The sweet pea (Lathyrus odoratus) is a popular ornamental annual plant admired for its intensely fragrant flowers and vibrant colors. Cultivated for centuries, this climbing vine is a staple in many gardens, adding vertical interest and a lovely scent. The process of growing these beautiful blooms begins with the seed, which contains the genetic information for the plant’s growth. Understanding the characteristics of the seed is the first step toward successful cultivation.
Detailed Physical Characteristics
Sweet pea seeds are generally small, globular, or slightly oval, typically measuring around four millimeters across. Their appearance varies significantly by cultivar, commonly exhibiting shades of brown, tan, gray, or sometimes a speckled or mottled pattern. This color variation is often linked to the eventual flower color; darker seeds may produce blue or purple flowers, while lighter seeds may yield pink or white blossoms.
The most notable physical characteristic is their hard, tough outer coating, which contributes to seed dormancy. This seed coat can feel smooth, rough, or slightly wrinkled and serves as a protective barrier. The seeds develop inside a small, hairy pod (a legume fruit), which ripens from green to brown before splitting open. Each pod generally contains three to six seeds, which are naturally expelled as the pod dries and bursts.
Preparing Seeds for Planting
The hard exterior of the sweet pea seed, while protective, can delay or prevent germination by inhibiting water absorption. Preparing the seeds before planting is necessary to break this physical dormancy and ensure uniform sprouting. This preparation focuses on two primary techniques: scarification and soaking.
Scarification
Scarification involves physically altering the seed coat to allow moisture penetration. This is accomplished by gently nicking the seed with a sharp knife or rubbing it with sandpaper or a file. Perform this action on the side opposite the hilum (the small scar where the seed was attached) to avoid damaging the internal embryo. Creating a tiny opening bypasses the natural delay mechanism of the seed coat.
Soaking
Following scarification, the seeds should be soaked in warm water for 12 to 24 hours. The purpose of soaking is to fully hydrate the seed’s internal tissues, a process accelerated by the break made in the seed coat. Seeds that swell noticeably after soaking are ready for planting, having absorbed the necessary moisture to begin germination. Any seeds remaining small and hard may require a second round of scarification before planting.
Important Safety Information
Sweet pea seeds are not edible and should not be consumed by humans or pets. The seeds of Lathyrus odoratus contain a toxic compound that can be harmful if ingested. This is a significant distinction from the commonly eaten garden pea (Pisum sativum), which is a different species.
The seeds contain a neurotoxin that can cause osteolathyrism, sometimes called odoratism, which affects connective tissues. While small-scale ingestion is unlikely to cause severe poisoning, consuming the seeds over weeks or months can lead to a paralytic syndrome and other serious health issues. Exercise caution and ensure that the seeds are stored securely and kept away from children and foraging animals.