Crocanthemum dumosum

E. P. Bicknell

Bull. Torrey Bot. Club 40: 613. 1913.

Common names: Bushy rockrose or frostweed
Endemic
Synonyms: Helianthemum dumosum (E. P. Bicknell) Fernald
Treatment appears in FNA Volume 6. Treatment on page 404. Mentioned on page 401, 403, 405.

Herbs, cespitose, sometimes moundlike. Stems ascending to divergent, usually red-tinged, 10–20 (–30) cm, stellate-pubescent. Leaves cauline; petiole 1–2 mm; blade usually elliptic, rarely oblanceolate, 10–20 (–26) × 3–7 (–10) mm, tapered to base, apex acute, surfaces stellate-tomentose and with simple hairs abaxially, dull, stellate-pubescent and with simple and, sometimes, glandular-hairs adaxially, lateral-veins raised abaxially. Inflorescences terminal or subterminal, cymes; chasmogamous flowers 1–3 per cyme, cleistogamous 1 (–2) per glomerule, on lateral leafy branches 6–18 cm, flowering 1–3 months later than chasmogamous. Pedicels 2.4–6 mm, with stellate, simple, and glandular-hairs; bracts absent. Chasmogamous flowers: outer sepals lanceolate, 2–6 × 0.8–3 mm, inner sepals 7–10 × 4—-6.5 mm, apex acute; petals obovate, 8–15 × 5–13 mm; capsules 4–7 × 3–4 mm, glabrous. Cleistogamous flowers: outer sepals rudimentary, knoblike to triangular and acute, 0.4–1 × 0.3–0.6 mm, inner sepals ovate, 3–6 × 2.5–3.2 mm, apex acute; capsules 3.2–4.5 × 2.5–3.2 mm, glabrous.


Phenology: Flowering late May–Jun.
Habitat: Sandplain grasslands, maritime heathlands
Elevation: 0–50 m

Discussion

Crocanthemum dumosum occurs in nine coastal counties. Crocanthemum dumosum and C. canadense are closely related; the former inhabits specialized, maritime environments. They can be distinguished in the field by the ascending or divaricate, relatively numerous stems of C. dumosum, often giving it a bushy aspect (versus erect, single or relatively few stems, and nonbushy); leaf surfaces dull under dense stellate hairs in C. dumosum (versus lustrous under sparser stellate hairs). Identification of occasional plants may be equivocal; those are a small minority.

Using AFLP markers, S. G. Obae et al. (2013) found that Crocanthemum dumosum nested within the same cluster as C. canadense. The authors “recommend that it be considered as a subspecific variant of C. canadense,” but did not make a new combination. Additional molecular work warranted to solidify their findings.

Selected References

None.

Lower Taxa

None.
... more about "Crocanthemum dumosum"
Bruce A. Sorrie +
E. P. Bicknell +
2 cm20 mm <br />0.02 m <br /> (2.6 cm26 mm <br />0.026 m <br />) +
0.7 cm7 mm <br />0.007 m <br /> (1 cm10 mm <br />0.01 m <br />) +
1 cm10 mm <br />0.01 m <br /> (2 cm20 mm <br />0.02 m <br />) +
tapered +  and oblanceolate +
0.3 cm3 mm <br />0.003 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
0.32 cm3.2 mm <br />0.0032 m <br /> (0.45 cm4.5 mm <br />0.0045 m <br />) +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.32 cm3.2 mm <br />0.0032 m <br />) +
Bushy rockrose or frostweed +
Conn. +, Mass. +, N.Y. +  and R.I. +
0–50 m +
connate +  and distinct +
later than chasmogamous +
cleistogamous +  and chasmogamous +
loculicidal +
Sandplain grasslands, maritime heathlands +
umbellate +, thyrsiform +  and cymose +
racemose +, paniculate +  and corymbose +
subterminal +  and terminal +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.32 cm3.2 mm <br />0.0032 m <br />) +
6 cm60 mm <br />0.06 m <br /> (18 cm180 mm <br />0.18 m <br />) +
stipulate +  and estipulate +
whorled +, opposite +  and alternate +
undulate +  and revolute +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
acute;knoblike;triangular +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (?) +  and 0.06 cm0.6 mm <br />6.0e-4 m <br /> (?) +
6-12-carpellate +, 5-carpellate +, 3-carpellate +  and 2-carpellate +
crassinucellate +  and bitegmic +
orthotropous +
0.24 cm2.4 mm <br />0.0024 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
crumpled +  and imbricate +
yellow +, white +, red +, purple +, pink +, dark red +  and green +
distinct +
8mm;15mm +
obovate +
0.5 cm5 mm <br />0.005 m <br /> (1.3 cm13 mm <br />0.013 m <br />) +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
Flowering late May–Jun. +
Bull. Torrey Bot. Club +
persistent +
20 cm200 mm <br />0.2 m <br /> (30 cm300 mm <br />0.3 m <br />) +
red-tinged +
not dimorphic +
stellate-pubescent +
10 cm100 mm <br />0.1 m <br /> (20 cm200 mm <br />0.2 m <br />) +
3 +  and 1 +
sessile +  and petiolate +
stellate-pubescent +  and stellate-tomentose +
Helianthemum dumosum +
Crocanthemum dumosum +
Crocanthemum +
species +
herb +  and cespitose +