The Ornamental Sweet Pea: Beautiful but Poisonous
The most common and significant example of a non-edible pea is the ornamental sweet pea ($Lathyrus$ $odoratus$). While celebrated for its vibrant flowers and delightful fragrance, all parts of this plant, particularly the seeds, are toxic to humans and animals. It is a frequent source of confusion because the ornamental plant is often mistaken for its edible counterpart, the garden pea ($Pisum$ $sativum$). The distinction is critical for anyone who enjoys gardening or has pets and children who might encounter the plant.
The primary danger in the seeds of the sweet pea plant is the presence of toxic amino acids called lathyrogens. When ingested in large quantities over a prolonged period, these toxins can lead to a serious medical condition known as lathyrism. Lathyrism can cause severe neurological and musculoskeletal issues, though accidental, small-quantity ingestion is less likely to cause a major problem. Still, any amount should be avoided.
Edible Peas: The Safe Varieties
In contrast to the toxic sweet pea, the following pea varieties are safe for consumption and are a staple in many home gardens and kitchens:
- Garden or English Peas ($Pisum$ $sativum$): These are the most common peas that require shelling before eating. The pods are not typically consumed.
- Snow Peas ($Pisum$ $sativum$ var. macrocarpon): The pods of snow peas are edible and are often used in stir-fries. They are flat with small, immature seeds inside.
- Snap Peas ($Pisum$ $sativum$ var. saccharatum): A hybrid of English and snow peas, snap peas have plump, crunchy, edible pods with full-sized, sweet peas inside.
All edible peas belong to the Pisum genus, which is a different botanical family from the toxic Lathyrus genus.
How to Identify Non-Edible Sweet Peas
Learning to distinguish between the poisonous ornamental sweet pea and the edible garden pea is the most important step for garden safety. While their flowers may look similar, there are several key differences to look for.
Visual differences between ornamental and edible pea plants:
- Flowers: Ornamental sweet peas are bred for their vibrant, often pastel-colored, and highly fragrant flowers. Edible peas, while they do flower, have smaller, less showy blooms that are typically white or pale purple.
- Stems: Edible pea stems are round and generally succulent. In contrast, ornamental sweet pea stems are slightly flattened, winged, and rougher in texture.
- Pods: Ornamental sweet pea pods are grey-green, shorter, skinnier, and furry. Edible pea pods are broader, longer, shiny, and bright green.
- Leaves: The leaves of ornamental sweet peas tend to be smaller than those of edible peas.
The Dangers of Lathyrism
Prolonged, high-volume ingestion of sweet pea seeds, or those of other Lathyrus species like the grass pea ($Lathyrus$ $sativus$), can cause a severe paralytic syndrome known as lathyrism. This condition affects the central nervous system and can cause symptoms like weakness, tremors, and in severe cases, paralysis below the knees. The risk is generally highest in populations where toxic peas are a major part of the diet due to famine or poverty. While mild accidental ingestion is unlikely to cause such severe effects, all toxic peas should be treated with caution.
Comparison Table: Ornamental vs. Edible Peas
| Feature | Ornamental Sweet Pea ($Lathyrus$ $odoratus$) | Edible Garden Pea ($Pisum$ $sativum$) |
|---|---|---|
| Genus | Lathyrus | Pisum |
| Edibility | Toxic, inedible | Edible (pods or seeds depending on variety) |
| Primary Use | Ornamental, fragrant flowers | Culinary, vegetable |
| Stems | Winged, flattened, rough | Round, succulent |
| Flowers | Large, showy, often pastel colors | Smaller, less prominent, often white |
| Pods | Furry, shorter, grey-green | Shiny, broader, bright green |
| Seeds | Poisonous | Safe to eat |
Beyond Sweet Peas: Other Non-Edible Pea-Like Plants
While the ornamental sweet pea is the most common toxic variety confused with edible types, other members of the Lathyrus genus should also be treated with caution. Examples include the everlasting pea ($Lathyrus$ $latifolius$), which is also poisonous. There are also wild peas and vetch that, while sometimes eaten, are not ideal for consumption and can be mistaken for edible varieties. Always err on the side of caution and rely on positive identification rather than assuming a plant is safe based on its resemblance to an edible pea.
Safely Distinguishing Edible from Non-Edible Peas
For gardeners, the most reliable method for ensuring safety is proper labeling. Always buy seeds or seedlings from reputable sources and keep track of what you plant. Avoid planting ornamental sweet peas in the same area as your vegetable garden to prevent confusion. If you have any doubt about a plant's identity, especially if it is volunteer growth, do not consume it. Remember that wild peas can also be dangerous, and some members of the Lathyrus genus are very hardy. For definitive identification, consult a knowledgeable horticulturist or a reliable online plant database like the one at Cornell University's Department of Animal Science.
Conclusion: Prioritize Identification for Garden Safety
Ultimately, understanding what peas are not edible is crucial for garden safety. The key distinction lies between the poisonous Lathyrus genus, which includes the ornamental sweet pea, and the edible Pisum genus, which encompasses garden, snow, and snap peas. By paying close attention to botanical characteristics like stem shape, flowers, and pods, you can easily tell the difference and prevent accidental poisoning. When in doubt, always discard the unknown plant. Your vigilance in proper identification is the best defense against garden hazards and ensures a safe, enjoyable harvesting season for your family and pets.
Optional Outbound Link
For more detailed information on poisonous plants, including sweet peas, consult the Cornell University Poisonous Plants Database. This is an authoritative resource for identifying toxic species.
Optional Outbound Link
For detailed information on sweet pea toxicity, including the effects on animals and humans, visit the Cornell University Department of Animal Science's Poisonous Plants Informational Database.
