Indiangrass / Sorghastrum nutans

Indiangrass, along with switch grass and big bluestem, once dominated millions of acres in central North America and is a key tallgrass prairie species.  Like most other prominent tallgrass prairies grasses, Indiangrass is a warm-season grass that photosynthesizes most efficiently during the hottest part of the summer.

Traditional use:

Indiangrass, Sorghastrum nutans, is a perennial bunch grass that provides food and cover for wildlife. Indiangrass isn’t a known medicinal plant, it’s a habitat grass that can grow up to six feet tall. In addition to once having been an important forage grass for bison and elk, Indiangrass seeds are eaten by birds and small mammals. The tall grass can provide small animals with cover from predators, wind or snow. North America’s native peoples wove Indiangrass into baskets and mats and dyed and threaded it with beads, bark and quills for ornament. (Macleod, 2017).

Indiangrass is the state grass of Oklahoma, and the resolution making this designation official declares that Indiangrass “has been in the past, and remains today, one of the most productive, palatable and important native grasses in Oklahoma.”
(Oklahoma State Senate Concurrent Resolution No. 2, Monday, January 24, 1972)
(Photo courtesy of Prairie Moon Nursery)

Indiangrass seedlings

Plant Characteristics:

Indiangrass is a tall, bunching sod-former. The leaves are slender and can grow to 1/2″ wide and 2′ long. Roots can reach a depth of seven feet. The feathery, plume-like golden/bronze/brown colored panicles on top of the vertical flowering stems are the most easily distinguishable feature of Indiangrass. Indiangrass can tolerate an extremely wide range of soil, water and pH conditions. Plants are wind-pollinated and can spread by rhizomes. Indiangrass seedlings can often be outcompeted by faster growing weeds or be killed by atrazine, a commonly used herbicide (Henning, 1993).

Current use:

Like other tallgrass prairie grasses, Indiangrass has a dense web of fibrous roots and so a stand of Indiangrass once established can hold soil particles in place and rapidly absorb water. Indiangrass can grow in almost all types of soil provided there is sufficient depth and has many wildlife friendly attributes. Combined, these traits make Indiangrass an effective potential contributor to many erosion control projects, such as along roadsides and stream banks, and useful for site revegetation / soil restoration work (Poole et al.). Indiangrass seed has become more widely available in recent decades, indicating intentional planting of this Indiangrass is on the rise.

Stuff Almost Nobody Knows:

(for the perpetually curious)

Grass species can be divided into two temperature categories, warm season grasses and cool season grasses. Cool season grasses grow most actively when temperatures are between 60 and 75°F and warm season grasses grow more actively grow most actively when temperatures are between 80 and 95°F. There’s a biological reason for this; warm season grasses and cool season grasses photosynthesize using slightly different chemical pathways (OSU, 2020). In addition to having ideal temperatures for growth 20°F lower than those for warm season grasses, cool season grasses begin growth at cooler temperatures and need more water to grow. Lawn grasses in the US Northeast are generally cool season grasses; when they turn brown and stop growing in August, the problem can be temperature, not just lack of water. Lawn grasses in the US South are generally warm season grasses and southern lawns tend to stop growing and turn brown in the winter even if temperatures remain well above freezing.

Indiangrass is a warm season grass but that doesn’t mean it won’t grow in cooler climates. A North American native plant, Indiangrass has a range that extends from Quebec to Florida. Most locations in North America experience optimum growth temperatures for both cool and warm season grasses for some part of each year. An “all season” grass which grows optimally in all non-freezing temperatures doesn’t exist. If grass is being grown to provide forage, making space for both warm and cool season grasses to grow can be used as a strategy to reduce seasonal variability in overall grass growth rate. The figures below assume a generally northeastern North American climate and illustrate how warm and cool season grass growth rates can be complementary.



“The grass isn’t greener on the other side, it’s greener when growing conditions are optimal for that kind of grass.”



Figures from Poole et al., Vegetating with Native Grasses in Northeastern North America

It is known that the timing of a prescribed burn can be used to systematically advantage or disadvantage certain types of plants. Indiangrass is a fire-tolerant warm season grass. The northeastern North American climate provides relative advantage to cool season grasses. Indiangrass apparent vigor increases as a result of a late spring burning which happens just prior to green-up (USDA FEIS, 2020). In northeastern North America, a late spring low-intensity burn targeting cool season grasses in a mixed-grass planting could serve as a mechanism which would give warm season grasses more of a chance to compete. The details of the precisely how Native Americans used fire for landscape management have been largely lost but it is generally agreed that this was done. Indiangrass is one of the most widespread prairie grasses in North America and this distribution may be partially explained by historical intentional burning norms.


Black Squirrel Farms strives for accuracy but everyone makes mistakes sometimes. We’re happy to update our information if needed. Please contact us if you spot an error or have a suggested edit, update or information inclusion. Help is welcome.


References:

Henning, J. 1993. Big Bluestem, Indiangrass and Switchgrass. https://extension2.missouri.edu/g4673#:~:text=Atrazine%20can%20be%20used%20as,pound%20active%20ingredient%20per%20acre. University of Missouri Extension, Curators of the University of Missouri, Missouri.

Macleod, C. 2017. Sorghastrum nutans. http://nanps.org/native_plants_know/sorghastrum-nutans-indian-grass-4-4/, North American Native Plant Society. Toronto, ON

Oregon State University (OSU), 2020. Differentiate warm-season from cool-season grasses. https://forages.oregonstate.edu/nfgc/eo/onlineforagecurriculum/instructormaterials/availabletopics/grasses/differentiate, Oregon State University, Forage Information System, Department of Crop and Soil Science, Corallis, Oregon.

Poole, B., United States Department of Agriculture (USDA) Natural Resources Conservation Service and Ducks Unlimited, Canada.Vegetating with Native Grasses in Northeastern North America. https://www.dot.ny.gov/divisions/engineering/environmental-analysis/manuals-and-guidance/epm/repository/nypmsbk10321_ocr_0.pdf US Department of Agriculture, Washington, D.C., USA.

United States Department of Agriculture (USDA), 2020. Fire Effects Information System (FEIS) / SPECIES: Sorghastrum nutans, https://www.fs.fed.us/database/feis/plants/graminoid/sornut/all.html#DISTRIBUTION%20AND%20OCCURRENCE, Forest Service, United States