by Chris Hicks, County Director – UT Extension Smith County
Over the past few weeks I have discussed some of the benefits of adding native warm season grasses (NWSG) to a forage system or wildlife habitat. Adding NWSG can give extra forage during the summer and provide quality habitat and cover for several species of wildlife. Establishing NWSG can be difficult, but with the correct planning and execution, you can be successful.
A variety of reasons exist for why people struggle in establishing NWSG. The most common include drilling the seed too deep, inadequate weed control, and planting too late in the growing season. Also, when planting NWSG be sure and consider seed quality. Purity of NWSG seed is often low (50–70 percent) because of an inordinate amount of inert material (stems, leaves, etc.). In addition, the germination rate may only be 50–60 percent. From the seed tag, the percentage of pure live seed (PLS) can be calculated. This figure is then used to determine the bulk-seeding rate. This is a critical step when weighing seed and determining the seeding rate prior to planting.
NWSG do not compete well with non-native grasses, such as tall fescue, bermudagrass, crabgrass and johnsongrass. Control of non-native grasses, as well as many broadleaf competitors, is critical in successfully establishing NWSG. It is particularly important to eradicate perennial competitors before planting. Most often, a glyphosate herbicide (e.g., Roundup, Cornerstone) is used to kill existing cover. When converting a field of perennial cool-season grass to NWSG, the optimum time to spray the existing cover is in the fall before planting the following spring. This is because cool-season grasses are actively growing during October and November, which allows the herbicide to move throughout the plant more effectively.
When wildlife habitat is the objective, many fields of tall fescue can be enhanced without planting NWSG. By simply eradicating the non-native cover and allowing the seedbank to germinate, quality early-successional cover may develop within two growing seasons (depending upon the composition of the seedbank).
Once the competition is controlled, the seedbed should be prepared before planting. If drilling seed, a firm and “clean” seedbed, free of deep thatch and other material, is desired. This will enable the seed to be planted adjacent to mineral soil, which should increase germination success. If the seed is planted in deep thatch, germination and seedling survival may be less than desirable.
Switchgrass and eastern gamagrass tend to have a high dormancy rate. Germination can be improved by treating the seed in a process known as “chilling”. NWSG should be planted mid-April through early June. Later plantings can be successful, but germination and growth may be reduced, as rain is less dependable in June and July.
Seed may be broadcast or drilled, but should not be planted any deeper than ¼ inch. In fact, when drilled, at least one-third of the seed should be obvious on top of the planting furrow. The exception to this rule is eastern gamagrass, which should be planted approximately 1 inch deep. Drilling is usually the preferred method for planting NWSG. A pre-emergence herbicide application at planting is strongly recommended to ensure adequate weed control.
For more information on establishing NWSG, including seeding rates and a list of herbicides available, contact the University of Tennessee Extension office at (615) 735-2900.
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