in your town and state in the "Enter Search Location" box and you will get lists of native plant nurseries, seed companies and landscape consultants in your general area. In particular, we would suggest Native American Seed in Junction, TX, which has an extensive grass selection in their online catalog with more information, and they provide mail order.

Bouteloua curtipendula (sideoats grama)

Pascopyrum smithii (western wheatgrass)

Poa arachnifera (Texas bluegrass)

Sorghastrum nutans (Indiangrass)

Chasmanthium latifolium (Inland sea oats) - tends to prefer more acidic soil than you are likely to have in the Abilene area, but seem to be pretty adaptable, worth a try

Elymus canadensis (Canada wildrye) - also prefers slightly acidic soils

Muhlenbergia schreberi (nimblewill) - needs moisture

Carex blanda (eastern woodland sedge) - also needs moisture

Bouteloua curtipendula

Pascopyrum smithii

Poa arachnifera

Sorghastrum nutans

Chasmanthium latifolium

Elymus canadensis

Muhlenbergia schreberi

Carex blanda