Singletary Pea

Lathyrus hirsutus

Fabaceae (Legume family)


Singletary pea is a legume with winged stems that grow from 10 to 40 inches long. Its compound leaves have two long, narrow leaflets up to 3 inches long and terminate in a branched tendril. The small, pea-like flowers are red to bluish. Distinctive pods, 1 to 1.5 inches long, are covered with hair attached to small, raised bumps. Each pod contains four to 10 mottled, round seeds.


Historically, singletary pea was planted as a cover crop and a cool season forage, often mixed with small grains. It has escaped cultivation and is found in north central and northeastern Texas. It is common along roadsides and in pastures where it has been allowed to go to seed.

Toxic Agent

The vegetation of singletary pea is not toxic and is highly nutritious, but the seeds contain toxic amino acids. Lathyrism, the neurological syndrome most often produced by chronic consumption of the seeds, can affect all species including humans, but horses are the most sensitive. Horses are usually affected by hay containing intact pods with seeds. Bovine cases usually result from grazing pastures with many mature plants.

Signs of Livestock Ingestion

Horses with lathyrism demonstrate these signs: Incoordination of rear legs; Unusual stance with rear legs too far forward; Exaggerated stepping of rear legs; Paralysis of rear legs.

Cattle with lathyrism show: Reluctance to stand; Incoordination of rear legs; Inability to rise

Chronic consumption of seeds of other Lathyrus species result in skeletal deformities in growing animals. Calves born to cows that have consumed seeds of singletary pea for several months during gestation may have crooked legs and a curved spine.

Management Strategies

Remove horses from hay containing singletary pea seeds as soon as signs develop; most will recover within 4 to 6 weeks. The condition becomes irreversible if the animals continue to eat the seeds. Cattle removed from the pasture recover in a few days. Pastures with singletary pea should be grazed before seed production. Do not feed hay containing seedpods to horses.