Big bluestem (Andropogon gerardii) is one of the most iconic plants of the tallgrass prairie. Its sturdy, upright stems are usually covered with a blue, waxy coating, giving it its name. These stems grow in clumps and vary dramatically in height depending on the environment. Big bluestem can be a modest three feet tall, but it can also reach an amazing nine feet in height. The scale of the stems pale in comparison to the root system, however, which may probe as deep as 13 feet below the surface of the ground!
The leaves of big bluestem also tend to be somewhat bluish in the summer, although they turn a rich copper color in the fall. The blades may be flat or rolled either inward or outward and vary from 1/4 to 1/2 inch in width. Their length is even more variable, ranging between six and 24 inches. The blades usually feel smooth on the underside and rough on the margins and upper surface due to fine hairs.
Close observation will reveal several characteristics about the leaf sheath that can aid in identification. The sheath itself appears slightly flattened and is typically covered in fine, silky hairs. There is often a coating of hair near the collar where the sheath and blade join, as well. Inside the blade at the sheath, note the small membrane that forms the ligule, a protective feature to keep water from running into the sheath.
Another common name for big bluestem is “turkey foot.” This comes from the appearance of the inflorescence, which resembles the three forward-pointing toes of a turkey. But do not be confused if the inflorescence contains more than three “toes” or racemes—some plants may bear seven! Each raceme may be 1-1/2 to 4 inches long and is purplish to brownish in color.
Big bluestem produces both seeds and rhizomes. The former have awns, which give them a hairy appearance. In fact, the scientific name Andropogon comes from the Greek words andro “man” and pogon “beard.” The rhizomes are very shallow, reaching no more than two inches into the ground.
Big bluestem is an important native grass in every state and province east of the Rocky Mountains. It is found across Kansas, although it becomes more scarce on the shortgrass prairie of the southwest corner. It favors open, sunny sites of all varieties, ranging from wide-open plains to woodland meadows to roadsides.
This species can adapt to most well-drained soils. However, it cannot tolerate saline or excessively alkaline soils. While its pH preference is around neutral, big bluestem can handle a pH as low as 4.0.
Big bluestem is best adapted to USDA plant hardiness zones 4 through 9.
This warm-season grass is a perennial plant. It starts growth from seeds and rhizomes beginning in April. Rapid growth is stimulated by fire and increases as summer begins.
Big bluestem is extremely drought-hardy and will continue to grow and reproduce despite high temperatures. This plant flowers throughout much of the summer, July through September, depending on the year.
After a frost, the leaf blades change to a dramatic reddish color. The dead stems will often remain standing throughout the winter, but are prone to falling (lodging) when significant snowfalls accumulate.
Few plants have such a famous connection with the tallgrass prairie of the Great Plains as big bluestem. In its native environment, it may make up the vast majority of the prairie plant community. It also helps build the soil community, as it produces massive stem and root systems that contribute considerable amounts of organic matter when decomposing.
While commonly associated with large grazing mammals such as deer and bison, big bluestem is an important source of food and shelter to many smaller animals. Its seeds are part of the diet of prairie chickens and grassland songbirds, while its stems offer a safe place for birds and insects to lay eggs in the summer. Its value as a shelter plant decreases in the winter, however, as it may collapse under the weight of falling snow.
Big bluestem is well known for its value as livestock forage. It is frequently associated with fast-growing steers, although in spring and summer it is an excellent source of nutrition for all classes of livestock. In fall, it becomes coarse and loses a considerable amount of its protein content, but remains a good natural source of roughage when supplemented with cool-season grasses. Sow it early in the spring before weeds grow and while the soil is cool. Plant at a rate of seven pounds pure live seed to the acre and roll the seed firmly into the soil at 1/4 to 1/2 inch deep to ensure good germination rates. Give big bluestem plenty of time to establish itself—about two years—before grazing. Afterward, maintain the health of bluestem pasture as follows:
- Burn in spring to eliminate weed competition.
- Do not begin grazing until the grass is at least 14 inches tall.
- Use rotational grazing.
- Stop grazing soon enough to leave at least 6 inches of leaves and stubble on the plants at all times.
- Allow the plants to rest before each frost to store reserve energy for the winter.
- Every second or third summer, let the plants rest and produce seeds.
When raising bluestem for hay, cut in early to mid-summer while the plants are in the boot stage (when a newly developed seedhead just starts to poke out of the uppermost leaf sheath) to maximize nutritional value. Leave three to four inches of stubble. Once the grass recovers, it can be lightly grazed for about a month, provided adequate residuals are left.
Big bluestem is a common choice for conservation projects, such as prairie restoration, erosion control, and wildlife habitat creation. Its extensive root system suits it ideally to protecting the soil from wind damage. For these purposes, it is typically mixed with other native warm-season species when planted.
Gardeners who enjoy working with native plants may like to give big bluestem a try, as well. Remember that it will grow tall—it will be most effective when planted as a rear border. Give it plenty of time to establish itself. Regular watering will help it germinate quickly, but be careful not to overdo as the plants mature. It will start to achieve its most ornamental appearance after the second year of growth.
Native Americans had many uses for big bluestem. It made an adequate substitute for rope when tying support poles for dwellings. It could be laid over ripening fruit or under drying fruit. Extracts could be prepared from the leaves to be applied externally to treat pain or fever. Even the roots could be used medicinally for digestive pain.
There are no major hazards associated with big bluestem. The dormant grass can be a fire hazard if allowed to collect around buildings.
Big bluestem may be considered a weed in a few areas (not Kansas).
Big bluestem is very distinctive and should not present a significant identification problem. The inflorescence is a giveaway. In plants that have not yet flowered, look for bluish or purplish coloring toward the base of the stem and white hairs on the stem and upper surface of the leaf, particularly near the sheath.
Parts of a Grass Plant: A Glossary
Definitions for technical terms used in this post.