Sandbur, Cenchrus longispinus

Life Cycle

Annual.

Propagation

Reproduces only by seed.

Stems

Commonly 10-60cm long, erect or spreading or lying on the ground.

Leaves

Leaves: flat or margins inrolled, usually constricted and partially twisted at the junction with the leaf sheaths, 2-12 cm long, mostly hairless but rough in one direction. Leaf sheaths split with overlapping margins. On young plants, these margins are membranous and without hair but on upper leaf sheaths of older stems are membranous and usually also with few to many hairs, 1-2 mm long; ligule a fringe of hair, mostly less than 1 mm long; tuft of short and long hair on each side of the collar at the junction between blade and sheath; no auricles.

Flowers and Fruit

Inflorescence a group of spiny burs at the end of each stem; each bur 4-6mm long, containing 1 or 2 "seeds" and covered with extremely sharp spines (2-6mm long) with backward-pointing barbs which anchor into skin, etc., the whole bur breaking off when mature. Flowers from August to September.

Habitat

A native species. As the name implies, this grass species is found predominately on sandy soils throughout southern Ontario. Though normally found along sandy beaches, sand dunes, riverbanks and roadsides, it has been a problem in tobacco fields, other row crops and occasionally in lawns and gardens on sandy soils.

Distinguishing Features

Once long-spined sandbur is in flower (or headed) it cannot be confused with any other annual grass as there is a group of sharp, spiny burs at the end of each stem. At the seedling stage, this weed could be confused with one of the foxtails since it has a hairy ligule. However, its leaf sheath is split with membraneous margins, a characteristic that distinguishes it from the foxtail species. One trick to identifying sandbur seedlings is to dig around, or dig up the emerged seedlings. If the population is in fact long-spined sandbur you will more than likely see a number of burs either in the soil, or at the base of the seedling.


Figure #1.

Long-spined sandbur. A. Plant. B. Leaf-base. C. Bur enclosing spikelet.


Figure #2.

Sandbur shoot.


Figure #3.

Sandbur seedling.


Figure #4.

Young sandbur plant.


Figure #5.

Leaf sheath of sandbur.


Figure #6.

Close-up of sandbur leaf.


Figure #7.

Sandbur ligule.


Figure #8.

Sandbur red stem base.