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Columbus Grass

Columbus grass1

Johnson Grass

Giant reed plant

Giant reed flowers

Common reed plant

Common reed seed head

    


status:

Columbus grass (Sorghum X almum) is listed as noxious in class 4 in Upper Lachlan and Southern Slopes LCAs in the Southern Tablelands and South East Region.

Description

Columbus grass is a very robust perennial grass to 3.5 metres in height, which has underground runners (rhizomes) similar to Johnson Grass, but larger. Leaves are up to 50cm or more long and 2cm wide, with the margins and midrib often whitish. The flowering head is 25cm long, with spreading branches. Flowers are pale green to red-brown. The first photo is Columbus grass, the second is the very similar Johnson grass, the next two are the weed giant reed and the final two are the native common reed (see under Look-alikes below).  (Columbus grass photo by Greg Keighery, Dept of Conservation and Land Management, W.A.)
This is a hybrid between the subtropical species Johnson grass (Sorghum halepense) and grain sorghum. It was sown in the subtropics for forage but soon became naturalised. In NSW it is mostly found in the north.

Dispersal

Seed sticks to animals and clothing and floats on water. It may also pass intact through animals, to be spread in their droppings. It may also be spread in contaminated hay.
It may also be spread in soil on vehicle tyres and machinery, and as a contaminant of agricultural produce such as hay or grain. Locally plants spread by rhizomes, and pieces of rhizome may be spread during cultivation or roadworks.

Look-alikes

Johnson grass (Sorghum halepense) is similar in appearance, but smaller. It is listed as noxious in class 4 in the same LCAs.

Giant reed (Arundo donax) is a little similar, but more bamboo-like in appearance, with fluffier white seed heads. It grows up to 4m high, in big clumps of arching stems.

The native common reed (Phragmites australis), which grows in wet areas, either in or adjacent to water, 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 3m high, though usually more like 2m.

Control

Dig or spot spray new infestations before seeding. Once a dense infestation has developed, repeated cultivation to exhaust the rhizomes or an integrated control program using cultivation, competing crops and herbicides may be needed. Grass-specific herbicides can control it in broadleaf crops. In difficult terrain where cultivation is not feasible herbicides are the only possible method. Burn or slash first to reduce bulk and spray regrowth in mid to late summer.