Scale bar 10mm. Copyright CSIRO
Cotyledon stage, epigeal germination. Copyright CSIRO
10th leaf stage. Copyright CSIRO
Leaves, flowers and fruit. Copyright CSIRO
Gomphocarpus physocarpus E.Mey.
Meyer, E.H.F. (1836) Commentariorum de plantis Africae Australioris 1: 202. Type: South Africa, J. F. Drege; holo: B ? destroyed. Fide Forster (1996) Flora Australia 28: 218.
Asclepias physocarpa (E.Mey.) Schltr., Beiblatt No. 54: 8(1896), Type: ?.
Balloon Cotton Bush; Cotton Bush
Usually flowers and fruits as a single-stemmed shrub 1-2 m tall.
Leaves rather variable, leaf blades about 5-8.5 x 0.9-1.3 cm. Stipules dark, small and inconspicuous, less than 1 mm long. Petiole grooved on the upper surface. Leaves, twigs and petioles produce a milky exudate.
Inflorescences not strictly axillary, arising from the twigs beside the petioles but not in the axil of the petiole. Pedicels about 1.5-2 cm long. Flowers about 10-16 mm diam. Anthers sessile. Ovary clothed in glands or glandular hairs. Each flower with two free carpels but only one appears to be functional.
Seeds about 5 x 2 mm, excavated or flat on one side, testa reticulate, long white silky hairs on the margins. Cotyledons yellow-orange.
Cotyledons about 20 x 8-9 mm. First pair of leaves narrowly ovate, opposite. At the tenth leaf stage: leaves linear or narrowly elliptic, apex acute, base attenuate. All parts of the seedling produce a milky exudate. Stipules small and inconspicuous.
Distribution and Ecology
An introduced weed originally from Africa now naturalized over a wide area of Australia. Altitudinal range from near sea level to 1100 m. In NEQ grows on farmland and disturbed areas of eucalypt forest and occasionally along roads, etc. in rain forest.
A poisonous plant but rarely eaten by domestic animals. Everist (1974).
Herb (herbaceous or woody, under 1 m tall)
Shrub (woody or herbaceous, 1-6 m tall)