What Does It Look Like?
What is it?
Columbus Grass (Sorghum × almum) is a very robust perennial grass growing to 3.5 m in height, with upright stems rising from thick, weakly spreading underground stems (rhizomes). The dark green leaves grow to 50 cm or more long and 2 cm wide, with the margins and mid-rib often whitish (Parsons & Cuthbertson 2001).
The flowering head is up to 25 cm long, pale green to red-brown with spreading branches and branchlets which bear the flower clusters (spikelets). The clusters are arranged in pairs or triplets at the ends of the branchlets with one cluster of each pair or triplet being unstalkled and fertile and the others stalked and sterile. The fertile cluster is 5–7 mm long with or without a bristle. The sterile clusters are narrower and 6–8 cm long. The seeds are reddish brown to black, ovoid and 3.5–4 mm long (Harden 1993; Parsons & Cuthbertson 2001).
For further information and assistance with identification of Columbus Grass contact the herbarium in your state or territory.
Flower colour
Red, Green
Growth form (weed type/habit)
Grass
Where it currently grows? Preferred habitat
Columbus Grass grows in subtropical, semi-arid high fertility soils ranging from deep sands to heavy clays. It is naturalized as a weed mostly along roadsides and fence lines (Parsons & Cuthbertson 2001).
Are there similar species?
Columbus Grass looks very similar to Johnson Grass (Sorghum halepense) but is a larger plant (3.5 m tall compared to 2 m for Johnson Grass). Their spikelets and seed are very difficult to tell apart in mixed samples (Parsons & Cuthbertson 2001; Southern Tablelands and South Coast Noxious Plants Committee Undated).
Giant Reed (Arundo donax) is a little similar, but more bamboo-like in appearance, with fluffier white seed heads. It grows up to 4 m high, in big clumps of arching stems (Southern Tablelands and South Coast Noxious Plants Committee Undated).
Columbus Grass is also similar to the native Common Reed (Phragmites australis), which grows in wet areas, either in or adjacent to water. It has a similar erect leafy appearance, but the seed heads are a cohesive fluffy clump rather than having obvious branching. It can grow up to 3 m high, though usually more like 2 m (Southern Tablelands and South Coast Noxious Plants Committee Undated).