Ageratum houstonianum

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Flossflower
Ageratum houstonianum (alverson).jpg
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Tribe: Eupatorieae
Genus: Ageratum
Species: A. houstonianum
Binomial name
Ageratum houstonianum
Mill.
Ageratum houstonianum 2.1 R.jpg

Ageratum houstonianum (flossflower, bluemink, blueweed, pussy foot, Mexican paintbrush) syn. Ageratum mexicanum Hort. is a cool-season annual plant often grown as bedding in gardens. The plant grows to 0.3–1 m high, with ovate to triangular leaves 2–7 cm long, and blue flowers (sometimes white, pink, or purple). The flower heads are borne in dense corymbs. The ray flowers are threadlike, leading to the common name.[1]

The plant is native to Central America and adjacent parts of Mexico, but has become an invasive weed in other areas.[2][3]

Ageratum has evolved an ingenious method of protecting itself from insects; it produces a precocene compound which interferes with the normal function of the corpus allatum, the organ responsible for secreting juvenile hormone. This chemical triggers the next molting cycle to prematurely develop adult structures, and can render most insects sterile if ingested in large enough quantities. [4]

Varieties[edit]

  • A. houstonianum var. angustatum B.L. Rob.[5]
  • A. houstonianum f. isochroum
  • A. houstonianum f. luteum
  • A. houstonianum var. muticescens
  • A. houstonianum f. niveum
  • A. houstonianum f. normale
  • A. houstonianum var. typicum
  • A. houstonianum f. versicolor

The cultivars 'Blue Danube',[6] 'Blue Horizon'[7] and 'Hawaii White'[8] have gained the Royal Horticultural Society's Award of Garden Merit.

Toxicity[edit]

Ageratum houstonianum is toxic to grazing animals, causing liver lesions.[9][10] It contains pyrrolizidine alkaloids.[11]

Weed risk[edit]

A. houstonianum is prone to becoming a rampant environmental weed when grown outside of its natural range. It has become an invasive weed in the eastern USA, Australia, Europe, Africa, China, Japan and New Zealand.[12]

References[edit]

  1. ^ New South Wales Flora Online, Ageratum houstonianum
  2. ^ "Ageratum houstonianum". Flora of North America. 
  3. ^ Species profile
  4. ^ I. Kiss et al. (September 1988), Biological activity of precocene analogues on Locusta migratoria, Cellular and Molecular Life Sciences 44: 790–792, doi:10.1007/BF01959168 
  5. ^ JSTOR Plant Science
  6. ^ RHS Plant Selector Ageratum houstonianum 'Blue Danube' AGM / RHS Gardening
  7. ^ RHS Plant Selector Ageratum houstonianum 'Blue Horizon' AGM / RHS Gardening
  8. ^ RHS Plant Selector Ageratum houstonianum 'Hawaii White' AGM / RHS Gardening
  9. ^ Acamovic, T., Stewart, C.S., Pennycott, T.W.,"Poisonous Plants and Related Toxins", 2004
  10. ^ Noa, M., Sanchez, L.M., Durand, R., "Ageratum houstonianum toxicosis in Zebu cattle", Veterinary and human toxicology, 2004, vol.46, no4, pp.193-195.
  11. ^ Wiedenfeld H, Andrade-Cetto A., "Pyrrolizidine alkaloids from Ageratum houstonianum Mill.", Phytochemistry, 2001 Aug, pp1269-71 [1]
  12. ^ Global Compendium of Weeds, Ageratum houstonianum (Asteraceae)