Yellow bluestem is a perennial, clump-forming, small, blue-gray graceful grass, with flowering stems up to 4 feet tall. Leaf blades are yellow-green, flat or folded, usually smooth. Leaf sheaths are rounded. The nodes may be smooth or with short hairs. Blooms in Missouri in late June to July, far earlier than our native bluestems. The inflorescence is silvery, reddish purple, and the length of the side branches exceeds the length of the central stem. Blooms late June through July.
Similar species: The similarly invasive Caucasian bluestem (Bothriochloa bladhii) is smaller and has blue-gray leaves; the leaf sheaths are rounded and leaf blades flat or somewhat U-shaped in cross-section; nodes are purple-tinged and may be smooth or with short hairs. Although its inflorescence is similar to yellow bluestem, the side branches are shorter than the central stem (resembling a miniature version of Johnson grass, another invasive grass, which blooms at the same time).
Height: to 4 feet.
Potentially statewide. Documented to be escaping in Howell County and also likely found in other counties.
Habitat and Conservation
Old World bluestems (both yellow and Caucasian species) can be found near disturbed roadsides, in pastures, and even in high-quality prairie and glade habitats. They are very difficult to eradicate once established.
Status
Invasive. Yellow bluestem is a warm-season perennial grass native to southern Europe and Asia. It and Caucasian bluestem were brought to the United States in the early 1900s for use as forage grass and to control erosion. Unfortunately, that effort to “improve” rangeland backfired. These grasses are less palatable and less nutritious to cattle than our native warm-season grasses, and once established, the invasive species are almost impossible to eradicate.
Life Cycle
Yellow bluestem spreads by root and seed. Because foragers and grazers prefer native grasses, the invasive Old World bluestems have a competitive advantage. These aggressive weeds can also cause an altered carbon-to-nitrogen ratio in the soil that inhibits the growth of native plants.
Human Connections
Despite its inferiority as fodder, invasive nature, and negative effect on cultivated and natural lands, unprincipled seed-sellers still sometimes recommended yellow bluestem to Missouri cattle ranchers because it can withstand close grazing. Its use for erosion control is highly discouraged.
Ecosystem Connections
Both species of Old World bluestems have been shown to alter soil function and biota, thereby suppressing the growth of native grasses. They form much thicker sod than native grasses, making them unsuitable for quail nesting or cover.
