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Ageratum

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Ageratum
Tropical whiteweed (Ageratum conyzoides)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Tribe: Eupatorieae
Genus: Ageratum
L. 1753 not Mill. 1754 (Plantaginaceae)[1]
Bluemink (Ageratum houstonianum)

Ageratum (/əˈdʒɛrətəm/)[2] (whiteweed in the USA) is a genus of 40[3] to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native to the United States.[3]

They form tussocks or small hills. They grow to a height of 30 in. The opposite leaves are cordate or oval, hairy or tomentose. The margins are slightly toothed or serrate. The leaves form compact clusters.

The fluffy flowers are lavender-blue, pink, lilac, or white; and spread in small compound umbels. They give small, dry fruits.

Cultivation

Ageratums are grown for their flowers, especially A. houstonianum.

Most common ageratums, "Hawaii" for example, are a short 6-8 inches when full grown. Tall ageratum are also available in seed catalogues. They are about 18 inches in height with blue flowers. There is also a medium height snowcapped variety, white top on blue flowers. The blues are most popular and common, but colors also include violet, pink and white. Their size and color makes ageratums good candidates for rock gardens, bedding, and containers. They grow well in sun or partial shade, from early summer to first frost. They are quite easy to grow, producing a profusion of fluffy flowers all season long.

Toxicity

Several species of Ageratum are toxic, containing pyrrolizidine alkaloids. Ageratum houstonianum and Ageratum conyzoides cause liver lesions and are tumorigenic.[4][5][6][7]

Weed risk

Ageratum are prone to becoming rampant environmental weeds when grown outside of their natural range.[8][9]

Species

As of July 2020, Plants of the World online has 40 accepted species:[10]

 

Selected synonyms include:

Segregate genera

The genus Paneroa consists of one species, Paneroa stachyofolia, native to Oaxaca, which was first described in Ageratum but which seems to be more closely related to Conoclinium and Fleischmannia.[11]

References

  1. ^ Tropicos, search for Ageratum
  2. ^ Sunset Western Garden Book, 1995:606–607
  3. ^ a b Nesom, Guy L. (2006). "Ageratum". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 21. New York and Oxford: Oxford University Press – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  4. ^ Acamovic, T., Stewart, C.S., Pennycott, T.W.,"Poisonous Plants and Related Toxins", 2004
  5. ^ Noa, M., Sanchez, L.M., Durand, R., "Ageratum houstonianum toxicosis in Zebu cattle", Veterinary and human toxicology, 2004, vol.46, no4, pp.193-195.
  6. ^ Sani, Y., Bahri, S., "Pathological changes in liver due to the toxicity of Ageratum conyzoides", Penyakit Hewan (Indonesia), 1994, v. 26(48) p. 64-70 [1]
  7. ^ Fu, P.P., Yang, Y.C., Xia, Q., Chou, M.C., Cui, Y.Y., Lin G., "Pyrrolizidine alkaloids-tumorigenic components in Chinese herbal medicines and dietary supplements", Journal of Food and Drug Analysis, Vol. 10, No. 4, 2002, pp. 198-211 [2][permanent dead link]
  8. ^ Global Compendium of Weeds, Ageratum conyzoides (Asteraceae)
  9. ^ Global Compendium of Weeds, Ageratum houstonianum (Asteraceae)
  10. ^ Kew Science Plants of the World Online, retrieved 15 July 2020
  11. ^ Schilling, Edward E. (2008). "Paneroa, A New Genus of Eupatorieae (Asteraceae) from Mexico". Novon a Journal for Botanical Nomenclature. 18 (4): 520–523. doi:10.3417/2007173.
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