Name: Lathyrus latifolius L.
Family: Fabaceae (the pea family)
Common Names: Perennial Pea (1), Everlasting Pea (2), Broad-leaved Everlasting Pea (3).
Etymology: Lathyrus comes from Lathyros, a leguminous plant of Ancient Greece classified by Theophrastus and believed to be an aphrodisiac. “The name is often said to be composed of the prefix, la, very, and thuros, passionate.” (1). Latifolius means broad-leaved (4).
Botanical synonyms: Lathyrus latifolius L. var. splendens Groenl. & Rumper (5)
Quick Notable Features:
¬ Winged stem and petioles
¬ Leaves with only 2 leaflets
¬ Branched leaf-tip tendril
¬ Pink papilionaceous corolla (butterfly-like)
Plant Height: Stem height usually reaching 2 m (7).
Lathyrus latifolius f. albiflorus Moldenke
L. latifolius f. lanceolatus Freyn (5, 6):
Most Likely Confused with: Other species in the genus Lathyrus, but most closely resembles L. sylvestris (2). May also possibly be confused with species of the genera Vicia and Pisum.
Habitat Preference: A non-native species that has been naturalized along roadsides and in waste areas (7).
Geographic Distribution in Michigan: L. latifolius is scattered throughout Michigan, in both the Upper and Lower Peninsula. In the Upper Peninsula it is found in Baraga, Gogebic, Houghton, Keweenaw, Mackinac, Marquette, Ontonagon, and Schoolcraft counties. In the Lower Peninsula it is found in the following counties: Alpena, Antrim, Benzie, Berrien, Calhoun, Cass, Charlevoix, Cheboygan, Clinton, Emmet, Genesee, Hillsdale, Isabella, Kalamazoo, Kalkaska, Kent, Leelanau, Lenawee, Livingston, Monroe, Montmorency, Newaygo, Oakland, Oceana, Ostego, Saginaw, Sanilac, Van Buren, Washtenaw, and Wayne (2, 5). At least one quarter of the county records are newly recorded since 1985: 29 county records were present in 1985 and there are 38 county-level records as of 2014.
Known Elevational Distribution: Recorded in Utah at elevations between 1,360 and 1,690m (8). It is also recorded in California at elevations generally below 2000m (9).
Complete Geographic Distribution: Native to Europe and North Africa, L. latifolius escaped from cultivation in the United States, and has been naturalized in every state except Alaska, Florida, and North Dakota (2, 5).
Vegetative Plant Description: An herbaceous perennial with stems and petioles that appear to be folded longitudinally. The stems and petioles are actually flanked on two sides by broad wings, 5-10 mm wide. At the base of the petiole are two leafy stipules with basal lobes, 3-5mm long. The glabrous leaves are composed of two leaflets that point upward, each with 3-5 veins originating at the base. The leaflets are lanceolate, elliptic, or oblong, 4-9 cm long and 1-3cm wide (7, 10, pers. obs.). The roots are composed of a taproot plus rhizomes.
Climbing Mechanism: The species climbs using branched leaf-tip tendrils that emerge from between the two leaflets (7). These tendrils are modified leaflets, most likely.
Flower Description: Inflorescences are axillary racemes consisting of 4-14 odorless, purplish-pink or white flowers. The peduncles are generally long, from 10-20cm. The pedicels are also relatively long, 8-15mm, and bear the glabrous green, bell-shaped calyx. The lobes of the calyx are unequal, varying from 5-6mm, and have acuminate or acute tips. The corolla is papilionaceous (papilio is Latin for butterfly) – a bilaterally symmetrical structure composed of a broadly erect banner petal, and a lower keel enclosed by two wing petals. The lower keel is composed of two petals that are fused together, enclosing 10 stamens. The stamens are fused into two groups (diadelphous) – 9 stamens in one group and one stamen free. The pistil consists of a single style and stigma, and a superior ovary. The style is compressed and pubescent, and the ovary is 1-locular (7, 9, 10, 11, 12, 13, 14).
Flowering Time: In the southeastern United States, L. latifolius blooms from May to S
eptember. In the northeastern United States, L. latifolius blooms from June to August (7, 10).
Pollinator: “A diverse group of insects visit the flowers to obtain nectar, but the flowers are effectively pollinated only by pollen-collecting bumblebees, which must force the keel petals open to contact the stamens” (16).
Fruit Type and Description: The fruit of L. latifolius is a 10-25 seeded flat, dehiscent legume: a pea-pod that opens on both sides. The legume is glabrous, 6-10cm long and 7-10mm wide (1, 7, 10). The fruit opens as the dried carpel walls twist.
Seed Description: Seeds are dark in color, 3-5mm in diameter, spherical to tuberculate to oblong, smooth or dimpled (1, 11, pers.obs.).
Dispersal Syndrome: Fruits dehisce violently, scattering the seed contents. Seeds do not exhibit any specialized means of dispersal such as wings or hairs, but appear to roll away from their source populations, establishing themselves not too far downhill from a cultivated population. In addition to sexual reproduction, L. latifolius also invests in vegetative reproduction by rhizomes and stolons (11, 15, 16).
Distinguished by: L. japonicus, L. ochrolucus, L. venosus, and L. palustris are distinguishable from L. latifolius by having 4-12 leaflets instead of only 2. L. pratensis and L. tuberosus do not have winged stems and petioles. L. odoratus and L. hirsutus have a pubescent fruit, whereas L. latifolius has a glabrous fruit. L. sylvestris is very similar to L. latifolius, but can be distinguished by its smaller flower and having only 3-6 flowers per inflorescence (1, 2, 15). Lathyrus species can all be distinguished from Pisum because Pisum bears very large stipules that are larger than the basal leaflets. L. latifolius can be distinguished from Vicia species because L. latifolius has only two leaflets.
Other members of the family in Michigan: Amorpha (2), Amphicarpaea (1), Anthyllis (1), Apios (1), Astragalus (3), Baptisia (4), Caragana (1), Cercis (1), Chamaecrista (2), Cladrasis (1), Colutea (1), Crotalaria (1), Cytisus (1), Dalea (1), Desmodium (12), Genista (1), Gleditsia (1), Glycine (1), Gymnocladus (1), Hedysarum (1), Kummerowia (1), Lathyrus (9), Lespedeza (13), Lotus (1), Lupinus (2), Melilotus (2), Mimosa (1), Orbexilum (1), Phaseolus (2), Pisum (1), Pueraria (1), Robinia (3), Securigera (1), Senna (1), Strophostyles (1), Tephrosia (1), Trifolium (9), Vicia (8), Vigna (1), Wisteria (1) (2, 5).
Ethnobotanical Uses: The seeds of L. latifolius are poisonous to mammals. Lathyrism is a neurological disease caused by eating the seeds of certain species within the genus Lathyrus genus (6, 13). “Lathyrus latifolius was found to be highly toxic, causing convulsions and death. Symptoms appear when the seeds become a major part of the animal’s diet, typically greater than 25 percent for a period of days or weeds. The seeds cause paralysis, skeletal deformity, birth defects, and, if the diet remains unaltered, death” (11,13).
Phylogenetic Information: Fabaceae belongs to the order Fabales, which is closely related to Fagales, Cucurbitales, and Rosales within the clade, Eurosids I. Within Fabaceae, L. latifolius belongs to the subfamily, Faboideae (also known as Papilionoideae). Members of this subfamily are characterized by the papilionaceous flowers. L. latifolius is included in the Fabaceous tribe Fabeae (also known as Vicieae and thus close to the genus Vicia) (6, 12).
Interesting Quotation or Other Interesting Factoid not inserted above
“Members of the genus Lathyrus have caused many cases of illness and death in humans and livestock over the centuries in Europe, Russia, India, and northern Africa. Livestock become poisoned when the seeds mature on forage vines and become a significant part of the animals diet. Human poisoning from L. sativus rarely found wild in the US has occurred during times of drought and famine when people have relied on the seeds as a major food source” (13). Seeds reportedly have a neuroactive amino acid which should be avoided (17)
Literature and websites used:
- Fernald, M.L. 1970. Gray’s Manual of Botany, 8th edition. New York, New York: America Book Company.
- Voss, E.G. 1985. Michigan Flora, Part II Dicots. Bloomfield Hills, MI: Cranbrook Institute of Science.
- Stace, C.A. 1999. Field Flora of The British Isles. Cambridge, England: Cambridge University Press.
- Bailey, L.H. 1963. How Plants Get Their Names. New York, New York: Dover Publications.
- USDA Natural Resources Conservation Service Plant Database. http://plants.usda.gov/java/profile?symbol=LALA4
- USDA Germplasm Resources Information Network. http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?21580
- Radford, A.E., H.E. Ahles, & C.R. Bell 1968. Manual of the Vascular Flora of the Carolinas. Chapel Hill, North Carolina, USA: University of North Carolina Press.
- Digital Atlas of the Vascular Plants of Utah http://earth.gis.usu.edu/plants/index.html
- Jepson Flora Project http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?3691,3922,3940
- Gleason, H.A. & A.R. Cronquist 1991. Manual of Vascular Plants of Northeastern United States and adjacent Canada, 2nd edition. New York City, New York, USA: The New York Botanical Garden.
- Hilty, J. 2002-2006. Weedy Wildflowers of Illinois. Last modified: 03-26-07. http://www.illinoiswildflowers.info/weeds/plants/everlasting_pea.htm
- Stevens, P.F. 2001 onwards. Angiosperm Phylogeny Website. Version 7, May 2006. http://www.mobot.org/MOBOT/research/APweb/welcome.html
- Tull, D. 1999. Edible and Useful Plants of Texas and the Southwest. Austin, Texas, USA: University of Texas Press.
- Bergen, J.Y. 1901. Bergen’s Botany; Key and Flora. Boston, Massachusetts, USA: Ginn and Company.
- Hossaert, M., & M. Valero 1988. Effect of ovule position in the pod on patterns of seed formation in two species of Lathyrus (Leguminosae: Paplinoideae). American Journal of Botany 75(11):1714-1731.
- Godt, M.J.W. & J.L. Hamrick 1991. Genetic variation in Lathyrus latifolius (Leguminosae) American Journal of Botany 78(9):1163-1171.
- Ressler, C. P. A. Redstone, & R.H. Erenberg 1961.Isolation and Identification of a neuroactive Factor from Lathyrus latifolius. Science 134(3473):188-190.
Image Credits (all used with permission):
1) Image of L. latifolius plant retrieved from the Cal Photos website (http://calphotos.berkeley.edu) and Copyright © 2005 Julie Wakelin
2) The picture of the stem was found at the Vanderbilt Bioimages website (www.cas.vanderbilt.edu/bioimages) and the 2003 copyright belongs to Steven J. Baskauf.
3) Image of leaf undersurface © Robyn J. Burnham
4) Photograph of the flowers retrieved from the Cal Photos website (http://calphotos.berkeley.edu) and taken by Louis-M. Landry.
5) Picture of L. latifolius seeds taken by Steve Hurst and retrieved from the U. S. Department of Agriculture via the USDA PLANTS Website (www.plants.usda.gov)
6) Species distribution map, derived from the Michigan Flora Online.
Primary Authors: Michelle Medley and John Bradtke, editing by Robyn J. Burnham, image search by Bradley H. Sisson
© Robyn J. Burnham, University of Michigan
For additional information on Michigan Plant Diversity web pages please contact Robyn J. Burnham via email: rburnham“at”umich.edu