Ageratum corymbosum

Zuccagni

Cent. Observ. Bot., no. 85. 1806.

Common names: Flat-top whiteweed
Illustrated
Synonyms: Ageratum corymbosum var. jaliscense B. L. Robinson Ageratum salicifolium Hemsley Ageratum strictum
Treatment appears in FNA Volume 21. Treatment on page 482. Mentioned on page 481.

Perennials or subshrubs, 30–100 cm (fibrous-rooted). Stems erect to basally decumbent, puberulent to minutely strigoso-hispid. Leaf-blades ovate to rhombic-lanceolate, 3–8 × 1–3.5 cm, margins toothed, abaxial faces usually puberulent, sometimes minutely strigoso-hispid, densely glanddotted. Peduncles finely puberulent (not pilose), eglandular. Involucres 5–6 mm. Phyllaries narrowly lanceolate (0.4–0.7 mm wide, innermost often 1–1.5 mm longer than outer), finely puberulent, eglandular, tips green or purplish, filiform. Corollas usually blue to lavender, sometimes white. Cypselae glabrous; pappi usually crowns of connate scales with erose margins or tubular portions longer than divisions, rarely with 1 or more awnlike lobes. 2n = 20, 30, 40.


Phenology: Flowering Jul–Oct.
Habitat: Crevices, ledges, cliffs, other rocky sites in canyons, along streams, in desert grasslands, oak-agave, oak, oak-juniper, and pine-oak woodlands
Elevation: (900–)1200–1900 m

Discussion

Habitat information came mostly from collections from Sonora and Chihuahua, Mexico. Ageratum corymbosum grows in all Mexican states except for the extreme southeast. It has been included in various summaries as occurring in Texas; as noted by D. S. Correll and M. C. Johnston (1970), those records apparently were based on a collection by Charles Wright from southwestern New Mexico.

Varieties and forms of Ageratum corymbosum have been recognized (e.g., M. F. Johnson 1971; R. McVaugh 1984). McVaugh wryly noted that extremes of these intergrading infraspecific entities “can be recognized with a little imagination.” The form that reaches the United States (with ovate-lanceolate leaves) is var. jaliscense.

Selected References

None.

Lower Taxa

None.

"fine" is not a number.

... more about "Ageratum corymbosum"
40 +, 30 +  and 20 +
strigoso-hispid +  and puberulent +
not tailed +, truncate +, rounded +  and obtuse +
scarious +
usually ovate +  and lanceolate +
usually terete +  and clavate +
spiciform +, racemiform +, paniculiform +  and corymbiform +
indeterminate +  and determinate +
Guy L. Nesom +
Zuccagni +
decurrent +
not enlarged +
dissected +, lobed +, toothed +  and entire +
deltate;ovate or elliptic +
papillate +  and rugose +
(4-)5-angled;10-ribbed +
less linear;clavate +
Flat-top whiteweed +
white +, usually blue +  and lavender +
prismatic +
fertile +  and bisexual +
Ariz. +, N.Mex. +  and Mexico +
(900–)1200–1900 m +
strigoso-hispid +, puberulent +, pilose +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Crevices, ledges, cliffs, other rocky sites in canyons, along streams, in desert grasslands, oak-agave, oak, oak-juniper, and pine-oak woodlands +
cymiform +  and corymbiform +
in usually determinate , rarely indeterminate , arrays +  and singly +
indeterminate +
each +  and sessile +
campanulate +
0.5 cm5 mm <br />0.005 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
3 cm30 mm <br />0.03 m <br /> (8 cm80 mm <br />0.08 m <br />) +
1 cm10 mm <br />0.01 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
lanceolate +  and lance-linear +
2-carpellate +
persistent +
coroniform +
Flowering Jul–Oct. +
30 +  and 40 +
subequal +  and unequal +
Cent. Observ. Bot., no. +
bearing subulate enations +, hairy +  and bristly +
5 +  and 6 +
aristate +
exalbuminous +
Illustrated +
erect +  and basally decumbent +
appendaged +  and truncate +
hirsutulous +
papillate +
Ageratum corymbosum var. jaliscense +, Ageratum salicifolium +  and Ageratum strictum +
Ageratum corymbosum +
Ageratum +
species +
campanulate +
purplish +  and green +
filiform +
30 cm300 mm <br />0.3 m <br /> (100 cm1,000 mm <br />1 m <br />) +