Flora of North America species comparison

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Crocanthemum scoparium

Crocanthemum nashii

Bisbee Peak rushrose, broom rushrose, peak rockrose, peak rush-rose

Florida scrub frostweed or sunrose
Habit Subshrubs. Herbs.
Stems

spreading to erect-fastigiate, 10–45 cm, usually sparsely stellate-pubescent to glabrate, sometimes densely lanate.

from caudices and horizontal rootstocks, erect to ascending, 20–35(–41) cm, stellate-pubescent.
Leaves

cauline, tending to be deciduous in summer;

petiole 0–2 mm;

blade linear, 5–11 × 0.5–2(–3.5) mm, surfaces stellate-pubescent to glabrate abaxially, sparsely stellate-pubescent to glabrate adaxially, lateral veins obscure abaxially.

cauline;

petiole 1–2(–3) mm;

blade oblanceolate-elliptic to lanceolate-elliptic, 15–30(–38) × 3–6(–8.4) mm, surfaces stellate-tomentose, without simple hairs, lateral veins slightly to moderately raised abaxially.
Inflorescences

terminal, panicles or racemes; chasmogamous flowers 1–18 per panicle or raceme, cleistogamous 0.

terminal, thyrses; chasmogamous flowers 1–8 per thyrse, cleistogamous 8–40 per thyrse, flowering 1–3 months later than chasmogamous.
Pedicels

2–6 mm, sparsely or not glandular-hairy;

bracts 2–4 × 0.3–0.5 mm.

3–8(–10) mm;

bracts linear-lanceolate, 1–3.2 × 0.2–0.6 mm.
Chasmogamous

flowers: outer sepals linear, 1.5–3.5 × 0.3 mm, inner sepals 3.5–5(–7.5) × 2–3 mm, apex acute to acuminate;

calyx stellate-pubescent, hairs to 1 mm;

petals obovate, 3–6 × 3–5 mm;

capsules 2.8–3.8 × 2–2.5 mm, glabrous.

flowers: outer sepals linear, 1–3 × 0.3 mm, inner sepals ovate-elliptic, 3.5–5 × 2.7–3.7 mm, apex acute;

petals broadly cuneate, 6–9.5 × 3–6.5 mm;

capsules 2-valved, 3–4.8 × 2.4–3.8 mm, stellate-pubescent distally.
Cleistogamous

flowers: outer sepals linear, 0.5–1.2 × 0.5 mm, inner sepals ovate-elliptic, 1–3.4 × 1–2.3 mm, apex acute;

capsules 2-valved, 3–4 × 2.4–3.5 mm, stellate-pubescent distally.

Crocanthemum scoparium

Crocanthemum nashii
Phenology Flowering Mar–Jun.
Habitat Xeric sand-pine scrub and oak scrub, on stable maritime dunes, on inland sandhills
Elevation 0–100 m (0–300 ft)
Distribution
from FNA
CA; nw Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
FL; NC
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

Even with the recognition of Crocanthemum aldersonii and C. suffrutescens as separate species, morphological diversity within C. scoparium still remains considerable. The two varieties here recognized show differences in habit, average plant height, number of flowers, and distribution. Another variant occurs sporadically along the coast and on Santa Cruz Island, from Monterey to San Diego counties; vegetative parts (at least distal branches, pedicels, and sepals) are covered with white, lanate hairs. This variant has never been formally named. Another form from coastal Mendocino County was called “Helianthemum mendocinensis” by Alice Eastwood on a specimen (H. E. Brown 785, JEPS); the name was never published. These plants have densely stellate-pubescent stems and exceptionally elongate sepal tips.

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

Crocanthemum nashii and C. arenicola are the only species in Crocanthemum with stellate-pubescent ovaries and capsules; C. nashii is unique in having two-valved capsules. It was discovered in New Hanover County, North Carolina, in 1997, disjunct some 540 km from the northernmost Florida populations. The uniformly gray-green foliage, thyrsoid inflorescence, and often patch-forming habit render it unmistakable within its range. Plants with simple hairs mixed with stellate hairs on the calyx were named Helianthemum thyrsoideum.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Stems mostly 10–30 cm, divaricate and spreading or curved proximally and erect distally; mostly near-coastal.
var. scoparium
1. Stems usually 30–45 cm, usually erect-fastigiate, sometimes curved proximally and erect distally; mostly inland.
var. vulgare
Source FNA vol. 6, p. 407. FNA vol. 6, p. 406.
Parent taxa Cistaceae > Crocanthemum Cistaceae > Crocanthemum
Sibling taxa
C. aldersonii, C. arenicola, C. bicknellii, C. canadense, C. carolinianum, C. corymbosum, C. dumosum, C. georgianum, C. glomeratum, C. greenei, C. nashii, C. propinquum, C. rosmarinifolium, C. suffrutescens
C. aldersonii, C. arenicola, C. bicknellii, C. canadense, C. carolinianum, C. corymbosum, C. dumosum, C. georgianum, C. glomeratum, C. greenei, C. propinquum, C. rosmarinifolium, C. scoparium, C. suffrutescens
Subordinate taxa
C. scoparium var. scoparium, C. scoparium var. vulgare
Synonyms Helianthemum scoparium Helianthemum nashii, H. thyrsoideum
Name authority (Nuttall) Millspaugh: Publ. Field Mus. Nat. Hist., Bot. Ser. 5: 175. (1923) (Britton) Barnhart: in J. K. Small, Man. S.E. Fl., 879. (1933)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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