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Overview

Comprehensive Description

Miscellaneous Details

"Notes: Western Ghats & Eastern Ghats, Naturalized, Native of Tropical America"
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Description

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.
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Source: Flora of Zimbabwe

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Distribution

National Distribution

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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"Kerala: Idukki, Kollam, Pathanamthitta, Thrissur Tamil Nadu: Coimbatore, Dindigul, Nilgiri, Salem, Theni"
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Distribution in Egypt

Nile region.

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Global Distribution

Central America.

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Worldwide distribution

Native of Mexico but also a pantropical weed.
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Source: Flora of Zimbabwe

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Native of Mexico; pantropical weed.
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Physical Description

Morphology

Description

Annuals, 30–80 cm (fibrous-rooted). Stems erect to decumbent, sparsely to densely pilose. Leaf blades deltate to ovate, mostly 3–8 × 2.5–4 cm, margins toothed, abaxial faces sparsely to densely pilose, not evidently gland-dotted. Peduncles viscid-puberulent, pilose, and stipitate-glandular. Involucres ca. 4 × 5–6 mm. Phyllaries narrowly lanceolate (0.6–1 mm wide), stipitate-glandular, sparsely to densely pilose, eciliate or inconspicuously ciliate, tips gradually tapering, indurate-subulate, 0.8–2 mm. Corollas usually lavender, rarely white. Cypselae sparsely strigoso-hispidulous; pappi of 5 distinct, oblong scales 2–3 mm. 2n = 20.
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Elevation Range

1300 m
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Diagnostic Description

Diagnostic

Habit: Herb
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Synonym

Ageratum conyzoides Linnaeus var. mexicanum (Sims) de Candolle
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Ecology

Habitat

Nile and canal banks.

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Associations

Insects whose larvae eat this plant species

Hypolimnas misippus (Common diadem)
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Population Biology

Frequency

Occasional
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Ageratum houstonianum

The following is a representative barcode sequence, the centroid of all available sequences for this species.


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Statistics of barcoding coverage: Ageratum houstonianum

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: NNA - Not Applicable

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NatureServe Conservation Status

Rounded Global Status Rank: GNR - Not Yet Ranked

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Wikipedia

Ageratum houstonianum

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]

Contents

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)



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Notes

Comments

Ageratum houstonianum is apparently native to southeastern Mexico and Central America; the North American plants are escapes and naturalized from cultivars. M. F. Johnson (1971) observed that forma isochroum (B. L. Robinson) M. F. Johnson (type from the state of Veracruz, Mexico) sometimes may be nearly eglandular.
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