Ageratum houstonianum (flossflower, bluemink, blueweed, pussy foot, Mexican paintbrush) 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 flowerheads (sometimes white, pink, or purple). The flower heads are borne in dense corymbs. The ray flowers are threadlike, leading to the common name.
The plant is native to Central America and adjacent parts of Mexico, but has become an invasive weed in other areas.
Ageratum has evolved an ingenious method of protecting itself from insects; it produces a methoprene-like 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.
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Varieties
- A. houstonianum var. angustatum B.L. Rob.
- 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', 'Blue Horizon' and 'Hawaii White' have gained the Royal Horticultural Society's Award of Garden Merit.
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Toxicity
Ageratum houstonianum is toxic to grazing animals, causing liver lesions. It contains pyrrolizidine alkaloids.
Weed risk
Ageratum houstonianum is prone to becoming a rampant environmental weed when grown outside of its natural range. It has become an invasive weed in the United States, Australia, Europe, Africa, China, Japan, New Zealand, and the Philippines.
Source of the article : Wikipedia
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