Key to Lathyrus

View taxon page for Lathyrus

(For a list of species in Lathyrus, use the above link.)

Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.

1. Leaflets 2; generally of disturbed habitats

2. Corolla 20–30 mm

3. Inflorescence 4–15-flowered; wings of stem, 

petiole 

Leaf stalk, connecting leaf blade to stem; sometimes more or less indistinct.

often >= 2 mm wide ..... L. latifolius

3' Inflorescence 2–4-flowered; wings of stem, petiole < 2 mm wide

4. Fruit hairy; leaflets 

ovate 

Egg-shaped (i.e., widest below the middle) in two dimensions (i.e., in one plane), as a leaf.

to narrowly 

elliptic 

In the shape of a flattened circle or ellipse; wider than linear

, length 1.2–3 × width ..... L. odoratus

4' Fruit glabrous; leaflets 

lanceolate 

Narrowly elongate, widest in the basal half, often tapered to an acute tip.

to widely ovate, length 1.2–6.5 × width ..... L. tingitanus

2' Corolla 8–15 mm

5. Fruit hairy; inflorescence 1–2-flowered; calyx tube ± = 

lobes 

1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth.

..... L. hirsutus

5' Fruit glabrous; inflorescence 1-flowered; calyx tube ± <= lobes

6. Inflorescence axis not extended beyond flower; calyx tube << lobes; corolla red-purple ..... L. cicera

6' Inflorescence axis extended as bristle beyond flower; calyx tube ± <= lobes; corolla not red-purple

7. Peduncle 2–8 cm; corolla lavender or purple; fruit veins indistinct, netted ..... L. angulatus

7' Peduncle 0.5–2 cm; corolla orange-red; fruit veins distinct, longitudinal ..... L. sphaericus

1' Leaflets 2–16, > 2 at least on some leaves; generally of natural habitats

8. Leaflet, fruit gland-dotted; leaflets ± 14–16 – NCoR (Humboldt, n Mendocino cos.) ..... L. glandulosus

8' Leaflet, fruit not gland-dotted; leaflets often < 14

9. Stem with wings ± >= 1 mm wide

10. Leaflets (4)6(8), 

opposite 

1. Arranged in pairs along an axis - e.g., two leaves per node. 2. Occurring in the same rank, directly above or below, as 'stamens opposite petals'. 3. Located directly across from.

; immediate coast, n NCo ..... L. palustris (2)

10' Leaflets generally 8–16, irregularly arranged; immediate coast only in n CCo

11. Corolla 10–15 mm, white, generally lavender-striate, fading yellow-tan; nw KR (Del Norte, w Siskiyou cos.) ..... L. delnorticus (2)

11' Corolla 15–20 mm, generally pink to pink-purple ..... L. jepsonii

12. Plant generally 

puberulent 

Minutely hairy.

; KR, NCoR, CaR, n SN, GV, CW, SCoRO ..... var. californicus

12' Plant glabrous; GV (especially Solano Co., nearby CCo) ..... var. jepsonii

9' Stem with angles or flanges < 1 mm wide

13. Tendrils not coiled or branched, often a short bristle

14. Stipule ± >= 

leaflet 

A leaf-like unit of a compound leaf; distinguished from a leaf by the absence in its axil of a bud, branch, thorn, or flower; lacking lateral, basal appendages (stipules); either simple (leaf 1-compound, with primary leaflets) or compound (leaf 2-compound, with primary and secondary leaflets; 3-compound, with primary, secondary, and tertiary leaflets, etc).

; generally dunes, beaches of immediate coast – NCo, n&c CCo

15. Plant glabrous or puberulent; leaflet 2.5–4.5 cm ..... L. japonicus (2)

15' Plant gray-hairy; leaflet 1–2 cm ..... L. littoralis

14' Stipule < leaflet; not of immediate coast

16. Inflorescence 1–2-flowered; leaflet generally 0.5–2 cm; fruit glabrous or puberulent

17. Leaflets 10–15, elliptic to ovate, 1–2 cm; fruit puberulent – NCo, NCoR, SnFrB ..... L. torreyi

17' Leaflets 4–8, generally 

oblong 

Longer than wide, with nearly parallel sides; wider than linear.

or narrowly lanceolate to 

linear 

Elongate, with nearly parallel sides; narrower than elliptic or oblong.

; fruit glabrous

18. Leaflets 4, lance-oblong, generally 0.5–1(2) cm; corolla green-white, dark-striate; NCoRH (Red Mtn, Humboldt Co.) ..... L. biflorus

18' Leaflets of at least some leaves 4–8, narrowly lanceolate to linear, 1.5–8 cm; corolla pale lavender to purple; KR, SNH, MP ..... L. lanszwertii var. aridus (2)

16' Inflorescence 2–16-flowered; leaflet 1–8 cm; fruit glabrous

19. Stems 

erect 

Upright; vertically oriented.

, many, clustered; inflorescence dense; corolla white to pink, 17–23 mm; MP (Modoc Co.) ..... L. rigidus

19' Stems erect or sprawling, 1–few, clustered; inflorescence open or dense; corolla lavender to pink-purple or, if white, < 17 mm; n CA-FP

20. Leaflets 10–16, subopposite to 

alternate 

1. Arranged singly, often spirally, along an axis - e.g., one leaf per node. 2. Occurring in different ranks, appearing to be between, not directly above or below, as 'stamens alternate petals'.

; stipules in width often ± = leaflets; plant glabrous – KR, n&c NCoR ..... L. polyphyllus (3)

20' Leaflets 4–10, irregularly arranged or opposite; stipules in width generally ± <= leaflets; plant often hairy

21. Corolla 13–25 mm; leaflets generally elliptic or widely ovate, generally opposite ..... L. nevadensis var. nevadensis (2)

21' Corolla 7–12 mm; leaflets generally linear to lanceolate, irregularly arranged or opposite ..... L. lanszwertii

22. Corolla pale lavender to purple; KR, SNH, MP ..... var. aridus (2)

22' Corolla white to cream, banner often dark-striate; KR, NCoR ..... var. tracyi (2)

13' Tendrils, at least on some leaves, coiled and generally branched

23. Leaflets ± = stipules, 6–8; coastal beaches, dunes – NCo (Del Norte, Humboldt cos.) ..... L. japonicus (2)

23' Leaflets generally > stipules, 6–8 or not; generally inland

24. Corolla white-yellow to bronze-orange (drying tan or dark), 11–14 mm; banner 

reflexed 

Abruptly bent or curved downward or backward.

above middle; inflorescence 10–15-flowered, dense, generally 1-sided – flower appearing wide, blocky; KR, NCoR, SN ..... L. sulphureus

24' Corolla not white-yellow (except Lathyrus lanszwertii var. tracyi) to bronze-orange (occasionally fading tan-yellow), 11–14 mm or not; banner reflexed or bent from middle or below; inflorescence 1–15-flowered, generally ± open (1-sided)

25. Corolla wine-red to crimson, 25–35 mm; banner reflexed 120–180° – s SCo, PR (San Diego Co.) ..... L. splendens

25' Corolla white to purple, 8–25 mm; banner bent ± 90°

26. Leaflets (4)6(8), opposite, glabrous or ± puberulent, flowers 3–6 per inflorescence, 15–20 mm; immediate coast, n NCo ..... L. palustris (2)

26' Leaflets, flowers not entirely as above; immediate coast only in n CCo

27. Stipules > 1 cm wide, leaflets 10–16, plants of KR, NCoR ..... L. polyphyllus (3)

27' Stipules < 1 cm wide and leaflets <= 12 or plants not of KR, NCoR

28. Inflorescence generally 2-flowered; ne DMoj (Grapevine Mtns, Inyo Co.) ..... L. hitchcockianus

28' Inflorescence occasionally 2–16-flowered; not DMoj

29. Corolla white or cream, fading yellow-tan (occasionally to lavender in Lathyrus vestitus var. ochropetalus) – NW

30. Stem flanged or narrowly winged; stipules widely triangular, 0.5–0.8 cm wide; nw KR (Del Norte, w Siskiyou cos.) ..... L. delnorticus (2)

30' Stem angled or ± flanged; stipules generally lanceolate, < 0.5 mm wide; NW

31. Leaflets generally 4–6, glabrous or puberulent; corolla 9–12 mm ..... L. lanszwertii var. tracyi (2)

31' Leaflets generally 8–12, glabrous; corolla 14–16 mm ..... L. vestitus var. ochropetalus

29' Corolla purple, lavender, or ± red (occasionally to white in Lathyrus nevadensis var. nevadensis)

32. Stipules > 1 cm wide; leaflets 10–16 – KR, NCoR ..... L. polyphyllus (3)

32' Stipules < 1 cm wide; leaflets 4–12

33. Flowers often crowded, generally 8–14, corolla 14–20 mm; leaflets 8–12, generally subopposite to alternate; w CA-FP ..... L. vestitus

34. Corolla wine red to dark purple, 16–20 mm; banner generally reflexed > 90°; SCo, s ChI, PR ..... var. alefeldii

34' Corolla pale lavender to purple, 14–18 mm; banner bent ± 90°; NCo, NCoR, CW, SW ..... var. vestitus

33' Flowers generally spaced, either 2–10 and corollas 8–16 mm or 2–4 and corollas 13–25 mm; leaflets 4–10, opposite or subopposite; especially KR, CaR, SN

35. Leaflets generally opposite, generally elliptic or widely ovate; inflorescence 2–4-flowered; corolla 13–25 mm ..... L. nevadensis var. nevadensis (2)

35' Leaflets generally subopposite or irregularly arranged, ovate to linear; inflorescence 2–10-flowered; corolla 8–16 mm

36. Stipules widely ovate-triangular, often toothed, conspicuous; calyx glabrous except lobes often finely 

ciliate 

Having generally straight, conspicuous hairs along margins or edges.

; corolla generally 10–14 mm, banner upcurved above other petals ..... L. brownii

36' Stipules lanceolate, not toothed, often inconspicuous; calyx generally hairy; corolla 10–16 mm, banner generally more reflexed than other petals ..... L. lanszwertii var. lanszwertii

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