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littlehead tarweed, smallhead sneezeweed

Photo is of parent taxon
Habit Annuals, 25–120 cm. Plants 25–80 cm.
Stems

1(2–10), branched distally, moderately to strongly winged, glabrous or sparsely hairy.

Leaves

glabrous or sparsely to moderately hairy (basal withered by flowering);

proximal and mid blades narrowly elliptic to narrowly oblong-elliptic, usually serrate to undulate-serrate, sometimes deeply toothed or laciniate;

distal blades narrowly elliptic to narrowly oblong-elliptic, serrate to undulate-serrate.

proximal and mid blades serrate to undulate-serrate to occasionally deeply toothed or laciniate, glabrate;

distal blades glabrous or sparsely to moderately hairy.

Peduncles

1.8–8 cm, moderately hairy.

1.5–8 cm, usually projecting terminal heads well beyond foliage.

Involucres

globoid to usually ovoid, 4–12 × 4–12 mm.

8–12 × 8–12 mm.

Ray florets

7–13, pistillate, fertile;

corollas usually yellow throughout, sometimes reddish proximally and yellow distally, 2.6–9.1 × 1.5–6.7 mm.

9–13;

corollas usually yellow throughout, sometimes reddish proximally and yellow distally, 2.7–9.1 × 1.5–6.7 mm.

Disc florets

120–400+;

corollas yellow to yellow-green proximally, brown to reddish brown distally, 1.2–2.4 mm, lobes (4–)5.

200–400+;

corollas 1.7–2.4 mm, lobes 5.

Phyllaries

(connate proximally) moderately hairy.

Heads

20–300+ per plant, in paniculiform arrays.

20–100+ per plant.

Cypselae

0.7–1.4 mm, moderately hairy;

pappi of usually 6 entire, non-aristate scales (0.2–)0.3–0.7 mm.

Pappi

0.4–0.7 mm.

2n

= 26.

Helenium microcephalum

Helenium microcephalum var. oöclinium

Phenology Flowering (Mar–)Apr–Jun(–Dec).
Habitat Sandy or clay soils, ditches, washes, around ponds and lakes, along streams
Elevation 500–1900 m (1600–6200 ft)
Distribution
from FNA
AZ; NM; OK; TX; n Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
TX; Mexico (Coahuila, Nuevo León, Durango, San Luis Potosí)
Discussion

Varieties 2 (2 in the flora).

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

Key
1. Peduncles 1–3.5 cm, projecting terminal heads barely beyond foliage; involucres 4–8 × 4–8 mm
var. microcephalum
1. Peduncles 1.5–8 cm, usually projecting terminal heads well beyond foliage; involucres 8–12 × 8–12 mm
var. oöclinium
Source FNA vol. 21, p. 433. FNA vol. 21, p. 434.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Gaillardiinae > Helenium Asteraceae > tribe Heliantheae > subtribe Gaillardiinae > Helenium > Helenium microcephalum
Sibling taxa
H. amarum, H. arizonicum, H. autumnale, H. bigelovii, H. bolanderi, H. brevifolium, H. campestre, H. drummondii, H. elegans, H. flexuosum, H. linifolium, H. pinnatifidum, H. puberulum, H. quadridentatum, H. thurberi, H. vernale, H. virginicum
H. microcephalum var. microcephalum
Subordinate taxa
H. microcephalum var. microcephalum, H. microcephalum var. oöclinium
Synonyms H. oöclinium
Name authority de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 667. (1836) (A. Gray) Bierner: Sida 5: 47. (1972)
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