Eastern gamagrass (Tripsacum dactyloides) is a tall bunchgrass species that ranges from four to eight feet in height. It forms clumps one to four feet across and connected with tough, knotty rhizomes. The plants have roots that extend as far as 20 feet below the surface of the ground, and they are further anchored by corms—short, swollen stems that grow vertically downward.
The solid stems may grow upright or bend sharply near ground level. At their bases, the stems are somewhat flat and purplish.
The flat leaves range from 12 to 30 inches in length and 1/2 to 1-1/4 inches in width. They are tapering with long points and have prominent midribs. Overall, the blades are smooth, but they do become rough at the margins. They form short, open sheaths where they join the stem.
The inflorescence of eastern gamagrass is worthy of note. It has one to four spikelike branches with male and female flowers quite distinct on each branch. The female flowers are closer to the base of the branches and resemble hard beads, 1/4 to 1/2 inch long. The male flowers grow in pairs above the female flowers. The male flowers range in length from 1/4 to 1/3 inch.
As its name suggests, eastern gamagrass is a species of the eastern United States, the eastern two thirds of Kansas being at the western end of its range. It was once a very common species, but now persists only where protected from grazing. It is a species of ungrazed prairies and fertile lowlands.
Eastern gamagrass is rather choosy, requiring deep, moist soils. It is at its best in areas where the annual precipitation is over 35 inches, although it can tolerate annual precipitation levels as low as 25 inches. It is very tolerant of long-term flooding. One thing that eastern gamagrass cannot adapt to, however, is alkaline soils—the pH must be at least 5.5 to permit this species to grow. It prefers full sun, but can survive in partial shade.
Eastern gamagrass is among the earliest of the warm-season grasses to appear. It starts up in mid-April and grows abundantly throughout the spring. However, it will continue growing as late as mid-September thanks to its long roots, which help it resist drought.
This perennial species flowers in June and July. The seeds mature as fall approaches and break off the plant at the joints.
A native species, eastern gamagrass plays an important role in erosion control wherever it grows, but particularly along streams. It also has great benefits for wildlife, offering food, cover, and nesting areas for a variety of species. For example, it is a popular choice for hosting the eggs and pupae of butterflies, and it is the preferred food of the bunchgrass skipper caterpillar. Also, deer and many gamebirds eat the seeds.
During the growing season, eastern gamagrass is extremely nutritious and palatable to all types of livestock. Cattle, in particular, will graze it to death if permitted, so careful management is a must for this species. Eastern gamagrass is hard to establish in the pasture, and should be no-till drilled to avoid weed growth. Dormant seed can be planted between December 1 and March 1, as the winter chilling process will (hopefully) encourage the seed to awaken as temperatures warm. However, this process is far from foolproof, so you might want to purchase stratified seed, which has been chilled, soaked, and treated with fungicide. Stratified seed should be planted between March 15 and May 30, after the soil has reached at least 55°F. Either way, the seed should be planted at a rate of six to eight pounds of pure live seed per acre and drilled 1/2 to 1 inch deep. Rows should be 10 inches apart or less to encourage a dense stand that can compete with weeds. Frequent clipping may be necessary to keep weeds in check before the plants can withstand grazing.
After one to two years, the grass should be established enough to use for pasture. Annual burning is recommended to destroy thatch and fight off weeds. The burning should take place in the spring when the grass is one inch tall; note that this will be much earlier than is typical for other native warm-season grasses. Let the grass grow to a height of 18 to 24 inches before introducing livestock for grazing. Eastern gamagrass responds best to short, intense pulses of grazing pressure, making management-intensive grazing a must. Do not allow livestock to graze the pasture shorter than 8 to 10 inches. Allow each paddock a minimum of 30 days, perhaps even as much as 42 days depending on conditions, to rest before restocking. Remove all livestock from the pasture by September 10 to give the grass enough time to recuperate before winter dormancy. After dormancy, eastern gamagrass loses most of its nutritional value.
Eastern gamagrass makes excellent hay. It will tolerate two cuttings a year. The first should be when the seedhead is developing but has not yet emerged from the top of the plant (the boot stage), when the grass is 24 to 36 inches tall. In Kansas, this will likely occur within a fairly narrow window in mid-June. The second cutting should be planned for six weeks after the first, when three to four collared leaves are present. No matter when you are harvesting eastern gamagrass hay, always leave six to eight inches of stubble. Do not cut this species after September 10.
This grass can make a good lawn if seeded at a rate of one pound for every 200 square feet. However, eastern gamagrass is even more attractive if used in landscaping, where it can be allowed to reach its full height and produce showy inflorescences. It can make a good boundary or screen, but it also adds interest to the garden when planted as a focal point. It is low-maintenance in the garden, but to encourage healthy growth be sure to cut back last season’s leaves before the plant awakens in the spring.
There are no known hazards associated with eastern gamagrass.
This plant is fairly distinctive, particularly after the inflorescence has appeared. It should present no identification problems.
Parts of a Grass Plant: A Glossary
Definitions for technical terms used in this post.