Ageratum houstonianum Mill

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Ageratum houstonianum

Picture: Bart Wursten
Vumba Rd, nr Mountain Lodge

Ageratum houstonianum

Picture: Bart Wursten
By road from Swynnerton Memorial to main road, Chirinda Forest

Ageratum houstonianum

Picture: Mark Hyde
By Mukuvisi River, Mukuvisi Woodlands, Harare

Ageratum houstonianum

Picture: Mark Hyde
By Mukuvisi River, Mukuvisi Woodlands, Harare

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Species details: Click on each item to see an explanation of that item (Note: opens a new window)

Synonyms: Ageratum conyzoides L. subsp. houstonianum (Mill.) Sahu
Ageratum mexicanum Sims
Common names:
Annual herb, 10-60 cm. Leaves: base usually cordate. Florets purple, occasionally pale lilac to white. Phyllaries 4-5 mm, linear-lanceolate, attenuate, entire, ciliate, the back densely glandular-hairy. Style arms exserted 2 mm or more from corolla tube.
Type location:
Notes: A. houstonianum is a more garden-worthy plant than A. conyzoides, with larger and more strongly coloured capitula. Although it is generally easy to separate these two species from general appearance, it is not so easy to devise reliable and unambiguous key characters.
Derivation of specific name:
Habitat: Roadsides, areas of disturbed ground and by streams.
Altitude range:
Flowering time:Oct - May
Worldwide distribution: Native of Mexico but also a pantropical weed.
Zambian distribution (Flora Zambesiaca):
Zambian distribution (Provinces):
Growth form(s):
Endemic status:
Red data list status:
Insects associated with this species: Hypolimnas misippus (Food plant)
Spot characters: Display spot characters for this species

Beentje, H.J. & Ghazanfar, S.A. (eds.) (2005). Compositae (Part 3) Flora of Tropical East Africa Pages 828 - 832. (Includes a picture).

Fabian, A. & Germishuizen, G. (1997). Wild Flowers of Northern South Africa. Fernwood Press, Vlaeburg. Page 436. (Includes a picture).

Henderson, L. (2001). Alien weeds and invasive plants Plant Protection Research Institute Handbook No. 12. Plant Protection Research Institute, Agricultural Research Council, South Africa. Page 39. (Includes a picture).

Mapaura, A. & Timberlake, J. (eds) (2004). A checklist of Zimbabwean vascular plants Southern African Botanical Diversity Network Report No. 33 Sabonet, Pretoria and Harare Page 23.

Pooley, E. (1998). A Field Guide to the Wild Flowers of KwaZulu-Natal and the Eastern Region. Natal Flora Publications Trust. Durban. Page 498. (Includes a picture).

Other sources of information about Ageratum houstonianum:

Our websites:

Flora of Caprivi: cultivated Ageratum houstonianum
Flora of Malawi: Ageratum houstonianum
Flora of Mozambique: Ageratum houstonianum
Flora of Zimbabwe: Ageratum houstonianum
Flora of Zimbabwe: cultivated Ageratum houstonianum

External websites:

African Plants: A Photo Guide (Senckenberg): Ageratum houstonianum
African Plant Database: Ageratum houstonianum
BHL (Biodiversity Heritage Library): Ageratum houstonianum
EOL (Encyclopedia of Life): Ageratum houstonianum
GBIF (Global Biodiversity Information Facility): Ageratum houstonianum
Google: Web - Images - Scholar
iNaturalist: Ageratum houstonianum
IPNI (International Plant Names Index): Ageratum houstonianum
JSTOR Plant Science: Ageratum houstonianum
Mansfeld World Database of Agricultural and Horticultural Crops: Ageratum houstonianum
Plants of the World Online: Ageratum houstonianum
Tropicos: Ageratum houstonianum
Wikipedia: Ageratum houstonianum

Copyright: Mike Bingham, Annette Willemen, Bart Wursten, Petra Ballings and Mark Hyde, 2011-24

Bingham, M.G., Willemen, A., Wursten, B.T., Ballings, P. and Hyde, M.A. (2024). Flora of Zambia: Species information: Ageratum houstonianum., retrieved 13 June 2024

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