Caucasian bluestem (Bothriochloa bladhii)

Synonyms: Andropogon bladhii, Andropogon caucasicus, Andropogon intermedius, Bothriochloa caucasica, Bothriochloa intermedia

Common Names: Australian bluestem, plains bluestem, purple plume grass

Description:

Caucasian bluestem (Bothriochloa bladhii) is a warm-season perennial grass from Africa, Asia, and Australia that was brought to the United States in the early 1900s as a pasture grass and for erosion control [1][2][3]. It escaped cultivation and now forms dense stands across pastures, roadsides, and prairies in the central and southern United States [3][4]. MISIN tracks it because it crowds out native grasses and wildflowers, makes poor wildlife habitat, and is very hard to remove once it takes hold [2][3].

Habit:

Caucasian bluestem is a clump-forming (bunch) grass that grows about 1 to 4 feet tall on slender, upright stems [2]. The narrow leaf blades are 8 to 14 inches long, hairless, and green to bluish ? and they give off a strong turpentine-like smell when crushed, which is one of the surest field checks [2]. Its seed head is the giveaway: a branched, reddish cluster that starts a metallic red and fades to a tawny tan, often shaped a bit like a small Christmas tree [2].

It is a warm-season grass, so it greens up and grows through the heat of summer. It is easiest to spot from mid-summer into fall, when the reddish seed heads stand above the clump and catch the light [2]. The turpentine smell works as a check any time the plant is green. Look for it first along roadsides, pasture edges, and around stock tanks, where new patches often start [2].

At-a-glance cues:

1. Leaf blades smell strongly of turpentine when crushed [2]
2. Reddish, branched seed head that fades to tawny tan, shaped like a small Christmas tree [2]
3. Clump-forming bunchgrass, about 1 to 4 feet tall, with narrow blades 8 to 14 inches long [2]
4. Grows and flowers in summer and fall, often starting along roadsides and around stock tanks [2]

Leaves:

1. Arrangement: blades spread along the stem and at the base of the clump [2]
2. Shape: long and narrow ? 8 to 14 inches (20 to 35 cm) long and only about 1 to 4.5 mm wide [2]
3. Surface: hairless (glabrous); green to bluish [2]
4. Smell: a strong turpentine odor when the leaves are crushed [2]

Stems:

1. Habit: herbaceous (non-woody) warm-season perennial bunchgrass, growing in clumps 1 to 4 feet tall [2]
2. Form: slender, upright stems [2]
3. Roots: fibrous, with short rhizomes (horizontal underground stems) [2]

Flowers:

1. Color: starts a metallic reddish color, fading to tawny tan as it dries [2]
2. Shape: many tiny, silky flower clusters (spikelets) with fine bristles, on a branched head ? no showy petals, as is typical of grasses [2]
3. Arrangement: a branched, finger-like seed head 2 to 6 inches long at the stem tip, shaped a bit like a small Christmas tree [2]
4. Bloom time: mid-summer into fall [2]

Fruit and seeds:

1. Fruit type: a tiny dry grain held in a silky, bristled spikelet (the grass seed) [2]
2. Color: reddish, aging to tawny tan [2]
3. Dispersal: the light, silky seeds are carried by wind, on animals, and on mowers and equipment, and in hay; the plant also creeps short distances by rhizomes [2][3]

Habitat:

Caucasian bluestem is native to the warm regions of the Old World ? across Africa, the Middle East, southern and eastern Asia, and Australia [1]. It was introduced to the United States in the early 1900s as a forage grass and for erosion control, and has since escaped into the wild across the central and southern states [2][3][4].

It grows in pastures, prairies, glades, roadsides, and other open, disturbed ground [2][3]. It tolerates drought and relatively poor soils but does best on heavy clay loam to clay soils [2]. New patches often start in disturbed spots such as roadsides and the bare ground around stock tanks, then spread outward into surrounding grassland [2].

Reproduction:

Caucasian bluestem spreads by both seed and short underground stems [2][3]. It produces many small, silky seeds that blow in the wind and hitch a ride on animals, mowers, vehicles, and baled hay, which is how it jumps to new sites [2]. Once a clump is established, short rhizomes let it widen on its own, and stands thicken into dense sod over time [2][3].

It is a warm-season perennial: it greens up in late spring, grows through summer, and forms its reddish seed heads from mid-summer into fall [2]. For control timing, the key is to act before the seed heads ripen ? cutting or removing plants in summer, before seed sets, keeps a patch from spreading further [2][3].

Impact and Damage:

For landowners, Caucasian bluestem is mainly a pasture and rangeland problem. It is not toxic, but it spreads into dense stands that lower the quality of both pasture and hay, and livestock tend to avoid it because it is less palatable and less nutritious than native bluestems [2]. Its roots are allelopathic, meaning they release chemicals into the soil that hold back the growth of neighboring plants [2].

For natural area stewards, the concern is larger. Caucasian bluestem forms much thicker sod than native grasses and can suppress native plants by changing the soil, letting it take over prairies and glades and even "completely take over" native grasslands if left unchecked [3]. The thick sod also makes poor wildlife habitat ? for example, it does not provide the open structure that bobwhite quail need for nesting and cover [3]. Research on Old World bluestems, including the closely related yellow bluestem, found that bluestem stands held far fewer insects ? on the order of three times less insect food ? and sharply lower numbers of grassland birds than native prairie nearby [5].

Similar species:

Several bunchgrasses look like Caucasian bluestem. The surest checks are the strong turpentine smell of its crushed leaves and its reddish, Christmas-tree-shaped seed head [2].

Yellow bluestem (Bothriochloa ischaemum) is the closest match ? it is the other invasive Old World bluestem, was introduced for the same reasons, and is managed together with Caucasian bluestem [3]. The two are very similar; both form thick sod and crowd out native grasses, so any Old World bluestem is worth reporting [3].

Little bluestem (Schizachyrium scoparium) is a native bunchgrass of similar size that is often confused with it. It turns a rich reddish-bronze in fall, carries fluffy white seed tufts along single stems rather than a branched reddish head, and has no turpentine smell [2][3].

Big bluestem (Andropogon gerardii) is a taller native prairie grass sometimes mistaken for it. It is best told apart by its seed head, which splits into three finger-like spikes resembling a turkey's foot, unlike the softer, branched seed head of Caucasian bluestem [3].

Monitoring and rapid response:

Signs to watch for:

1. Clumps of narrow-leaved grass, 1 to 4 feet tall, whose crushed leaves smell of turpentine [2]
2. Reddish, branched, Christmas-tree-shaped seed heads from mid-summer into fall, fading to tawny tan [2]
3. New patches starting along roadsides, pasture edges, and around stock tanks [2]

What you can do:

1. Dig out small, isolated clumps by hand, removing the roots and short underground stems ? easiest when the soil is moist [2][3]
2. Cut or pull plants before the seed heads ripen in summer, and bag the seed heads so seed cannot scatter [2][3]
3. Catch new patches early ? Caucasian bluestem is far easier to remove when it is a few plants than after it forms thick sod [3]
4. After removing a stand, replant the bare ground with native grasses such as big bluestem or little bluestem to help hold the site [3]
5. For natural areas, volunteer crews should map and remove small outlying patches first, then work across larger stands over several seasons; note that mowing and prescribed fire alone do not control it and can even favor it over native plants [3]

When to call a professional:

1. Established stands or thick sod, which resprout and are very difficult to remove by hand [2][3]
2. Large pasture, prairie, or roadside infestations that need a coordinated, repeated removal plan [3]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Plants of the World Online (POWO), Royal Botanic Gardens, Kew. Bothriochloa bladhii (Retz.) S.T.Blake. powo.science.kew.org
2. Nebraska Invasive Species Council. "Caucasian Bluestem (Bothriochloa bladhii)." neinvasives.com
3. Missouri Department of Conservation. "Old World Bluestem Control." mdc.mo.gov
4. USDA NRCS Plants Database. Bothriochloa bladhii (Retz.) S.T.Blake. plants.usda.gov
5. Hickman KR, Farley GH, Channell R, Steier JE (2006). "Effects of Old World bluestem (Bothriochloa ischaemum) on food availability and avian community composition within the mixed-grass prairie." The Southwestern Naturalist 51(4):524?530. semanticscholar.org

---