Difference between revisions of "Ageratum"

Latest revision as of 11:27, 7 July 2010

Ageratum (pronounced /əˈdʒɛrətəm/ A-gé-ra-tum),^[1] known as Whiteweed, is a genus of 40^[2] to 60 tropical American herbs, annuals and perennials from the Sunflower family Asteraceae, tribe Eupatorieae.

They form tussocks or small hills. They grow to a height of 75 cm. 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.

Most species are native to Central America and Mexico but four are native to the United States.^[2]

Ageratums as garden plants

They are grown for their flowers, especially the Flossflower (Ageratum houstonianum). Many are useful for bedding and bordering or in rock gardens.

Most common ageratums, "Hawaii" for example, are a short 6-8 inches when full grown. Tall ageratum are also available in seed catalogues, but rarely in retail stores. 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 Ageratum good candidates for rock gardens, flower beds, and containers.

Ageratum grow well in the 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. They are excellent for beginner gardeners.

Toxicity

Several species of Ageratum are toxic, containing pyrrolizidine alkaloids. Ageratum houstonianum and Ageratum conyzoides cause liver lesions and are tumorigenic.^[3][4][5][6]

Weed risk

Ageratum are prone to becoming rampant environmental weeds when grown outside of their natural range.^[7][8]

Species

• Ageratum arsenei
• Ageratum candidum
• Ageratum chortianum
• Ageratum connatifolius
• Ageratum conyzoides: Billy-Goatweed, Tropical Whiteweed, Mexican Ageratum
• Ageratum corymbosum: Flattop Whiteweed, Butterfly Mist
  • Ageratum corymbosum f. album
  • Ageratum corymbosum f. euryphyllum
  • Ageratum corymbosum var. jaliscense
  • Ageratum corymbosum f. lactiflorum
  • Ageratum corymbosum var. longipetiolatum
  • Ageratum corymbosum var. subsetiferum
• Ageratum elassocarpum
• Ageratum ellepticum
• Ageratum gaumeri
• Ageratum guatemalense

• Ageratum heterolepis
• Ageratum hondurense
• Ageratum houstonianum : Bluemink, Flossflower, Garden Ageratum, Blueweed).
  • Ageratum houstonianum var. angustatum
  • Ageratum houstonianum f. isochroum
  • Ageratum houstonianum f. luteum
  • Ageratum houstonianum var. muticescens
  • Ageratum houstonianum f. niveum
  • Ageratum houstonianum f. normale
  • Ageratum houstonianum var. typicum
  • Ageratum houstonianum f. versicolor
• Ageratum iltisii
  • Ageratum latifolium var. galapageium
• Ageratum littorale : Cape Sable Whiteweed
  • Ageratum littorale f. album
  • Ageratum littorale var. hondurense
  • Ageratum littorale f. setigerum
• Ageratum lucidum
• Ageratum lundellii
• Ageratum maritimum
  • Ageratum maritimum f. calvum
• Ageratum meridensis
  • Ageratum mexicanum var. majus
• Ageratum molinae
• Ageratum munaense
• Ageratum nelsonii
• Ageratum oliveri
• Ageratum peckii
• Ageratum perplexans
• Ageratum platypodum
• Ageratum radicans
• Ageratum reedii
• Ageratum rhytidophyllum
• Ageratum riparium
• Ageratum rugosum
• Ageratum serratum
• Ageratum sordidum
• Ageratum stachyofolium
• Ageratum standleyi
• Ageratum tehuacanum
• Ageratum tomentosum
• Ageratum viscosum
• Ageratum wendlandii
• Ageratum wrightii

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.^[9]

References

1. ↑ Sunset Western Garden Book, 1995:606–607
2. ↑ ^{2.0 2.1} "Ageratum". Flora of North America. 
3. ↑ Acamovic, T., Stewart, C.S., Pennycott, T.W.,"Poisonous Plants and Related Toxins", 2004
4. ↑ Noa, M., Sanchez, L.M., Durand, R., "Ageratum houstonianum toxicosis in Zebu cattle", Veterinary and human toxicology, 2004, vol.46, no4, pp.193-195.
5. ↑ 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]
6. ↑ 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]
7. ↑ Global Compendium of Weeds, Ageratum conyzoides (Asteraceae) [3]
8. ↑ Global Compendium of Weeds, Ageratum houstonianum (Asteraceae) [4]
9. ↑ Schilling, Edward E. (2008). "Paneroa, A New Genus of Eupatorieae (Asteraceae) from Mexico". Novon a Journal for Botanical Nomenclature. 18: 520. doi:10.3417/2007173. 

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