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buck-bean, false-lupine, golden-banner, golden-pea, thermopsis

ashleaf goldenbanner

Habit Herbs, perennial, unarmed, usually rhizomatous. Herbs delicate, 5–10 dm, glabrate to sparsely puberulent.
Stems

erect, ascending, or spreading, glabrate to pubescent.

slender, erect, clustered, many-branched, from single, woody rootstock;

branches spreading at 45–80º, strongly zigzag.

Leaves

alternate, odd-pinnate;

stipules present, usually persistent, ± foliaceous, dimorphic, proximalmost amplexicaul, scarious, and not blade-bearing, distal ones smaller and narrower, subtending leaves;

petiolate;

leaflets 3, stipels absent, subpetiolulate, blade margins entire, not glandular-punctate, surfaces glabrous or pubescent.

stipules sometimes persistent, lanceolate to narrowly ovate, 1–3.5 × 0.3–0.8 cm, base cuneate, apex acuminate;

petiole 1.6–3 cm;

leaflet blades elliptic, 4.5–8 × 2–3.5 cm, lateral veins 9–12 pairs, conspicuously net-veined abaxially, apex acute to acuminate, surfaces glabrous or sparsely puberulent.

Racemes

terminal or lateral, scattered, 12–25 cm;

flowers 7–25-flowered.

Inflorescences

5–90-flowered, usually terminal, sometimes lateral, racemes;

bracts present, deciduous or persistent, apex acute to acuminate;

bracteoles absent.

Peduncles

2.5–5.5 cm;

bracts persistent, lanceolate, 8–12 × 1–3 mm.

Pedicels

7–17 mm, glabrate.

Flowers

papilionaceous;

calyx campanulate, lobes 5, appearing 4-lobed, subequal, abaxial lobes deltate to lanceolate, adaxial lobe double, broader, slightly longer, apex truncate to emarginate;

corolla yellow, banner widely ovate, shorter than wing and keel petals, apex usually cleft, sometimes emarginate or short-mucronate, claw cuneate to oblong, replicate to reflexed, wings not adnate to keel, often asymmetric, auriculate, ± length of keel, claw narrowly oblong, keel petals usually asymmetric, auriculate, posteriorly fused, without beak, claw narrowly oblong;

stamens 10, distinct, uniform;

anthers dorsifixed;

ovary short-stipitate, oblong, usually longer than style, pubescent, velutinous, villous, or tomentose [villosulous];

style glabrous;

stigma minute.

1.6–1.9 cm;

calyx 7–9 × 4–5 mm at limb, lobes 2–3 mm, much shorter than tube;

wing petals elliptic to asymmetrically oblong-elliptic, keel petals asymmetrically oblong-elliptic;

ovary appressed-pubescent;

ovules (6–)12–16.

Fruits

legumes, persistent, stipitate, stipe 2–4 mm, erect, ascending, or divergent, tan to brown, laterally compressed, straight, arcuate, or, rarely, annular, narrowly elliptic, margins straight, or sinuate or lomentaceous from ovule abortion, papery, not elastic, slowly dehiscent, valves separating from apex through both sutures, sericeous, tomentose, velutinous, villous, glabrate, villosulous, or pubescent.

Legumes

irregularly divergent, straight, (3–)5.5–7.5 × 0.3–0.5 cm, inconspicuously appressed-pubescent.

Seeds

1–16, oblong, elliptic, or reniform; often with minute, membranous rim-aril.

(5–)10–15, brown, reniform, 4 × 2.5 mm, short-beaked.

x

= 9.

2n

= 18.

Thermopsis

Thermopsis fraxinifolia

Phenology Flowering (Apr–)May–Jul.
Habitat Rich woodlands, upper hillsides along streams, lower elevations along flood­plains.
Elevation (300–)700–1600 m. ((1000–)2300–5200 ft.)
Distribution
from USDA
North America; Asia
[BONAP county map]
from FNA
AL; GA; NC; SC; TN
[BONAP county map]
Discussion

Species 23 (10 in the flora).

Thermia Nuttall is an illegitimate name that pertains here.

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

Thermopsis fraxinifolia is partially sympatric with T. mollis; in regions of overlap T. fraxinifolia usually occurs at higher elevations along upper slopes of mountainous ridges and hills of the Appalachians. The plant may also occur at lower elevations on alluvial deposits along at least some of the rivers in this region.

Thermopsis fraxinifolia can be distinguished from T. mollis by its more robust and more branching habit, lateral (as well as terminal) inflorescences, and relatively longer pedicels. Furthermore, T. mollis propagates by extensive, vigorous rhizomes, which are absent in T. fraxinifolia.

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

Key
1. Stipules 0.3–0.8 cm wide, base cuneate, not cordate or clasping.
→ 2
2. Stems from single, woody rootstock; pedicels glabrate, 7–17 mm, at least as long as bracts; legumes inconspicuously appressed-pubescent; racemes terminal or lateral; plants montane, (300–)700–1600 m.
T. fraxinifolia
2. Stems from extensive rhizomes; pedicels villosulous, 4–6 mm, shorter than bracts; legumes densely appressed-pubescent; racemes terminal; plants mostly of piedmont, 300–800 m.
T. mollis
1. Stipules 0.5–6 cm wide, base cordate and/or amplexicaul, sometimes acute.
→ 3
3. Legumes ascending or erect.
→ 4
4. Leaflet blade surfaces densely pubescent; seeds 1–7(–10); stipules 0.7–6 cm wide.
→ 5
5. Herbs (2.5–)3–8(–9) dm; stems slender, from rhizomes; racemes 7–30(–35) cm, 10–40-flowered; legumes ascending; widespread in California.
T. californica
5. Herbs 12–23 dm; stems thick, from woody rootstock; racemes 25–60 cm, 30–90-flowered; legumes erect; Santa Ynez Mountains, California.
T. macrophylla
4. Leaflet blade surfaces sparsely pubescent or glabrous; seeds 6–16; stipules 0.7–2.5 cm wide.
→ 6
6. Herbs 2–8(–10) dm; stems slender; pedicels 3.5–5 mm; calyx 9–11 mm, lobes 3–5 mm; Rocky Mountains northwest to Washington and Oregon coast, Newfoundland and Quebec.
T. montana
6. Herbs 6–18 dm; stems thick; pedicels 2–3 mm; calyx 7–8 mm, lobes 2–3 mm; e, se United States.
T. villosa
3. Legumes divergent.
→ 7
7. Herbs 1.2–3 dm; leaflets 1.7–3.3 × 0.6–2 cm, lateral veins 5–7 pairs; peduncles 1–4 cm; legumes strongly arcuate to annular.
T. rhombifolia
7. Herbs 3–18 dm; leaflets 3–11 × (0.5–)2–6.5 cm, lateral veins 6–12 pairs; peduncles 3–10(–11) cm; legumes straight or arcuate.
→ 8
8. Herbs 8–18 dm; stems thick; leaflet blades 6.5–11 × 2.5–6.5 cm, surfaces tomentose; flowers 1.6–1.8 cm; legumes densely tomentose; Humboldt and Siskiyou counties, California.
T. robusta
8. Herbs 3–8(–9) dm; stems slender; leaflet blades 3–7(–8) × 0.5–3.2 cm, surfaces glabrous or glabrate to puberulent; flowers 2–2.9 cm; legumes inconspicuously pubescent; n California to Yamhill County, Oregon, n, e Rocky Mountains, adjacent Great Plains.
→ 9
9. Branches ascending, weakly to moderately or strongly zigzag; leaflet blades 0.5–2.5 cm wide, apex not emarginate; petioles 1–2.5 cm; legumes usually arcuate or annular, sometimes straight; n, e Rocky Mountains, adjacent Great Plains.
T. divaricarpa
9. Branches spreading, moderately to strongly zigzag; leaflet blades 2–3.2 cm wide, apex sometimes emarginate; petioles 2.5–4(–5) cm; legumes straight; n California, w Oregon.
T. gracilis
Source FNA vol. 11. Author: Billie L. Turner†. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae Fabaceae > subfam. Faboideae > Thermopsis
Sibling taxa
T. californica, T. divaricarpa, T. gracilis, T. macrophylla, T. mollis, T. montana, T. rhombifolia, T. robusta, T. villosa
Subordinate taxa
T. californica, T. divaricarpa, T. fraxinifolia, T. gracilis, T. macrophylla, T. mollis, T. montana, T. rhombifolia, T. robusta, T. villosa
Synonyms Drepilia, Scolobus Baptisia fraxinifolia, T. mollis var. fraxinifolia
Name authority R. Brown in W. Aiton and W. T. Aiton: Hortus Kew. 3: 3. (1811) (Nuttall) M. A. Curtis: Amer. J. Sci. Arts 44: 81. (1843)
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