Weed Identification

Australia > > Narrow-Leaf Cotton Bush

Narrow-Leaf Cotton Bush

Gomphocarpus fruticosus

Alternative Name(s): Swan Plant

Family: Asclepiadaceae.

Form: Herb

Origin: Native of Africa, Arabia and Mediterranean.

Flowers/Seedhead: Inflorescence a drooping umbel of flowers. Flowers all year round.

Description: Erect perennial shrub to 2 m high. Stems densely covered with apressed short weak soft hairs when young, becoming hairless with age. Leaves 412.5 cm long, 0.51.5 cm wide, upper and lower surfaces with scattered hairs; on leaf stalk to 1 cm long. Fruit a green pod initially, turning brown with age, covered with soft spines to 1 cm long, splitting to release seeds; pod with inner wall separated from outer wall by an air space and seeds within inner chamber; pod stalk S-shaped. Seeds numerous, ovoid, flat, about 0.6 cm long and ending in a tuft of white silky hairs about 3 cm long.

Distinguishing features: Distinguished by shrub habit; milky latex; lanceolate opposite leaves; flowers white to cream; fruit a thin walled inflated ovoid pod, 47 cm long, 1.53 cm wide, ending in a tapering point.

Dispersal: Spreads by seeds and lateral roots.

Confused With: Balloon Cotton Bush, Gomphocarpus physocarpus, that has ball-shaped pods without a tapering point and Broad-Leaf Cotton Bush, Gomphocarpus cancellatus, that has inner surface of pods without spines.


Inflated fruit with long soft bristles, white
flowers, caterpillar of Wanderer Butterfly
photo I.Walker

Notes: Poisonous to stock, but seldom eaten. Hybridises with Balloon Cotton Bush with hybrids intermediate in appearance. Cotton Bush is a preferred food for caterpillars of the Wanderer Butterfly, Danaus plexippus, but they do not control the plant.

References:

    Noxious Weeds of Australia. W. Parsons and E. Cuthbertson, 1992, pages 179182.


Wanderer Butterfly
Danaus plexippus

Pods & seeds with silky hairs

Linear leaves & inflated pod

This weed has been included in the WEEDeck field guide as card H32

More information about WEEDeck is available from Sainty & Associates Pty. Ltd.

 

Australia > > Narrow-Leaf Cotton Bush

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