Lathyrus latifolius (Fabaceae) Perennial Sweet Pea, Everlasting Pea: Beautiful, Showy, Colorful yet highly Toxic
Warning: This plant is highly toxic. The information presented below is for educational purposes only
Lathyrus latifolius is a plant of considerable beauty and hidden danger. Native to southern and central Europe, this vigorous perennial climber has been cultivated as an ornamental for centuries, valued for its showy pink, purple, or white flowers and its ability to thrive in poor soils. It has escaped cultivation and naturalized across temperate regions worldwide, often persisting along roadsides, railway embankments, and waste ground. Traditional medicine used it sparingly, primarily for external applications, but modern understanding of its chemistry has shifted attention to the neurotoxic amino acid ODAP (β-N-oxalyl-L-α,β-diaminopropionic acid), which it shares with its more notorious relative, the grass pea (Lathyrus sativus). Modern research from 2025 and 2026 is now examining the precise mechanisms of lathyrism, the plant's ecological persistence, and its potential as a genetic resource for developing low-toxin Lathyrus cultivars.
Photographs © Upasana Raj, Portland. Used with permission.
1. Taxonomic Insights
Species: Lathyrus latifolius L.
Family: Fabaceae (Leguminosae, subfamily Papilionoideae)
Genus: Lathyrus
Basionym: Lathyrus latifolius L. (no change; original Linnaean designation)
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Botanical Description
Lathyrus latifolius is a perennial herbaceous climber with a deep, spreading root system and winged stems that scramble or climb by means of branched tendrils. The plant typically reaches 1 to 3 metres in height when supported, forming dense tangles of vegetation. Individual plants may persist for many years, regenerating from a woody rootstock each spring.
Key Identification Features:
The stem is broadly winged, glabrous, and climbing or scrambling. The leaves are alternate, pinnate, with a single pair of leaflets and a branched tendril at the tip. Leaflets are broadly elliptic to lanceolate, 3 to 8 centimetres long and 1 to 3 centimetres wide, with a glaucous, blue-green colour and prominent parallel veins. The stipules are large, ovate to lanceolate, 2 to 5 centimetres long, and half-arrow-shaped at the base. The inflorescence is an axillary raceme bearing 3 to 12 flowers on a long peduncle. Individual flowers are papilionaceous, 2 to 3 centimetres long, with a broad standard petal and wings. Flower colour ranges from deep magenta-pink to purple, occasionally white. The flowers are unscented, unlike those of the annual sweet pea (Lathyrus odoratus). The fruit is a flattened, hairless legume, 5 to 10 centimetres long and 6 to 10 millimetres wide, turning brown at maturity and containing 10 to 15 seeds. Seeds are globular to slightly angular, 4 to 6 millimetres in diameter, and brown or mottled in colour.
Distribution: Native to southern and central Europe, from Portugal east to the Balkans and north to southern Germany. It has been introduced and naturalized throughout temperate North America, South America, Australia, New Zealand, and parts of Asia. It grows from sea level to 1,500 metres elevation.
Conservation Status: Not assessed by the IUCN. The plant is widely cultivated as an ornamental and is considered naturalized rather than threatened in most regions. In some areas, it is classified as invasive.
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Etymology
The generic name Lathyrus derives from the Greek "lathyros," the ancient name for a kind of pea, possibly related to "la," meaning very, and "thyros," meaning passionate or exciting, possibly alluding to the plant's stimulant properties as perceived in antiquity. The specific epithet latifolius comes from the Latin "latus," meaning broad, and "folium," meaning leaf, referring to the broad leaflets that distinguish this species from its narrow-leaved relatives.
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2. Common Names
Scientific Name: Lathyrus latifolius | English: Perennial Sweet Pea, Everlasting Pea, Broad-Leaved Everlasting Pea, Perennial Pea | French: Gesse à larges feuilles, Pois vivace, Gesse vivace | German: Breitblättrige Platterbse, Stauden-Wicke | Spanish: Guisante de olor perenne, Arvejilla silvestre, Látiro de hoja ancha | Italian: Cicerchia a foglie larghe, Pisello odoroso perenne | Portuguese: Ervilha-de-cheiro-perene, Chícharo-de-folha-larga | Dutch: Brede lathyrus, Siererwt | Russian: China shirokolistnaya (Чина широколистная) | Polish: Groszek szerokolistny | Swedish: Rosenvial | Norwegian: Breibladflatbelg | Japanese: Shūkaku endō (宿根エンドウ) | Turkish: Geniş yapraklı mürdümük
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3. Related Herbs from the Fabaceae Family
Lathyrus latifolius belongs to the Fabaceae family, one of the largest and most economically important plant families, containing both valued food crops and species with significant toxicological concerns.
Lathyrus sativus (Grass Pea): The most important species in the genus, cultivated as a food crop in drought-prone regions of Asia and Africa. Contains the neurotoxic amino acid ODAP, responsible for neurolathyrism when consumed in large quantities over extended periods.
Lathyrus odoratus (Sweet Pea): The annual ornamental species, valued for its fragrant flowers. Also contains toxic amino acids and should not be consumed.
Lathyrus sylvestris (Flat Pea): A related perennial species with similar climbing habit and toxicity profile, occasionally used as a forage crop.
Pisum sativum (Garden Pea): A close relative in the same tribe (Fabeae), widely cultivated as a food crop. Lacks the toxic amino acids of Lathyrus species.
Vicia faba (Broad Bean): Another related legume in the tribe Fabeae, consumed as a staple food in many regions, though associated with favism in susceptible individuals.
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4. Medicinal Uses: Summary of Primary and Secondary Actions
Primary Actions (Historical and Preclinical):
None Established: Unlike many of its relatives, Lathyrus latifolius has no well-documented primary medicinal actions. Its historical use was limited and primarily external.
Secondary Actions (Preclinical and Emerging):
Antioxidant: Extracts show moderate free radical scavenging activity in vitro, attributed to phenolic compounds and flavonoids.
Antimicrobial: Preliminary in vitro studies indicate activity against certain bacterial strains, though evidence is limited.
Neurotoxic: The presence of ODAP and related neurotoxic amino acids defines the plant's pharmacological significance, though this is a toxicological rather than therapeutic action.
Allelopathic: The plant produces compounds that may influence the germination and growth of neighbouring species, contributing to its competitive success in disturbed habitats.
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Medicinal Parts
The plant has no established medicinal use in modern practice. Historical use was limited to external applications of the aerial parts.
Aerial Parts: Occasionally used externally as a poultice for minor wounds and skin irritations in some European folk traditions. Not recommended for internal use under any circumstances.
Seeds: Contain the highest concentration of neurotoxic amino acids. Absolutely contraindicated for consumption.
Roots: Not used medicinally.
Flowers: Ornamental only. Not used medicinally.
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5. Phytochemistry
5.1 Neurotoxic Amino Acids
The defining chemical class of Lathyrus species, responsible for their toxicological significance.
β-N-Oxalyl-L-α,β-diaminopropionic Acid (ODAP): The principal neurotoxic amino acid found in Lathyrus species. It is present in all parts of the plant, with highest concentrations in the seeds. ODAP is a structural analogue of glutamate and acts as an excitotoxic agent at glutamate receptors. Chronic consumption leads to neurolathyrism, a degenerative motor neuron disease characterized by spastic paralysis of the lower limbs.
β-Aminopropionitrile (BAPN): A related toxic amino acid found in lower concentrations. It inhibits lysyl oxidase, an enzyme critical for collagen cross-linking, leading to osteolathyrism and angiolathyrism, characterized by skeletal deformities and vascular fragility.
L-α,γ-Diaminobutyric Acid (DABA): Another neurotoxic amino acid present in the genus, with excitotoxic properties similar to ODAP.
5.2 Flavonoids
Quercetin: A flavonoid with antioxidant, anti-inflammatory, and enzyme-inhibitory properties.
Kaempferol: Present in moderate concentrations, contributing to antioxidant activity.
Apigenin: A flavone with anti-inflammatory, antioxidant, and anxiolytic properties.
5.3 Phenolic Acids
Chlorogenic Acid: A phenolic acid with antioxidant, anti-inflammatory, and hepatoprotective properties.
Caffeic Acid: Present in moderate concentrations, contributing to antioxidant activity.
Ferulic Acid: Another phenolic acid with antioxidant and potential antidiabetic effects.
5.4 Other Compounds
Tannins: Condensed tannins are present in moderate amounts, contributing to astringency.
Saponins: Triterpenoid saponins have been detected, though in lower concentrations than in many related legumes.
Proanthocyanidins: Present in the seeds and seed coats, contributing to antioxidant activity and astringency.
Lectins: Proteinaceous compounds with the potential to agglutinate red blood cells, though less studied than in other legume species.
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6. Mechanisms of Action
6.1 Neurotoxicity: Excitotoxic Glutamate Receptor Activation
ODAP is a structural analogue of glutamate, the primary excitatory neurotransmitter in the central nervous system. It binds to and activates AMPA and kainate glutamate receptors, causing excessive calcium influx into neurons. The elevated intracellular calcium triggers a cascade of events including activation of proteases, lipases, and endonucleases, generation of reactive oxygen species, and ultimately neuronal cell death. The motor neurons of the upper spinal cord are particularly vulnerable, leading to the characteristic spastic paraparesis of neurolathyrism. The mechanism requires chronic exposure over weeks to months, and susceptibility is increased by malnutrition, particularly deficiency of sulphur-containing amino acids.
6.2 Osteolathyrism: Lysyl Oxidase Inhibition
β-Aminopropionitrile inhibits lysyl oxidase, a copper-dependent enzyme responsible for the oxidative deamination of lysine residues in collagen and elastin. Without this cross-linking, the structural integrity of connective tissue is compromised. This leads to skeletal deformities, joint laxity, and vascular fragility, collectively known as osteolathyrism and angiolathyrism. These effects are distinct from the neurotoxic effects of ODAP and are more commonly associated with other Lathyrus species, particularly Lathyrus odoratus.
6.3 Antioxidant Activity: Free Radical Scavenging
The flavonoid and phenolic acid content enables the plant to neutralize reactive oxygen species in vitro. These compounds donate hydrogen atoms to free radicals, converting them to less reactive species. The antioxidant activity is moderate and does not offset the toxicological significance of the amino acids.
6.4 Antimicrobial Activity: Membrane Disruption
The phenolic acids and flavonoids disrupt microbial cell membranes and inhibit essential enzymes in vitro. The activity is weak to moderate and not clinically significant.
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7. Traditional and Ethnobotanical Uses
7.1 External Wound Care
Formulation: Fresh plant poultice.
Preparation and Use: The crushed aerial parts were occasionally applied to minor wounds, bruises, and skin irritations in some European folk traditions. The astringent tannins were believed to promote healing.
Scientific Validation: No modern studies support this use. The neurotoxic amino acids may be absorbed through broken skin, making even external use inadvisable.
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7.2 Ornamental Cultivation
The plant has been cultivated as an ornamental since at least the sixteenth century, valued for its showy flowers and vigorous growth. It is a common component of cottage gardens and is used in floral arrangements.
Scientific Validation: Not applicable. This use reflects horticultural rather than medicinal significance.
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7.3 Regional Ethnomedicinal Applications Summary
Europe: Used sparingly and externally for wound care in some folk traditions. The plant was more commonly valued as an ornamental than as a medicine.
North America: Introduced as an ornamental and naturalized widely. No significant medicinal tradition documented.
Australia and New Zealand: Used exclusively as an ornamental species. No medicinal tradition documented.
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8. Healing Recipes, Teas, Decoctions, and Practical Applications
8.1 Cautionary Note on Internal Preparations
No internal preparation of Lathyrus latifolius can be recommended. The neurotoxic amino acid ODAP and related compounds make any infusion, decoction, tincture, or other preparation prepared from this plant unsafe for consumption. Historical recipes involving Lathyrus species should be viewed with extreme caution, as the risks of neurolathyrism and related conditions are well documented.
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8.2 Identification and Avoidance
Purpose: To prevent accidental consumption.
Preparation and Use: Learn to identify Lathyrus latifolius by its winged stems, paired leaflets with tendrils, and showy pink to purple flowers. Do not confuse it with edible peas (Pisum sativum) or other edible legumes. The seeds of Lathyrus species are generally smaller, more angular, and often mottled compared to edible peas.
Scientific Validation: Accurate identification is essential for harm reduction. Misidentification of Lathyrus species as edible legumes has led to documented cases of lathyrism.
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8.3 External Caution
Even external application of the fresh plant is not recommended. The neurotoxic amino acids may be absorbed through damaged skin, and the risk-benefit profile does not favour use. Safer alternatives for wound care are readily available.
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8.4 Culinary Uses and Nutritional Information
Lathyrus latifolius has no culinary use and should not be consumed. The seeds contain neurotoxic amino acids that can cause irreversible neurological damage when consumed over extended periods. The plant should not be confused with garden peas or other edible legumes.
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9. Clinical Significance and Evidence Summary
9.1 Evidence Hierarchy by Activity
Neurotoxicity: Definitive evidence from animal studies, human epidemiological data, and clinical case reports. The mechanism of excitotoxic glutamate receptor activation is well characterized. This is the most clinically significant property of the plant.
Osteolathyrism: Strong evidence from animal studies and some human case reports. The mechanism of lysyl oxidase inhibition is well understood.
Antioxidant: Moderate evidence from in vitro assays. The activity is not clinically significant given the toxicological profile.
Antimicrobial: Limited evidence from in vitro studies. Not clinically significant.
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9.2 Clinical Trial Data
No human clinical trials have been conducted for Lathyrus latifolius for any therapeutic indication. The plant's toxicological profile has excluded it from clinical research.
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9.3 Safety and Toxicology Data
The toxicology of Lathyrus species is well documented. Neurolathyrism, caused by chronic consumption of ODAP-containing seeds, has been described in epidemics in India, Ethiopia, and Bangladesh, primarily associated with Lathyrus sativus consumption during famines. The condition is characterized by spastic paralysis of the lower limbs, with onset typically occurring after two to six months of consumption. Osteolathyrism and angiolathyrism, caused by BAPN, are less common but have been documented in animal studies and occasional human cases. Lathyrus latifolius contains both ODAP and BAPN, though at lower concentrations than Lathyrus sativus.
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10. Safety and Toxicology
10.1 Toxicity Profile
Acute Toxicity: Acute consumption of small quantities is unlikely to produce immediate symptoms. The toxicity of ODAP requires chronic exposure to produce neurological damage.
Chronic Toxicity: Chronic consumption of seeds or other plant parts containing ODAP leads to neurolathyrism, characterized by irreversible spastic paralysis. The condition is progressive and has no effective treatment once established.
Reproductive Toxicity: Animal studies indicate that ODAP and related compounds may have teratogenic and reproductive effects. The plant should be avoided during pregnancy.
10.2 Contraindications and Precautions
Internal Use: Absolutely contraindicated. No part of the plant should be consumed.
Pregnancy and Lactation: Contraindicated in all forms.
Children: Contraindicated. Children are more susceptible to neurotoxic effects.
Malnutrition: Individuals with protein-calorie malnutrition or deficiencies of sulphur-containing amino acids are at elevated risk of lathyrism and should avoid all Lathyrus species.
10.3 Potential Drug Interactions
No drug interactions are documented, as the plant is not used in modern medicine. The neurotoxic amino acids may theoretically interact with glutamatergic medications, but the clinical relevance is minimal given the contraindication against internal use.
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11. Quality Control Parameters
11.1 Marker Compounds for Standardisation
For safety assessment and research purposes, ODAP and BAPN are the primary marker compounds. Total phenolic content may serve as an additional marker for research purposes.
11.2 Recommended Analytical Methods
High-performance liquid chromatography (HPLC) with derivatization or mass spectrometry detection is used for quantification of ODAP and related neurotoxic amino acids. The picrate paper method may be used for rapid screening of cyanide potential, though this is less relevant for Lathyrus than for cyanogenic species.
11.3 Suggested Specifications
There are no therapeutic specifications, as the plant is not used in modern medicine. For research purposes, any material should be clearly labelled with ODAP and BAPN content and handled as a neurotoxic substance.
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12. Cultivation and Sustainability
12.1 Growth Requirements
Climate: Temperate. Prefers cool winters and warm, dry summers.
Habitat: Roadsides, railway embankments, waste ground, and hedgerows. Thrives in open, sunny locations.
Altitude: Grows from sea level to 1,500 metres.
Soil: Prefers well-drained, sandy or loamy soils. Tolerates poor, nutrient-deficient soils and is notable for its drought tolerance once established.
Propagation: By seed and vegetatively through rhizome division. Seeds require scarification for optimal germination.
12.2 Sustainable Harvesting
The plant is not cultivated commercially for medicinal use. It is widely grown as an ornamental and is more commonly managed as a garden plant than harvested for any medicinal purpose.
12.3 Conservation Status
Not threatened. Lathyrus latifolius is widely cultivated and naturalized across temperate regions. It is considered an ornamental asset rather than a conservation concern, though it can be invasive in some natural areas.
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13. Cultivar and Varietal Comparison
Lathyrus latifolius has been cultivated for centuries, with several named cultivars developed for ornamental purposes.
'Pink Pearl': A popular cultivar with soft pink flowers, compact growth, and reduced seed set compared to the wild type.
'White Pearl': A white-flowered cultivar, otherwise similar to 'Pink Pearl'.
'Rosa Perle': A European cultivar with deep rose-pink flowers.
'Albus': A white-flowered form, occasionally found in cultivation.
The species shows moderate morphological variation across its range, with flower colour varying from deep magenta to white. All forms contain the neurotoxic amino acids ODAP and BAPN, regardless of cultivar.
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14. Research Gaps and Future Directions
14.1 Critical Research Gaps
ODAP Biosynthesis: The biosynthetic pathway for ODAP remains incompletely characterized. Understanding the genes and enzymes involved could inform breeding programs for low-toxin Lathyrus cultivars.
Toxicity Thresholds: The precise threshold for neurotoxic effects in humans is not well established, and individual susceptibility factors are poorly understood.
Ecological Role: The role of neurotoxic amino acids in plant defence and stress tolerance requires further investigation.
Comparative Toxicity: Systematic comparison of ODAP and BAPN content across different Lathyrus species and cultivars is incomplete.
14.2 Future Research Priorities
Low-Toxin Breeding: Given the potential of Lathyrus species as drought-tolerant food crops, development of low-ODAP cultivars remains a priority for food security research.
Neuroprotection: Investigation of compounds that might mitigate or prevent ODAP-induced neurotoxicity could inform treatment strategies for lathyrism.
Excitotoxicity Research: ODAP serves as a valuable tool for studying excitotoxic neuronal damage, with implications for understanding motor neuron diseases such as amyotrophic lateral sclerosis.
Ornamental Safety: Development of sterile, low-seed ornamental cultivars could reduce the risk of accidental consumption and limit invasive spread.
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15. Commercial Applications
15.1 Ornamental Horticulture
The primary commercial application of Lathyrus latifolius is ornamental. It is widely grown in gardens for its showy flowers and climbing habit, and is a common component of wildflower mixes and cottage garden plantings.
15.2 Genetic Resource
The species serves as a genetic resource for breeding programs aimed at improving Lathyrus sativus and other related species. Traits such as perennial habit, drought tolerance, and disease resistance are of interest.
15.3 None in Modern Medicine
The plant has no commercial application in modern medicine. Its toxicological profile precludes any use in pharmaceuticals, nutraceuticals, or herbal products.
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16. Related Plants for Further Study
Lathyrus sativus (Grass Pea): The most important species in the genus, cultivated as a food crop in drought-prone regions. Shares the neurotoxic amino acid ODAP and is the primary cause of neurolathyrism.
Lathyrus odoratus (Sweet Pea): The annual ornamental species, valued for its fragrant flowers. Contains similar toxic amino acids.
Pisum sativum (Garden Pea): A close relative in the same tribe, widely cultivated as a food crop. Lacks the toxic amino acids of Lathyrus species.
Vicia faba (Broad Bean): Another related legume in the tribe Fabeae, consumed as a staple food in many regions.
Lens culinaris (Lentil): A related legume in the tribe Fabeae, cultivated as a major food crop worldwide.
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17. Reference Literature
Primary Research
ODAP neurotoxicity review (2018) comprehensively documents the excitotoxic mechanism of ODAP at glutamate receptors and the clinical features of neurolathyrism.
Lathyrism epidemiology study (2015) documents the distribution and risk factors for lathyrism in regions where Lathyrus species are consumed.
ODAP biosynthesis study (2020) investigates the enzymatic pathway for ODAP production in Lathyrus species.
Antioxidant activity study (2024) demonstrates moderate free radical scavenging activity of Lathyrus latifolius extracts in vitro.
Lysyl oxidase inhibition study (2016) characterizes the mechanism of BAPN-induced osteolathyrism and angiolathyrism.
Lathyrus germplasm study (2019) evaluates the genetic diversity and toxin content across Lathyrus species, informing breeding programs.
Key Monographs and Floras
Flora Europaea: Provides comprehensive botanical descriptions and distribution data for the species across Europe.
Flora of North America: Documents the species' naturalization and distribution in North America.
The Jepson Manual: Higher Plants of California: Provides botanical descriptions and distribution data for the species.
Handbook of Legumes of World Economic Importance: Details the species' role in horticulture and agriculture.
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18. Disclaimer
Lathyrus latifolius contains neurotoxic amino acids, particularly ODAP and BAPN, which can cause irreversible neurological damage when consumed. Internal use is absolutely contraindicated. External use is not recommended.
This information is for educational and academic purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
Pregnant or nursing women and children must not use this plant in any form.
Individuals with malnutrition or nutrient deficiencies are at elevated risk of lathyrism and must avoid all Lathyrus species.
Do not confuse Lathyrus latifolius with edible peas or other edible legumes. Accurate identification is essential to prevent accidental poisoning.
Always consult a qualified healthcare practitioner before using any plant for medicinal purposes.
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