Pompom weed

Appearance

This species is rhizomatous with erect stems to 1.3 m tall, and has stem and leaves covered in rough, bristly hairs. It forms dense rosettes of leaves at ground level, suppressing the germination and growth of other species, at the same time producing allelochemicals which adversely affect the growth of neighbouring plants. The plant dies back annually to its root crown, and survives veldfires over the winter period. Its leaves are light green in colour, lanceolate-elliptic in shape, and measure 8 cm x 2 cm. Leaf margins are serrate, the teeth becoming smaller away from the stalk. Flower heads are surrounded by lanceolate, purplish bracts some 8 mm in length. Flowers are large, pink and showy, and exceed the bracts by 6–8 mm. Mature achenes are black and 5 mm long with a pappus of simple bristles.

Naming

The name ''Eupatorium macrocephalum'' was first published in January 1830 by Christian Friedrich Lessing in Linnaea 5: 136–137. 1830. ''"Eupatorium"'' was first used by Linnaeus to honour 'Eupator Dionysius' aka Mithridates, an ancient ruler of Anatolia, while 'macrocephalum' means 'large-headed' and refers to the inflorescence.

Predators

Moths of the genus ''Adaina'' and in particular ''Adaina microdactyla'' , have been investigated as possible biological control agents. Species in the genus include flower borers, leaf feeders and also species that induce stem galls which provide food and accommodation for larvae and pupae. Research at Cedara College of Agriculture has found a rust fungus, ''Puccinia eupatorii'', which invades the seeds and kills the whole plant, including the roots. This rust fungus is specific to ''E. macrocephalum'' and would therefore be ideal as a biological control. Other potential insect agents include a stem-galling thrips, ''Liothrips'' sp., and the moth ''Cochylis campuloclinium''.