Lathyrus L.
(incl. Orobus L.)
Lathyrus is a genus of ca. 160 species. Most are native in the northern hemisphere (some also in East-Africa and South-America). About 11 species are generally considered to be native in Belgium, although residence status for several species is quite uncertain. Three species are more or less doubtlessly native: Lathyrus linifolius (Reichard) Bässler, L. palustris L. and L. pratensis L. Lathyrus nissolia L. and L. sylvestris L. are probably originally native in rather few locations but are now increasingly found in man-made, often highly artificial habitats. Lathyrus aphaca L. and L. tuberosus L. are at most archaeophytes. Lathyrus hirsutus L. was long considered to be merely adventitious (Lawalrée 1963) but is nowadays accepted as native, at least in parts of Belgium (Lambinon & Verloove 2012). Finally, Lathyrus japonicus Willd., native in large parts of western Europe, is exceptionally seen as an ephemeral, potentially native species along the Belgian coast.
Lathyrus is an economically important genus. Many species are cultivated as ornamentals (see Hibberd 1995, Jäger & al. 2008 for an overview of the genus in cultivation in Europe), for green manure or as fodder plants. Several others are weeds of arable land.
The generic limits of Lathyrus are now more or less established. Orobus, formerly accepted as a genus of its own, is included in Lathyrus. Morphologically it is obviously closely related to Vicia. Most species of Lathyrus are distinguished by parallel leaf venation (and often winged stems) but one section is only separated by style-pubescence (Mabberley 2008). Molecular studies support Kupicha’s (1983) classification (Kenicer & al. 2005).
Additional information on the genus Lathyrus is available at “The sweet pea and Lathyrus species information site” at www.lathyrus.info.
1. Corolla yellowish (rarely orangish yellow) === 2
1. Corolla pinkish, purplish, bluish, reddish or white, never yellowish === 4
2. Stem winged, at least above. Annual (easily uprooted) === 3
2. Stem unwinged. Perennial or annual (native) === L. aphaca and L. pratensis
3. Leaflets 1-paired, the upper linear to linear-lanceolate. Corolla yellow to orangish. Seeds 7-8, papillose to tuberculate === L. annuus
3. Leaflets 1-2-paired, the upper ovate. Corolla pale yellow. Seeds 5-7, smooth === L. ochrus
4. Leaves without tendrils === 5
4. At least the uppermost leaves with tendrils === 9
5. Annual. Leaves reduced to a single blade. Inflorescence 1-2-flowered (native) === L. nissolia
5. Perennial. Leaves with at least one pair of leaflets. Inflorescence 2-12-flowered === 6
6. Stem and petiole winged (native) === L. linifolius
6. Stem and petiole unwinged (at most angled) === 7
7. Stipules ovate-triangular, at least 8 mm wide. Confined to coastal habitats (native) === L. japonicus p.p.
7. Stipules lanceolate, up to 8 mm wide. Garden escapes in woods, old parks, etc. === 8
8. Leaflets (1-) 2-4 pairs, long acuminate at apex, 3-7 cm long. Stipules ovate-hastate, 2-8 mm wide. Plant not blackish when dry. Pods with 8-14 seeds === L. vernus
8. Leaflets (3-) 4-6 pairs, obtuse to mucronate at apex, 1-4 cm long. Stipules linear, 1-2 mm wide. Plant turning blackish when dry. Pods with 6-10 seeds === L. niger
9. At least the upper leaves with more than one pair of leaflets (native) === L. japonicus p.p. and L. palustris
9. Leaflets with one pair of leaflets === 10
10. Stem not winged (native) === L. tuberosus
10. Stem winged === 11
11. Inflorescence with (3-) 5-15 flowers. Perennial === 12
11. Inflorescence with 1-3 (-4) flowers. Annual === 14
12. Calyx teeth (sub-) equal, all shorter than the tube. Peduncle ca. as long as subtending leaf. Corolla with standard usually pink suffused greenish. Leaves acute at apex (gradually tapering), without or with indistinct cross-veins (native) === L. sylvestris
12. Calyx teeth markedly unequal, the lower much exceeding calyx tube length. Peduncle much longer than the subtending leaf. Corolla more uniformly coloured, pinkish-purple or magenta. Leaves rounded at apex (abruptly tapering), usually with distinct cross-veins === 13
13. Corolla ca. 15-20 mm long, pinkish-purple. Mature leaves usually more than 4x as long as wide. Petioles (incl. wings) usually narrower than the stems. Stipules up to 8 mm wide === L. heterophyllus
13. Corolla ca. 20-30 mm long, magenta. Mature leaves usually less than 4x as long as wide. Petioles (incl. wings) usually at least as wide as stems. Stipules up to 15 mm wide === L. latifolius
14. Plant pubescent, at least in part. Inflorescence 1-3(-4)-flowered === 15
14. Plant glabrous. Flowers solitary === 16
15. Longest peduncles > 70 mm long. Corolla 20-35 mm long, purple, pinkish or white === L. odoratus
15. All peduncles much shorter. Corolla 8-15 mm long, purple with blue wings (native) === L. hirsutus
16. Peduncle 30-60 mm long. Corolla 12-24 mm long. Pod 10-18 mm wide with 2 distinct wings === L. sativus
16. Peduncle 10-30 mm long. Corolla 5-15 (-20) mm long. Pod 5-10 mm wide, at most keeled (not winged) === L. cicera
Additional aliens: Lathyrus angulatus L. (Medit., vector unknown), L. clymenum L. (Medit., wool alien), L. inconspicuus L. (Medit., W-As., wool alien) and L. sphaericus Retz. (Euras., N-Afr., vector unknown).
Literature:
Allkin R. (1985) The geographical distribution of Lathyrus, Vicieae Database Project (Univ. Southampton) 6: 1-35.
Asmussen C . & Liston A. (1998). Chloroplast DNA characters, phylogeny and classification of Lathyrus (Fabaceae). Am. Journ. Bot. 85: 387-401. [available online at: www.amjbot.org/content/85/3/387.full.pdf]
Ball P.W. (1968a) Flora Europaea Notulae Systematicae ad Floram Europaeum Spectantes No. 7. Short notulae. Feddes Repert. 79: 34-68.
Ball P.W. (1968b) Lathyrus. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 2. Cambridge University Press, Cambridge: 136-143.
Baggott C.D. (1997) A herbarium-based ecogeographic survey of the genus Lathyrus section Lathyrus: 122 p.
Bässler M. (1966) Die Stellung des Subgenus Orobus (L.) Baker in der Gattung Lathyrus L. und seine systematische Gliederung. Feddes Repert. 72: 69-97.
Bässler M. (1973) Revision der eurasiatischen Arten von Lathyrus L. sect. Orobus (L.) Gr. et Godr. Feddes Repert. 84: 329-447.
Bässler M. (1981) Revision von Lathyrus L. Sect. Lathyrostylis (Griseb.) Bässler (Fabaceae). Feddes Repert. 92: 179-254.
Çildir H. (2011) Morphology, anatomy and systematics of the genus Lathyrus L. (Leguminosae) in Central Anatolia, Turkey. PhD thesis [available online at: https://etd.lib.metu.edu.tr/upload/12613432/index.pdf]
Gams H. (1924) Lathryrus. In: Hegi G. (ed.), Illustrierte Flora von Mitteleuropa, IV. Band 3, Teil 2. München, Lehmann: 1562-1609.
Gluch W. (1971) Wuchformstudien an zentraleuropäischen Fabaceen. 4. Die Stauden der Gattungen Lathyrus L. und Vicia L. Feddes Repert. 81: 539-575.
Hibberd F.K. (1995) Lathyrus. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 4. Cambridge University Press, Cambridge: 518-521.
Jäger E.J. & Werner K. (eds.) (2005) Rothmaler Band 4. Exkursionsflora von Deutschland. Gefässpflanzen: Kritischer Band. Springer Verlag, Berlin: 880 p.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Kenicer G. (2008) An introduction to the genus Lathyrus L. Curtis’s Bot. Mag. 25(4): 286-295.
Kenicer G.J., Kajita T., Pennington R.T. & Murata J. (2005) Systematics and biogeography of Lathyrus (Leguminosae) based on internal transcribed spacer and cpDNA sequence data. Am. Journ. Bot. 92: 1199-1209.
Kupicha F. (1983) The infrageneric structure of Lathyrus. Notes Roy. Bot. Gard. Edinburgh 41: 209-244.
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Lawalrée A (1963) Papilionaceae. In: Robyns W. (ed.), Flore Générale de Belgique, vol. 4, fasc. 2. Jardin Botanique de l’Etat, Bruxelles: 135-228.
Leht M. (2009) Phylogeny of Old World Lathyrus L. (Fabaceae) based on morphological data. Feddes Repert. 120(1-2): 59-74.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Parsons R. (2013) Perennial Lathyrus. The Plantsman N.S. 12(3): 178-183.
Shehadeh A.A. (2011) Ecogeographic, genetic and taxonomic studies of the genus Lathyrus L. PhD thesis, university of Birmingham [available online at: http://etheses.bham.ac.uk/3061/1/Shehadeh11PhD.pdf]
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.