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bluemink, floss flower, Houston's whiteweed

Habit Annuals, 30–80 cm (fibrous-rooted).

erect to decumbent, sparsely to densely pilose.


blades deltate to ovate, mostly 3–8 × 2.5–4 cm, margins toothed, abaxial faces sparsely to densely pilose, not evidently gland-dotted.


viscid-puberulent, pilose, and stipitate-glandular.


ca. 4 × 5–6 mm.


usually lavender, rarely white.


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.


sparsely strigoso-hispidulous;

pappi of 5 distinct, oblong scales 2–3 mm.


= 20.

Ageratum houstonianum

Phenology Flowering Jun–Aug.
Habitat Disturbed sites, mostly coastal
Elevation 0–20 m (0–100 ft)
from FNA
AL; CT; FL; GA; MA; NC; SC; TX; Mexico; Central America [Introduced in North America; introduced, Pacific Islands (Hawaii)]
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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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 21, p. 483.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratum
Sibling taxa
A. conyzoides, A. corymbosum, A. maritimum
Synonyms A. conyzoides var. mexicanum
Name authority Miller: Gard. Dict. ed. 8, Ageratum no. 2. (1768)
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