Ageratina thyrsiflora

(Greene) R. M. King & H. Robinson

Phytologia 19: 227. 1970.

Common names: Congested snakeroot
Basionyms: Kyrstenia thyrsiflora Greene Leafl. Bot. Observ. Crit. 1: 9. 1903
Treatment appears in FNA Volume 21. Treatment on page 553. Mentioned on page 548.

Perennials or subshrubs, 50–100 cm. Stems erect (usually forming compact ‘bushlets’), finely and evenly puberulent (hairs minute, bent). Leaves usually alternate, sometimes subopposite (densely overlapping internodes); petioles 3–20 mm; blades ovatelanceolate to triangular, 2.5–6.5 × 1–2.5 (–3) cm, bases obtuse to cuneate, margins shallowly and coarsely crenate to serrate to subentire, apices rounded-obtuse, abaxial faces hirtellous. Heads clustered (in dense, terminal aggregates). Peduncles 3–8 mm, puberulent. Involucres 2.5–3 mm. Phyllaries: apices acute to obtuse (dark orange-veined), abaxial faces. Corollas white (orange-veined), glabrous. Cypselae hispid.


Phenology: Flowering Sep–Nov.
Habitat: Rocky sites, oak woodland
Elevation: 1000–2200 m

Distribution

V21-1405-distribution-map.gif

Ariz., Mexico (Chihuahua), Mexico (Durango), Mexico (Jalisco), Mexico (Sinaloa), Mexico (Sonora)

Discussion

Ageratina thyrsiflora is known from the United States from a single collection dated 1929 from “near Nogales” in Santa Cruz County. It is recognized by its strict, unbranched or few-branched stems with alternate, densely arranged leaves, relatively small heads densely clustered in terminal aggregates, orange-veined phyllaries and corollas, and closely puberulent stems and petioles (hairs minute, sharply upwardly bent).

Selected References

None.

Lower Taxa

None.

"fine" is not a number.

... more about "Ageratina thyrsiflora"
not tailed +, truncate +, rounded +  and obtuse +
scarious +
usually ovate +  and lanceolate +
usually terete +  and clavate +
indeterminate +  and determinate +
Guy L. Nesom +
(Greene) R. M. King & H. Robinson +
obtuse +  and cuneate +
enlarged +
Kyrstenia thyrsiflora +
3(-5)-nerved +
2.5 cm25 mm <br />0.025 m <br /> (3 cm30 mm <br />0.03 m <br />) +
2.5 cm25 mm <br />0.025 m <br /> (6.5 cm65 mm <br />0.065 m <br />) +
dissected +, lobed +, toothed +  and entire +
ovatelanceolate;triangular +
1cm;2.5cm +
papillate +  and rugose +
(4-)5-angled;10-ribbed +
Congested snakeroot +
scabrellous +
fusiform +  and prismatic +
fertile +  and bisexual +
Ariz. +, Mexico (Chihuahua) +, Mexico (Durango) +, Mexico (Jalisco) +, Mexico (Sinaloa) +  and Mexico (Sonora) +
1000–2200 m +
puberulent +, pilose +, hispidulous +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Rocky sites, oak woodland +
indeterminate +
each +  and sessile +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
campanulate +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
subopposite +  and alternate +
lanceolate +  and lance-linear +
serrate +, dentate +  and entire +
coarsely crenate +  and serrate +
2-carpellate +
persistent +
0.3 cm3 mm <br />0.003 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
0.3 cm3 mm <br />0.003 m <br /> (2 cm20 mm <br />0.02 m <br />) +
Flowering Sep–Nov. +
2-nerved +  and 0-nerved +
8 +  and 30 +
subequal +  and unequal +
bearing subulate enations +, hairy +  and bristly +
exalbuminous +
appendaged +  and truncate +
hirsutulous +
papillate +
Compositae +
Ageratina thyrsiflora +
Ageratina +
species +
obconic +  and campanulate +
50 cm500 mm <br />0.5 m <br /> (100 cm1,000 mm <br />1 m <br />) +