Species
Ageratum houstonianum
Etymology
Ageratum: From the Greek a- 'without' and geras 'old', meaning not aging, possibly referring to the fact that the flowers do not wither readily
houstonianum: Named after the genus Houstonia, which is named after the English botanist Dr William Houston.
Common Name(s)
blue billy goat weed
Authority
Ageratum houstonianum Mill.
Family
Asteraceae
Flora Category
Vascular - Exotic
Structural Class
Dicotyledonous Herbs - Composites
Habitat
Terrestrial. Prefers open sunny spots along forest edges.
Features
Erect or ascending annual herb, up to 1 m tall somewhat woody toward base. leaves on a short petiole up to 20 mm long. Leaves hairy and glandular especially on lower surface, ovate with crenate-serrate margins up to about 50 x 60 m. Blue flowers in dense clusters. Seeds sparsely hairy, black up to 1.8 mm long.
Similar Taxa
Is distinctive within the Asteracea due to the blue flowers, and petiolate, hairy leaves with toothed margins.
Flowering
January, February, March, April, May, June, July, August, September, October, November, December
Flower Colours
Blue
Year Naturalised
1888
Origin
Mexico, C. and tropical America
Reason for Introduction
Ornamental
Life Cycle and Dispersal
Annual. Produces small dry seed, sparsely hairy at one end. Dispersed by people and the wind.
References and further reading
Johnson, A. T. and Smith, H. A (1986). Plant Names Simplified: Their pronunciation, derivation and meaning. Landsman Bookshop Ltd: Buckenhill, UK.
This page last updated on 8 Aug 2013