The native, perennial, warm-season grasses have the potential to produce good hay and pasture growth during the warm and dry mid-summer months. These grasses initiate growth in late April or early May and produce 65%–75% of their growth from mid-June to mid-August in Ohio. Warm-season grasses complement cool-season grasses by providing forage when the cool-season grasses are less productive. Warm-season grasses produce well on soils with low moisture holding capacity, low pH, and low phosphorous levels. However, they do even better on deep, fertile, well-drained soils with good water-holding capacity. They generally require much lower levels of nitrogen fertilization than cool-season grasses.
The following species are winter-hardy and grow in all areas of Ohio. They can be seeded alone or as a mixture, but seeding a single warm-season grass species is easier to manage. Legumes or cool-season grasses generally are not suited for planting with warm-season grasses because they compete too much during stand establishment. Even in established mixed stands, coolseason species may compete too much because they begin spring growth much earlier and suppress growth of the warm-season species.
SWITCHGRASS (Panicum virgatum L.) is a tall, rhizomatous perennial that grows 3 to 5 feet tall. It appears bunch like, but the short rhizomes may produce a coarse sod under grazing. Later in the season, leafy regrowth develops from basal tillers and shoots emerging along the lower stems at leaf nodes. Switchgrass tolerates poorly drained soils, occasional flooding, and perched water tables better than other warm-season grasses. Leaves and stems of switchgrass have good forage value and are readily grazed by livestock in the immature stage; however, it is considered to have lower forage nutritive value than big bluestem or indiangrass. Palatability and nutrient content of switchgrass stems decline rapidly after heading. Switchgrass is often the choice among farmers trying a warm-season grass for the first time. The seed is clean, free flowing and can be seeded with standard forage seeding equipment.
BIG BLUESTEM (Andropogon geradii Vitman) is an erect, robust, perennial bunchgrass that grows 3 to 6 feet tall and is often reddish-purple at maturity. It produces foliage in late spring from buds at basal nodes and from short, scaly rhizomes. Growing points stay close to the ground until late summer when heads appear. It is considered more palatable than switchgrass or indiangrass, especially after maturity. Big bluestem is more drought tolerant than other warm-season grasses and better adapted to excessively drained soils with low water-holding capacity. The seed is light, chaffy and difficult to seed without a special grassland drill.
INDIANGRASS (Sorghastrum nutans (L.) Nash) is an erect, robust perennial growing 3 to 6 feet tall. It has short, knobby rhizomes and spreads slowly. Indiangrass starts growth somewhat later than switchgrass or big bluestem and provides good quality forage during much of the summer. It is moderately palatable after heading. Indiangrass can be planted on moderately well-drained soils and can withstand occasional flooding. The seed is light, chaffy, and difficult to seed without a special grassland drill.
EASTERN GAMAGRASS (Tripsacum dactyloides (L.) L.) is a robust, upright, leafy bunchgrass that grows 6 to 12 feet tall. It is adapted to deep soils with good waterholding capacity. In natural habitats, it grows in fertile bottomland, swamps and along streambanks. Eastern gamagrass is one of the earliest warm-season grasses to begin growth in the spring. It has high-yield potential and maintains its quality better when mature that the other species. One drawback to eastern gamagrass is its need for a long, late summer rest period beginning by mid-August.
Establishment
Soil pH should be at least 6.0, and phosphorus and potassium should be applied based on soil-test recommendations. Do not apply nitrogen fertilizer at seeding, which will only stimulate excessive weed competition. About 30 pounds per acre of nitrogen can be applied on low fertility sites in July after the grasses have started growing provided the stand is very good and weed competition is not high.
The perennial warm-season grasses are slow to establish and are weak competitors with weeds until established. Attempts to establish warm-season grasses under heavy weed infestations often fail completely or will at best require two to three years before acceptable growth is achieved. Fields previously in row crops where weeds were controlled are ideal sites. Two years is generally required for successful establishment of warm-season grasses. Plateau herbicide (ammonium salt of imazapic) can be used to control weeds during establishment of big bluestem and indiangrass, as well as established stands of those species. Consult the herbicide label for further details.
Spring seedings should be made from mid-April to mid-May, the earlier dates being especially better for southern Ohio. Use the seeding rates listed in Table 7.4. Switchgrass and eastern gamagrass can be planted with standard drills equipped to handle cool-season grasses, but big bluestem and indiangrass require special grassland drills unless the seed is debearded. These grasses can be seeded in conventionally tilled seedbeds or no-tilled where existing competition is eliminated. Seed should be planted ¼ to ½ inch deep, except eastern gamagrass which has a larger seed and should be planted ½ to 1 inch deep. Seed stratification requirements of eastern gamagrass need to be followed closely to assist in germination of this species.
A seeding year stand of warm-season grass should not be harvested unless growth is unusually vigorous and the stand is strong. Weed competition in the seeding year can be reduced by clipping weeds above the warmseason grass seedlings. Adjust the clipping height upward as the season progresses to prevent clipping off the warm-season grass seedlings, as that would reduce their vigor. Do not clip or graze new seedlings after Aug. 1. It is usually best not to graze warm-season grasses during the seeding year.
Managing Established Stands
Perennial warm-season grasses are more tolerant of low pH and fertility than the cool-season species, but they will respond to higher levels of fertility. Soil testing at least every three years is the best guide for maintenance rates of phosphorus and potassium. The timing of phosphorus and potassium application is not critical, and rates are similar as those for cool-season grasses. Lower nitrogen rates are suggested for warmseason grasses than for cool-season grasses. If a single application is made, 60 to 80 pounds of nitrogen per acre can be applied in mid- to late May. For higher rates, split the application with half in mid-May and half in early July. Higher rates should be used only on highly managed excellent stands.
Harvest or graze these grasses when they are 16 to 20 inches or more in height (boot stage). Once seedheads emerge, the quality decreases rapidly. Heading will occur in late June to early July, depending on location, year, and species. Leave at least a 5-inch stubble for rapid regrowth. Mowing or grazing closer than 5 inches will remove important plant carbohydrate storage organs and areas of new bud development. Rotational grazing is advised for good persistence. Enough time should be allowed for at least 12 inches of fall regrowth before frost on all species, so do not graze or harvest after mid-September. Plants can be harvested after a killing frost without damage to the stand and the forage is safe for livestock. Removal of dead stubble in December will increase grass yields during the following growing season. This can be done with grazing animals, but these animals will need protein supplementation to balance protein needs. Leave at least an 8-inch stubble cover for the winter.