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Lathyrus japonicus
seaside pea
Lathyrus japonicus
Lathyrus japonicus, commonly known as sea pea or beach pea, is a perennial herbaceous plant in the legume family (Fabaceae) native to coastal regions of the Northern Hemisphere. It features sprawling stems, pinnately compound leaves, and attractive pea-like flowers that are typically purple or pink. It plays a vital role in coastal ecosystems by stabilizing sand dunes and providing habitat and food for wildlife. The seeds have historically been consumed but can be toxic in large quantities.
CategoryDetails
Plant TypePerennial plant
Estimated Plant Lifespan5 years lifespan
Toxic to humansToxic to humans
ToxicityToxic to: Livestock, Pets
Sun Requirements6+ hours direct sunlight (Full Sun)
Pollination

Method: Insect

Notes: Primarily pollinated by bees and other insects. Manual pollination can be performed to increase seed set.

Watering Requirements

Method: Top water

Frequency: Water when the top inch of soil feels dry to the touch.

Notes: Relatively drought-tolerant once established, but benefits from regular watering during dry periods, especially when flowering and setting seed. Avoid overwatering.

Humidity Requirements

Level: Moderate

Care InstructionsDeadhead spent flowers to encourage continued blooming. Prune back excessive growth in late fall or early spring to maintain shape and vigor.
Temperature Range

Min: -15°C

Max: 30°C

Alternative Namesbeach peavine, beach pea, beach vetchling, sea pea, Lathyrus maritimus
Calamagrostis breviligulata
American marram grass
Calamagrostis breviligulata
Both species thrive in sandy coastal environments and help stabilize dunes together. The beachgrass provides shelter, reducing wind exposure for the sea pea.
Solidago sempervirens
northern seaside goldenrod
Solidago sempervirens
Seaside Goldenrod attracts pollinators that can also benefit the Lathyrus japonicus, increasing its seed production. It also provides a visual contrast and creates a diverse habitat.
Cakile edentula
American searocket
Cakile edentula

American Searocket is a fast-growing annual that can quickly colonize disturbed areas and outcompete Lathyrus japonicus for resources, especially in early stages of growth.

Leymus arenarius
lyme grass
Leymus arenarius

Lyme Grass can form dense stands that aggressively spread via rhizomes, potentially overshadowing and outcompeting Lathyrus japonicus for sunlight and nutrients.

Aphids

Aphids are small, sap-sucking insects that can cluster on stems and leaves, causing distorted growth, yellowing, and honeydew production, which can lead to sooty mold.

Spider Mites

Spider mites are tiny pests that suck plant sap, causing stippling or discoloration on leaves. Heavy infestations can lead to leaf drop and webbing on the plant.

Steps:

    • Scarify the seeds by gently rubbing them with sandpaper or soaking them in hot water for 24 hours to break dormancy.
    • Sow seeds in a well-draining seed-starting mix.
    • Keep the soil consistently moist but not waterlogged.
    • Place in a location with bright, indirect light.
    • Transplant seedlings outdoors after the last frost, spacing them appropriately.

Neem Oil

Effective against aphids and spider mites, disrupts their life cycle.

Diatomaceous Earth

Can be used as a soil amendment or pest control; creates a barrier against crawling insects.