A “bitter pea” plant refers to species within the Daviesia genus, part of the Fabaceae (pea) family. Predominantly native to Australia, these plants are characterized by their distinct pea-shaped flowers and often bitter-tasting foliage. The common name “bitter pea” highlights this taste, historically leading some species to be used as a substitute for hops in brewing.
Identifying Bitter Pea
Bitter pea plants are identified by several physical characteristics. They typically grow as slender, erect, or spreading shrubs, 1 to 3 meters tall, though some reach 5 meters. Many species, such as Hop Bitter-pea (Daviesia latifolia) and Gorse Bitter-pea (Daviesia ulicifolia), have broad, dull green “leaves” (often modified stems called phyllodes) that can be elliptic, egg-shaped, lance-shaped, sharply pointed, or have wavy edges with prominent veins.
Their showy, pea-shaped flowers have five petals (a standard, two wings, and a keel) and are usually orange-yellow with dark reddish or maroon markings, often called “eggs and bacon” colors. Borne in clusters in leaf axils, some varieties are fragrant. After flowering (late winter to early summer or September to December), plants produce flattened, triangular pods with one or two seeds.
Habitat and Growth
Endemic to Australia, bitter pea species are widely distributed, primarily in Western Australia. They thrive in dry sclerophyll communities, woodlands, and open forests as understory plants, also found in heathlands, grasslands, or disturbed sites, showing their adaptability.
They prefer well-drained soils but adapt to various types, including clay, skeletal, or sandy. Tolerant of frost and full sun, many are remarkably drought-tolerant, needing minimal water once established. Their nitrogen-fixing ability through root nodules also aids their success in diverse environments.
Toxicity and Safety Concerns
The term “bitter pea” primarily refers to the taste of plants in the Daviesia genus, rather than indicating a specific toxicity concern. Historically, some Daviesia “leaves” were used medicinally or as a hops substitute due to their bitterness. While Daviesia species are not generally reported as acutely toxic, it is important to distinguish them from other “pea” plants, particularly those in the Lathyrus genus, commonly known as sweet peas or vetch peas.
Lathyrus species, like Lathyrus sativus or Lathyrus odoratus (common sweet pea), contain toxic amino acids and nitriles (lathyrogens). Ingesting large quantities can cause lathyrism in humans and animals, leading to neurological problems like weakness, difficulty moving limbs, paralysis, and neural damage. Musculoskeletal issues, including bone pain, abnormal gait, and blood vessel abnormalities, may also occur.
Horses, rodents, turkeys, and sheep are susceptible to Lathyrus poisoning. If ingestion of a suspected toxic Lathyrus plant occurs, seek immediate medical or veterinary attention. While common sweet pea (Lathyrus odoratus) is mildly toxic and serious poisoning is rare due to its bitter taste, vigilance is advised, especially with curious children and pets.
Ecological Impact and Management
Bitter pea plants contribute to Australian ecosystems. As Fabaceae members, they fix atmospheric nitrogen into the soil via root nodules, improving fertility. Their flowers provide pollen and nectar for native insects and birds, and some species offer habitat and shelter for wildlife.
Many Daviesia species are not widely cultivated but are grown by enthusiasts for ornamental value, attractive foliage, and showy flowers. They can be used as garden screens or windbreaks. Propagation is often from scarified seeds to break dormancy. While not invasive, they regenerate naturally from seed or suckers, especially after fire. Management involves well-drained soil and adequate sunlight, as they are low-maintenance once established.