Lathyrus
pea, peavine, sweet-pea, vetchling, wild pea
erect, sprawling, or climbing, angled and/or winged, glabrous or pubescent.
alternate, even-pinnate (phyllodic in L. nissolia);
stipules present, foliose, base usually semisagittate, rarely sagittate or hastate;
rachis sometimes winged, usually terminated in simple or branched, prehensile tendril, sometimes reduced to bristle or absent;
petiolate;
leaflets (0 or)2–18, paired or unpaired, usually decreasing in size distally, stipels absent, blades 5–150 mm, margins entire, usually with several longitudinal veins in addition to midrib, surfaces glabrous or sparsely to densely pubescent.
1–20-flowered, axillary (terminal in L. pusillus), racemes or flowers solitary, erect or lax;
bracts absent;
bracteoles absent.
papilionaceous;
calyx symmetric or obliquely campanulate, without gibbous base, 5–12 mm, lobes 5, equal or unequal, when unequal, abaxial lobes short and triangular, lateral and keel lobes longer and lanceolate or linear;
corolla white, cream, yellow, pink, lavender, lilac, rose, red, reddish orange, crimson, blue to purple, violet, magenta, or bicolored, wings and keel often lighter than banner, 6–30 mm;
petal clawed, distinct from blade;
stamens 10, diadelphous;
anthers dorsifixed, uniform;
style abaxially compressed, sometimes twisted, laterally pubescent.
legumes, usually sessile, rarely stipitate, flattened or terete, linear, dehiscent, non-septate, usually with obscure margins, splitting along both margins, glabrous or sparsely pubescent;
valves twisted after dehiscence.
3–15, usually dull brown, black, tan, or dark green, often mottled, spherical, sometimes angular.
= 7 (polyploidy rare).
Lathyrus
Species ca. 150 (41 in the flora).
F. K. Kupicha (1983) separated Lathyrus into 13 sections worldwide; about three-fourths of the members are perennials and one-fourth are annuals. All perennial North American species are included in sect. Orobus (Linnaeus) Godron, which contains about one-third of all Lathyrus species. The single native annual species, L. pusillus, has been assigned to sect. Notolathyrus Kupicha, a section perhaps closely allied to Orobus species in North America (C. B. Amussen and A. Liston 1998). Lathyrus is predominantly diploid with 2n = 14. Chromosome counts have been reported for 20 of the 29 species native to North America (S. L. Broich 1989). There has been no worldwide treatment of the genus at the species level. Lathyrus in North America was last revised by C. L. Hitchcock (1952) and summarized by D. Isely (1998).
Recent phylogenetic studies have placed Lathyrus consistently within the Vicieae (M. F. Wojciechowski et al. 2004); subgeneric relationships have yet to be resolved (C. B. Amussen and A. Liston 1998; G. J. Kenicer et al. 2005; H. Schaefer et al. 2012).
Twelve of the 41 Lathyrus species treated herein have been introduced to North America and have become locally established to widely naturalized. Deliberate introductions include species used as ornamentals, cover, and green manure and cover crops. One native species, L. pusillus, has been developed as a winter cover crop; a second native species, L. splendens, has been cultivated as an ornamental.
A number of native Lathyrus are polymorphic and include one or more of the following: glabrous and pubescent races, variation in stature and habit from short-stemmed and erect to long-stemmed and sprawling or climbing, variation in tendril morphology from bristles to well developed and branched, variable leaflet number, ovate and linear leafleted races, and variation in flower color and size. Within some polymorphic species, morphological variation is such that distinct varieties can be delimited. Within other species, however distinctive some populations may be, intergradation among forms is such that well-marked taxa cannot be reliably described.
Although probably cultivated where possible in North America and occasionally escaping, Lathyrus sativus Linnaeus and L. niger (Linnaeus) Bernhardi are not treated here.
Diets that include large quantities of flour made from seed of several Lathyrus species (primarily L. sativus, L. cicera Linnaeus, and L. clymenum Linnaeus) are known to produce lathyrism, a paralytic syndrome in humans and livestock (A. D. Kaul and D. Combes 1986). In humans, lathyrism has been associated historically with poverty or drought that force populations to rely on Lathyrus seed for consumption.
Unless otherwise noted in the taxon description: stipules are semisagittate; leaf rachises are not winged; styles are flattened perpendicular to the ovary axis and not rotated; legumes are sessile, without winged abaxial sutures, and are not prominently veined; vestiture, if reported present, consists of unicellular, eglandular trichomes; the number of leaflets and tendril morphology are for distal stem leaves bearing inflorescences; leaflet dimensions given are for basal leaflets on the rachis of leaves subtending inflorescences; flower lengths reported are the distance from the base of the calyx tube to the distal keel petal margin; references to the relationship between calyx lobe length and calyx tube length always take into account the longest lobe present; wing and keel petals are almost always lighter in color than the banner petal and colors given in descriptions are for the most pigmented part of the corolla. Distributions of introduced species are approximate.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaflets 0 or 2. | → 2 |
2. Leaflets 0. | → 3 |
3. Stipules ovate, base hastate; leaf rachises reduced to branched or unbranched tendrils; corollas yellow. | L. aphaca |
3. Stipules filiform-linear, base semisagittate; tendrils absent, leaves phyllodic, grasslike; corollas crimson. | L. nissolia |
2. Leaflets 2. | → 4 |
4. Herbs perennial; inflorescences 4–15-flowered. | → 5 |
5. Corollas yellow. | L. pratensis |
5. Corollas reddish, purple, magenta, pink, or white. | → 6 |
6. Stems not winged; ovaries glabrous. | L. tuberosus |
6. Stems broadly winged; ovaries glandular-pubescent. | → 7 |
7. Stipules 7–15 mm wide, at least 1/2 width of stem. | L. latifolius |
7. Stipules 1–3 mm wide, less than 1/2 width of stem. | L. sylvestris |
4. Herbs annual; inflorescences 1–3(or 4)-flowered. | → 8 |
8. Stems not winged; inflorescences extending beyond terminal flower in a bristle. | → 9 |
9. Inflorescences 2–7 cm; legumes with indistinct reticulate venation. | L. angulatus |
9. Inflorescences 1–2 cm; legumes with prominent longitudinal venation. | L. sphaericus |
8. Stems narrowly to broadly winged; inflorescences with a terminal flower. | → 10 |
10. Ovaries densely pustulose-based pubescent. | → 11 |
11. Flowers 20–25 mm. | L. odoratus |
11. Flowers 8–10 mm. | L. hirsutus |
10. Ovaries glabrous. | → 12 |
12. Leaf rachis not winged; flowers 7–10 mm. | L. pusillus |
12. Leaf rachis winged (as the stem); flowers 10–30 mm. | → 13 |
13. Flowers 20–30 mm; lateral calyx lobes deltate, usually shorter than tube. | L. tingitanus |
13. Flowers 10–12 mm; lateral calyx lobes linear-triangular, much longer than tube. | L. cicera |
1. Leaflets (2–)4–18. | → 14 |
14. Tendrils often absent or reduced to bristles, not well developed. | → 15 |
15. Leaflet blades obovate to oblanceolate, surfaces densely villous; corollas dark purple; coastal sand dunes, deflation plains along Pacific Coast from c California northward to British Columbia. | L. littoralis |
15. Leaflet blades usually linear, lanceolate, or ovate, rarely obovate, surfaces not densely villous; corollas blue-purple, lilac, pinkish, violet, magenta, or cream to white; not coastal. | → 16 |
16. Corollas white or cream. | → 17 |
17. Inflorescences 5–15-flowered; n California. | L. tracyi |
17. Inflorescences 1–6-flowered; w North America. | → 18 |
18. Stipules much smaller than distal leaflets. | → 19 |
19. Flowers 7–15 mm; inflorescences 2–5 cm; Arizona, California, Colorado, Nevada, New Mexico, c Oregon, Utah, c Washington, Wyoming. | L. lanszwertii |
19. Flowers 18–22 mm; inflorescences 3–15 cm; ne Oregon, se Washington, adjacent Idaho. | L. nevadensis |
18. Stipules equal to distal leaflets. | → 20 |
20. Flowers 7–8 mm; leaflet blades finely villous; Humboldt County, California. | L. biflorus |
20. Flowers 12–18 mm; leaflet blades glabrous; California, Nevada, Oregon, adjacent Idaho. | L. rigidus |
16. Corollas usually blue-purple, sometimes violet to magenta, lavender, or pinkish. | → 21 |
21. Flowers 8–12 mm. | → 22 |
22. Leaflets 2–4, blades 20–50 mm; British Columbia, n Idaho, w Montana, e Washington. | L. lanszwertii |
22. Leaflets 8–16, blades 5–15 mm; coastal forests of California, Oregon, Washington. | L. torreyi |
21. Flowers 13–20 mm. | → 23 |
23. Leaflets usually scattered; legumes sessile. | → 24 |
24. Leaflets 6–12; n Arizona, sw Colorado, s Idaho, Nevada, nw New Mexico, Utah. | L. brachycalyx |
24. Leaflets 4 or 6; n California, Oregon, Washington. | L. nevadensis |
23. Leaflets usually paired; legumes stipitate. | → 25 |
25. Leaflets 8–12; flowers 16–22 mm; Great Plains and e slopes of Rocky Mountains. | L. decaphyllus |
25. Leaflets 4–8; flowers 12–18 mm; California, Idaho, Nevada, Oregon. | → 26 |
26. Stipules much smaller than distal leaflets; Elko County, Nevada. | L. grimesii |
26. Stipules equal to distal leaflets; e Oregon, adjacent w Idaho, ne California, nw Nevada. | L. rigidus |
14. Tendrils well developed, often branched. | → 27 |
27. Stipules sagittate; lake and ocean shores in North America, ca. 38–70o N latitude. | L. japonicus |
27. Stipules semisagittate; not of coastal shores, sometimes coastal wetlands. | → 28 |
28. Corollas usually white, cream-white, or yellow-cream, rarely light pink or lavender. | → 29 |
29. Corollas orange to yellow-cream, banner blade shorter than claw; California Central Valley and adjacent foothills, northward to sw Oregon. | L. sulphureus |
29. Corollas white or cream-white (sometimes light pink or lavender in L. laetivirens); banner blade equal to or longer than claw; distribution widespread. | → 30 |
30. Leaflets usually paired. | → 31 |
31. Leaflets (5 or)6(–8), stipules somewhat foliose, sometimes equal to distal leaflets; n North America (sw Alaska to Washington, eastward to Atlantic coast). | L. ochroleucus |
31. Leaflets 4–10, stipules much smaller than leaflets; nw California southeastward to New Mexico. | → 32 |
32. Tendrils well developed, often branched; Arizona, Colorado, Nevada, New Mexico, Utah. | L. laetivirens |
32. Tendrils 0–3 cm, usually not branched; n California. | L. tracyi |
30. Leaflets usually scattered (paired in L. hitchcockianus, L. palustris). | → 33 |
33. Stems narrowly winged. | → 34 |
34. Stipules sometimes equal to distal leaflets; nw California, adjacent Oregon. | L. delnorticus |
34. Stipules much smaller than distal leaflets; w California, Oregon, Washington. | → 35 |
35. Lateral calyx lobes lanceolate, (wider distal to base); stems basally branched; coastal ranges of n California, w Oregon, Washington. | L. vestitus |
35. Lateral calyx lobes linear-triangular; stems often branched mid stem (at or just proximal to flowering nodes); Willamette Valley, Oregon, Washington. | L. holochlorus |
33. Stems angled but not winged. | → 36 |
36. Inflorescences 2–6-flowered; Colorado, Utah, Wyoming. | L. lanszwertii |
36. Inflorescences (2–)5–20-flowered; Arizona, California, Idaho, New Mexico, Oregon, Texas, Washington. | → 37 |
37. Lateral calyx lobes lanceolate (wider distal to base); coastal ranges of n California, Oregon, Washington. | L. vestitus |
37. Lateral calyx lobes deltate or linear-triangular; Arizona, Idaho, New Mexico, Oregon, Texas, Washington. | → 38 |
38. Leaflet blades usually linear, rarely lanceolate; Arizona, New Mexico, w Texas. | L. graminifolius |
38. Leaflet blades ovate to lanceolate; Idaho, Oregon, Washington. | → 39 |
39. Stems branched from base or unbranched; Idaho. | L. nevadensis |
39. Stems often branched mid stem (at or just proximal to flowering nodes); Oregon, Washington. | L. holochlorus |
28. Corollas pink, lavender, rose, blue to purple, or deep red. | → 40 |
40. Stems narrowly to broadly winged. | → 41 |
41. Leaflets 14–18, blade surfaces: both with eglandular trichomes, glandular-pubescent abaxially; Humboldt and n Mendocino counties, California. | L. glandulosus |
41. Leaflets 4–12, blade surfaces glabrous, glabrate, or eglandular-pubescent; ne North America, coastal marshes along Pacific Coast of Oregon northward, or coastal mountains of w California from Humboldt County southward to Monterey County. | → 42 |
42. Leaflets 4–8, paired; ovaries glandular-pubescent; ne, e, midwestern North America and coastal marshes along Pacific Coast from California northward. | L. palustris |
42. Leaflets 8–12, scattered; ovaries glabrous; c, n California from Monterey County northward to Humboldt County eastward through Central Valley. | L. jepsonii |
40. Stems angled but not winged. | → 43 |
43. Leaflets 4 or 6, paired; flowers 8–10 mm; Grapevine Mountains of Inyo County, California and adjacent Nye County, Nevada. | L. hitchcockianus |
43. Leaflets (2–)6–16, scattered; flowers (7–)10–30 mm; distribution widespread. | → 44 |
44. Flowers 16–30 mm, corollas deep wine red, banners reflexed toward calyx tube; sw California. | → 45 |
45. Flowers 16–25 mm. | L. vestitus |
45. Flowers 25–30 mm. | L. splendens |
44. Flowers (7–)10–20(–25) mm, corollas lavender, pink, or blue to purple, banners erect; distribution widespread. | → 46 |
46. Leaflets 10–16; stipules nearly equal to distal leaflets. | L. polyphyllus |
46. Leaflets 4–10(–14); stipules much smaller than leaflets. | → 47 |
47. Wings longer than keel (by 1–4 mm). | → 48 |
48. Inflorescences 3–4 cm, 2–4-flowered; ne California, adjacent Nevada and Oregon. | L. brownii |
48. Inflorescences 5–18 cm, 4–13-flowered; sw Colorado, Idaho, ne Oregon, Utah, e Washington. | L. pauciflorus |
47. Wings equal to keel. | → 49 |
49. Corollas white to blue-orchid; leaflet blades usually linear, rarely lanceolate; stems sometimes branched at flowering nodes; inflorescences 10–18 cm; Arizona, New Mexico, w Texas. | L. graminifolius |
49. Corollas rose, lavender, or blue-purple; leaflet blades usually ovate to lanceolate or elliptic, rarely linear; stems usually basally branched; inflorescences 2–10(–25) cm; distribution widespread. | → 50 |
50. Legumes short-stipitate; inflorescences 2–4-flowered; flowers 18–20 mm; Arizona, Colorado, New Mexico, w Texas, se Utah, Wyoming. | L. eucosmus |
50. Legumes sessile; inflorescences 2–20-flowered; flowers (7–)10–18(–20) mm; distribution north and west or eastern United States. | → 51 |
51. Inflorescences 5–20-flowered. | → 52 |
52. Stipules of distal leaves usually less than 1/4 width of distal leaflets; central and eastern North America. | L. venosus |
52. Stipules on distal leaves usually more than 1/4 width of distal leaflets; coastal mountains of California into sw Oregon. | L. vestitus |
51. Inflorescences 2–6-flowered. | → 53 |
53. Banner deeply cordate; n Arizona, sw Colorado, e Nevada, nw New Mexico, w, se Utah. | L. brachycalyx |
53. Banner retuse to shallowly cordate; coastal ranges of California, northward to British Columbia, Great Basin. | → 54 |
54. Flowers 10–15 mm; leaflet blades usually lanceolate, rarely linear; ne California, w Nevada, c Idaho, e Oregon, ne Utah, se Washington. | L. lanszwertii |
54. Flowers 13–18 mm; leaflet blades ovate to lanceolate; coastal ranges of California northward to British Columbia. | L. nevadensis |
CA
OR
WA
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
