Flora of North America species comparison

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Crotalaria

Crotalaria spectabilis

rabbitbells, rattlebox

rattlebox, showy crotalaria, showy rattlebox
Habit Herbs [shrubs], annual or perennial, unarmed; taprooted. Herbs annual.
Stems

erect, ascending, spreading, decumbent, or prostrate, glabrous or pubescent.

suffrutescent basally, erect, 50–150 cm, glabrous.
Leaves

alternate, palmately compound or unifoliolate;

stipules present or absent, usually persistent, filiform to foliaceous;

petiolate or subsessile;

leaflets 1 or 3[–7], stipels absent, blades 5–150 mm, margins entire, surfaces glabrous or pubescent.

unifoliolate;

stipules ovate to ovate-lanceolate, not decurrent on stem, 4–7 mm;

blade obovate to elliptic, 50–150 mm, length 1.5–2.5 times width, surfaces glaucous, strigose abaxially, glabrous-punctate adaxially.
Racemes

12–22-flowered, terminal, subterminal, or lateral, 10–50 cm;

bracts persistent, cordate-auriculate, 5–8 mm.
Inflorescences

(1 or)2–50-flowered, usually terminal or subterminal, leaf-opposed, rarely axillary, racemes [heads or flowers solitary or fascicled];

bracts present, persistent or caducous;

bracteoles present, paired proximal to calyx.

Flowers

papilionaceous;

calyx usually cylindrical, rarely campanulate or cupulate, lobes 5;

corolla usually yellow, sometimes orangish, rarely white, blue, or lavender, glabrous or hairy outside;

stamens 10, monadelphous;

anthers alternately basifixed on long filaments and dorsifixed on small filaments, dehiscing longitudinally;

style with 1 or 2 lines of hairs adaxially;

stigma terminal, usually bilobed.

calyx broadly cylindrical, 10–15 mm, lobes triangular-lanceolate, glabrous;

corolla bright yellow, faintly red-lined, 17–25 mm.
Fruits

legumes, subsessile to long-stipitate, usually inflated, globose, ovoid to ellipsoid, or cylindrical, dehiscent, often tardily so, glabrous or pubescent.

Legumes

30–45 × 10–20 mm, glabrous.
Seeds

1–70, oblique-cordiform to oblong-reniform;

hilar sinus obvious, aril sometimes conspicuous.

x

= 7, 8.

2n

= 16.

Crotalaria

Crotalaria spectabilis
Phenology Flowering (Jan–)Aug–Oct (year-round).
Habitat Grassy or fallow fields, roadsides, ditches, borrow pits, lake edges, disturbed areas.
Elevation 10–200 m. (0–700 ft.)
Distribution
from USDA
United States; Mexico; Central America; South America; West Indies; Europe; Asia; Africa; Indian Ocean Islands; Pacific Islands; tropics and subtropics; mostly eastern and southern tropical Africa [Introduced in Australia]
[BONAP county map]
from FNA
AL; AR; FL; GA; IL; LA; MD; MO; MS; NC; SC; TN; TX; VA; Asia [Introduced in North America; introduced also in Mexico, West Indies, Central America, South America, Indian Ocean Islands (Reúnion), Pacific Islands]
[WildflowerSearch map]
[BONAP county map]
Discussion

Species ca. 600 (15 in the flora).

Crotalaria biflora Linnaeus (native to India) was collected in 1959 as a waif on chrome ore piles in Newport News, Virginia (C. F. Reed 1964). The species is an annual, distinguished as hirsute-villous to subsericeous, stems prostrate, 5–12 cm, leaves sessile, unifoliolate, blades ovate to oblong or oblong-ovate, surfaces villous-hirsute, flowers one or two, on axillary peduncles, and hirsute, ovoid to cylindrical-ovoid legumes.

Crotalaria alata Buchanan-Hamilton ex D. Don (native to Himalayan Asia) was collected in 1939 as an escape in Gainesville, Florida (W. A. Murrill s.n., MO); subsequently, it has not been recorded in the flora area. The species is perennial, distinguished as hirsute to strigose-hirsute, stems erect, 10–20 cm, leaves unifoliolate, blades lanceolate to elliptic-lanceolate or elliptic, stipules decurrent, forming wings on internodes, and apically bilobed, flowers in terminal and axillary racemes, 4–10 cm, and legumes glabrous.

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

In Texas, Crotalaria spectabilis is known from Brazos, Cameron, Karnes, and Liberty counties.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Leaves 3-foliolate.
→ 2
2. Leaflet blades 5–15(–35) mm; legumes 7–20 mm.
→ 3
3. Stems mostly decumbent to prostrate, minutely and sparsely strigillose; legumes.
C. pumila
3. Stems erect to decumbent, loosely strigose to strigose-hirsute; legumes 7–10 mm.
C. virgulata
2. Leaflet blades (10–)20–130(–180) mm; legumes (16–)18–70 mm.
→ 4
4. Leaflet blades linear to linear-lanceolate, elliptic-lanceolate, or lanceolate, lengths 5–10 times widths.
→ 5
5. Racemes 12–26(–40)-flowered; corollas 8–11 mm; legumes 4–6 mm diam.
C. lanceolata
5. Racemes 4–12-flowered; corollas 18–20 mm; legumes (10–)15–20 mm diam.
C. ochroleuca
4. Leaflet blades obovate, ovate, elliptic-obovate, elliptic-oblanceolate, elliptic, elliptic-lanceolate, or spatulate-obovate, lengths 1.3–4.5 times widths.
→ 6
6. Stipules absent; leaflet blades elliptic to elliptic-lanceolate, or elliptic-oblanceolate, 40–100(–140) mm, lengths 3–4.5 times widths; calyces basally truncate and deflexed against pedicels.
C. trichotoma
6. Stipules usually present (persistent or caducous); leaflet blades elliptic, ovate, obovate, elliptic-obovate, or spatulate-obovate, (10–)20–70 mm, lengths 1.3–2.5 times widths; calyces sometimes basally truncate, not deflexed against pedicels.
→ 7
7. Legumes 5–6 mm diam., slightly to conspicuously curved, minutely puber­ulent to glabrate; stems strigose; leaflet surfaces strigillose abaxially, glabrous adaxially.
C. pallida
7. Legumes 10–15 mm diam., straight, villous-hirsute to hispid-hirsute; stems hirsute-villous to strigose-hirsute; leaflet surfaces glabrous or hairy on abaxial midvein.
C. incana
1. Leaves unifoliolate.
→ 8
8. Corollas usually blue to lavender, sometimes white or pale yellow tinged blue; stipules present, often encircling nodes.
C. verrucosa
8. Corollas bright yellow; stipules present and not encircling nodes, or absent.
→ 9
9. Stipules decurrent on mid and distal stems.
→ 10
10. Herbs annual; stems erect to decumbent, hirsute-pilose; leaflet blade lengths 4–8 times widths.
C. sagittalis
10. Herbs perennial; stems decumbent, prostrate, ascending, or erect, strigose or strigose-sericeous to hirsute-villous; leaflet blade lengths 1–12 times widths.
→ 11
11. Leaflet blades linear-lanceolate, linear-oblanceolate, linear, oblong, or elliptic (narrower distally), lengths (2–)4–10 times widths, surfaces glabrous adaxially; stems erect to ascending.
C. purshii
11. Leaflet blades broadly elliptic to elliptic-ovate, ovate, broadly lanceolate, linear, linear-lanceolate, or obovate-oblanceolate, lengths 1–12 times widths, surfaces strigose to strigose-hirsute adaxially; stems prostrate to decumbent or ascending.
C. rotundifolia
9. Stipules, when present, not decurrent on stems.
→ 12
12. Herbs perennial; stipules absent; leaflet blades (5–)8–19 mm; stems 2–10 cm; corollas 8–9 mm.
C. avonensis
12. Herbs annual; stipules usually present; leaflet blades 30–150 mm; stems 30–200(–400) cm; corollas 15–25 mm.
→ 13
13. Stipules ovate to ovate-lanceolate, 4–7 mm; floral bracts 5–8 mm, per­sistent; stems glabrous.
C. spectabilis
13. Stipules, when present, filiform or setaceous, 1–2 mm; floral bracts 2–5 mm, persistent or caducous; stems strigose or strigose-sericeous.
→ 14
14. Leaflet blades obovate to spatulate or oblanceolate, 30–80 mm, lengths.
→ 2
2. 2–3(–4) times widths; stems 30–90 cm.
C. retusa
14. Leaflet blades linear-elliptic to oblong, 50–150 mm, lengths 2.5–4 times widths; stems 100–200(–400) cm.
C. juncea
Source FNA vol. 11. Author: Guy L. Nesom. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae Fabaceae > subfam. Faboideae > Crotalaria
Sibling taxa
C. avonensis, C. incana, C. juncea, C. lanceolata, C. ochroleuca, C. pallida, C. pumila, C. purshii, C. retusa, C. rotundifolia, C. sagittalis, C. trichotoma, C. verrucosa, C. virgulata
Subordinate taxa
C. avonensis, C. incana, C. juncea, C. lanceolata, C. ochroleuca, C. pallida, C. pumila, C. purshii, C. retusa, C. rotundifolia, C. sagittalis, C. spectabilis, C. trichotoma, C. verrucosa, C. virgulata
Synonyms C. retzii
Name authority Linnaeus: Sp. Pl. 2: 714. (1753) — name conserved: Gen. Pl. ed. 5, 320. (1754) — name conserved Roth: Nov. Pl. Sp., 341. (1821)
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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