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blunt-sepal starwort, obtuse starwort, Rocky Mountain chickweed, Rocky Mountain starwort

American chickweed, American starwort

Habit Plants perennial, creeping, often matted but not forming cushions, rhizomatous. Plants perennial, forming loose, prostrate mats, from rhizomatous rootstocks.
Stems

prostrate, branched, 4-sided, 3–23 cm, internodes equaling or longer than leaves, glabrous, rarely pilose.

spreading, branched, very leafy, 4-angled, 10–20 cm, short glandular-puberulent on internodes.

Leaves

sessile or short-petiolate;

blade broadly ovate to elliptic, 0.2–1.2 cm × 0.9–7 mm, base round or cuneate, margins entire, apex acute, shiny, glabrous or ciliate near base.

sessile;

blade ovate to ovate-lanceolate, widest at or above middle, 8–30 × 2–13 mm, base round to cuneate, margins not scarious, apex usually obtuse, viscid.

Inflorescences

with flowers solitary, axillary;

bracts absent.

terminal, 1–5-flowered, very leafy cymes;

bracts foliaceous.

Pedicels

spreading, 3–12 mm, glabrous.

ca. 10 mm in flower, elongating, recurved, and tortuous in fruit, glandular-pubescent, pushing capsule into substrate.

Flowers

1.5–2 mm diam.;

sepals 4–5, veins obscure, midrib sometimes apparent, ± ovate, 1.5–3.5 mm, margins narrow, scarious, apex ± obtuse, glabrous;

petals absent;

stamens 10 or fewer;

styles 3(–4), curled, shorter than 0.5 mm.

5–10 mm;

sepals 5, obscurely veined, ovate-obtuse, 3–5 mm, margins narrow, scarious, glandular-pubescent;

petals 5, 4–6 mm;

stamens 5;

styles 3, ascending, equaling petals.

Capsules

green to pale straw colored, translucent, globose to broadly ovoid, 2.3–3.5 mm, 1.9–2 times as long as sepals, apex obtuse, opening by 6 valves;

carpophore absent.

green to straw colored, broadly ovoid to globose, 5–6 mm, apex obtuse, tardily dehiscent with 3 valves;

carpophore absent.

Seeds

grayish black, broadly elliptic, 0.5–0.7 mm diam., finely reticulate.

3–6, rusty brown, ± ovate, ca. 2.5 mm diam., finely tuberculate.

2n

= 26, 52, ca. 65, ca. 78.

Stellaria obtusa

Stellaria americana

Phenology Flowering late spring–summer. Flowering late Jul–Aug.
Habitat Moist areas in woods, shaded edges of creeks, talus slopes Rocky slopes, talus
Elevation 300-3400 m (1000-11200 ft) 1400-2800 m (4600-9200 ft)
Distribution
from FNA
CA; CO; ID; MT; OR; UT; WA; WY; AB; BC
[WildflowerSearch map]
[BONAP county map]
from FNA
MT; AB
[BONAP county map]
Discussion

Stellaria americana is remarkable for its tortuous fruiting pedicels, which push the opening capsule with its small number of large seeds into the substrate.

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

Source FNA vol. 5, p. 110. FNA vol. 5, p. 100.
Parent taxa Caryophyllaceae > subfam. Alsinoideae > Stellaria Caryophyllaceae > subfam. Alsinoideae > Stellaria
Sibling taxa
S. alaskana, S. alsine, S. americana, S. borealis, S. calycantha, S. corei, S. crassifolia, S. crispa, S. cuspidata, S. dicranoides, S. fontinalis, S. graminea, S. holostea, S. humifusa, S. irrigua, S. littoralis, S. longifolia, S. longipes, S. media, S. neglecta, S. nitens, S. pallida, S. palustris, S. parva, S. porsildii, S. pubera, S. ruscifolia, S. umbellata
S. alaskana, S. alsine, S. borealis, S. calycantha, S. corei, S. crassifolia, S. crispa, S. cuspidata, S. dicranoides, S. fontinalis, S. graminea, S. holostea, S. humifusa, S. irrigua, S. littoralis, S. longifolia, S. longipes, S. media, S. neglecta, S. nitens, S. obtusa, S. pallida, S. palustris, S. parva, S. porsildii, S. pubera, S. ruscifolia, S. umbellata
Synonyms Alsine obtusa, Alsine viridula, Alsine washingtoniana, S. viridula, S. washingtoniana S. dichotoma var. americana, Alsine americana, Arenaria stephaniana var. americana
Name authority Engelmann: Bot. Gaz. 7: 5. (1882) (Porter ex B. L. Robinson) Standley: Contr. U. S. Natl. Herb. 22: 336. (1921)
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