Eastern Gamagrass is a perennial warm season (C4 photosynthesis) grass that can live to be over 50 years old. It has relatively wide leaf blades with a noticeable white central vein; this feature causes it to be mistaken for an introduced invasive grass, Johnsongrass. Eastern Gamagrass is a distant relative to corn and the male flower parts resemble a corn plant’s tassel. The female flower part is directly below the male florets, and the flower spikes resemble fingers, which is the meaning of the dactyloides in the Latin name, Tripsacum dactyloides. The seeds that form on the flower spikes resemble a stack of pencil erasers in shape and size. The seeds need to undergo cold, moist stratification to germinate and are often planted 1-2″ deep. Perhaps more impressive than the above-ground portion of the plant is the root system, which is extensive and deep. Much research about the plant’s root system was reported by Clark et al. in a 1998 Plant and Soil journal article, “Eastern Gamagrass Root Penetration into and Chemical Properties of Claypan Soils.” The roots commonly extend deeper than a man is tall, even growing through dense soil layers that are impenetrable to many plant roots such as clay pans, which allows them to access water and nutrients that most plants cannot. Despite their length, the life of the roots is less than 2 years meaning that the plant is always replacing old roots. However, old root channels provide easy avenues for the growth of new roots or even other plant species’ roots. Eastern Gamagrass roots have a unique ability to withstand waterlogged soils; air passages within the roots, called aerenchyma, allow the plant to transport air from above ground into its roots. The plant uses this oxygen for its own needs, but it may also use it to ameliorate unfavorable soil conditions such as the oxidation of toxic manganese to nontoxic forms. Furthermore, this plant’s roots show good tolerance to soil acidity and aluminum toxicity. Eastern Gamagrass roots can also be colonized by arbuscular mycorrhizae; association with this group of fungi commonly benefits plants by improving plant establishment and acquiring water and nutrients, especially phosphorus, for the plant. Associative nitrogen fixation, in which bacteria give the plant nitrogen in exchange for food, was reported by other researchers, Brejda et al., in the Journal of Range Management article, “Indications of Associative Nitrogen Fixation in Eastern Gamagrass”. .
The nutritious leaves of Eastern Gamagrass are readily eaten by large herbivores, and were likely an important food source for bison and elk. The large stature of the plant lends itself to providing protective cover for various wildlife species. The golden byssus butterfly caterpillar uses Eastern Gamagrass as a food source as do an assortment of other insects.
Icecream Grass is a common nickname for Eastern Gamagrass due to the fact that it is highly palatable and nutritious as well as being quite productive. It is commonly grazed and hayed and is also used as an alternative to annual silage crops. Data from the Plant Materials Center at Elsberry, MO indicate that the crude protein level of regrowth Eastern Gamagrass is above 11% and often 12-13% throughout the growing season with early spring levels measuring around 18%. This grass has little stem in comparison to other grasses and has very consistent forage production during the growing season. In comparison to the introduced forage species, Caucasian Bluestem and Bermudagrass, Eastern Gamagrass does not dip in production during the dry periods of the summer. Eastern Gamagrass greens up early in the spring compared to some other warm season grasses, which is desirable on one hand, but in a cool season dominated grazing system, it overlaps with the growth curve of the cool seasons creating a need to be everywhere at one time. This grass does not appreciate continuous grazing; rest periods of ~45 days are needed to maintain a balance between stand vigor, forage yield and forage quality. Also, a 45 day rest period prior to a killing frost is desirable.
Being a large grass, Eastern Gamagrass is not commonly thought of as a landscaping plant. However, it can be used as a large accent plant or as a substitute for a low shrub. It is a natural choice for moist areas. The rich green leaves often give the plant a spiky look. In the fall, the leaves turn to a pretty red-bronze color. In most situations, the plant is long-lived and does not spread aggressively.
This species is naturally found in bottomland forests as well creek and river bottoms that are shady or full sun. River Oats grows beneath a fairly heavy canopy of trees, but it will also grow in full sun when the soils are moist. River Oats is found on drier sites when there is more shade.