Flower profile
Seaside pea
Lathyrus japonicus
Seaside pea (Lathyrus japonicus) is a vine in the Fabaceae family, native in the lower 48 states, blooming mostly May–August across the U.S.
Seaside pea is a wildflower that USDA PLANTS lists as native in the lower 48 states. It's on our flower lists for 4 states, and across the U.S. it's most often seen in bloom in May–August.
*iNaturalist research-grade observations, as of October 17, 2026.
On our lists for: Alaska, Maine, Massachusetts, Rhode Island
Quick look
Lathyrus japonicus, the sea pea, beach pea, circumpolar pea or sea vetchling, is a species of flowering plant in the legume family Fabaceae, native to temperate coastal areas of the Northern Hemisphere.
- It belongs to the Fabaceae family. iNaturalist
- USDA PLANTS describes it as an herb (forb) / a vine with a perennial life cycle. USDA PLANTS
- USDA PLANTS lists it as native in the lower 48 states and records it in 19 states. USDA PLANTS
- NatureServe lists it as native to Massachusetts, Maine, Alaska and Rhode Island. NatureServe
- In Massachusetts, most iNaturalist sightings of it in flower come in May–September. iNaturalist
- In Maine, most iNaturalist sightings of it in flower come in May–July. iNaturalist
- USDA PLANTS lists its flower color as purple. USDA PLANTS
- USDA PLANTS gives its bloom period as early spring. USDA PLANTS
- USDA PLANTS lists a mature height of about 1.5 ft. USDA PLANTS
- iNaturalist has 1,491 research-grade sightings of it in Massachusetts, ranking #102 among the 188 flowers on our Massachusetts list. iNaturalist
- iNaturalist has 1,465 research-grade sightings of it in Maine, ranking #40 among the 160 flowers on our Maine list. iNaturalist
- iNaturalist has 1,140 research-grade sightings of it in Alaska, ranking #39 among the 121 flowers on our Alaska list. iNaturalist
When does it bloom?
Bloom time in the 4 states whose Bloomipedia list includes it
| State | Type | Peak bloom | Sightings* |
|---|---|---|---|
| Massachusetts | Native | May–September | 1,491 |
| Maine | Native | May–July | 1,465 |
| Alaska | Native | June–July | 1,140 |
| Rhode Island | Native | few records (16) | 299 |
Conservation status
- Federal (U.S. ESA)
- Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. USFWS ECOS
- NatureServe global
- G5 Secure worldwide. NatureServe
- Massachusetts
- Not listed Not on Massachusetts Endangered Species Act list (321 CMR 10.90). NatureServe: SNR, not yet ranked in Massachusetts. MESA list
- Maine
- Not listed Not on Maine Rare Plant List (Maine Natural Areas Program, 2021). E and T are Maine's official endangered and threatened plants (12 M.R.S.); SC and PE are tracking categories. NatureServe: SNR, not yet ranked in Maine. Maine rare plant list
- Alaska
- No list Alaska has no state law listing endangered or threatened plants, so we show NatureServe's Alaska ranks instead. NatureServe: SNR, not yet ranked in Alaska.
- Rhode Island
- Not listed Not on Rhode Island Rare Plants 2016 (RI Natural History Survey, from the RI Wildlife Action Plan; informational, Rhode Island has no state plant-protection listing law). NatureServe: SNR, not yet ranked in Rhode Island. RI rare plants 2016
- Rare elsewhere
- Other states where NatureServe ranks it rare or missing: CA (S2), IN (S1), OH (S2), PA (S2), VT (S2). (S1 critically imperiled, S2 imperiled, SH possibly extirpated, SX presumed extirpated.)
Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.
Can you eat it?
None of the sources we checked (NC State Extension (no page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.
It isn't on the ASPCA plant list. For context only: ASPCA lists a related species, Lathyrus latifolius (“Sweet Pea”), as non-toxic to dogs and cats. That doesn't tell us about this species, so keep pets away to be safe. ASPCA
🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.
Where does it grow?
USDA PLANTS records seaside pea in 19 states.
recorded by USDA PLANTS on our state lists not recorded
See the full list of states
Alaska, California, Connecticut, Illinois, Indiana, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Vermont, Washington, Wisconsin.
Massachusetts counties with USDA records: Barnstable, Bristol, Dukes, Essex, Nantucket, Norfolk, Plymouth, Suffolk.
Maine counties with USDA records: Cumberland, Hancock, Knox, Lincoln, Sagadahoc, Waldo, Washington, York.
Alaska counties with USDA records: Aleutians East, Aleutians West, Anchorage, Bethel, Chugach, Copper River, Dillingham, Haines, Juneau, Kenai Peninsula, Ketchikan Gateway, Kodiak Island, Lake and Peninsula, Matanuska-Susitna, Nome, North Slope, Northwest Arctic, Sitka, Yakutat.
Growing conditions
USDA PLANTS gives Seaside pea a medium shade tolerance, medium drought tolerance and medium moisture use. It is rated for soil pH 6.0 to 7.5 and winter lows down to -33 °F.
- Shade tolerance
- Medium
- Drought tolerance
- Medium
- Moisture use
- Medium
- Soil textures it is adapted to
- coarse, medium
- Soil pH range
- 6.0 to 7.5
- Minimum temperature tolerated
- -33 °F
- Frost-free days needed (minimum)
- 190
- Annual precipitation range
- 30 to 60 inches
- Minimum root depth
- 16 inches
- Salinity tolerance
- Medium
- Fertility requirement
- Low
- Growth rate
- Moderate
- Lifespan
- Short
- Active growth period
- Spring and Summer
- Fruit or seed
- Black · Spring to Summer
- Can be propagated by
- seed, sprigs
- Commercial availability
- Contracting Only
From the USDA PLANTS characteristics data for LAJA. USDA ratings are general guidance for the species, not a guarantee for your garden.
Names, range and relatives
Native status by region (USDA PLANTS): Alaska: Native; Canada: Native; Greenland: Native; Lower 48 states: Native; St. Pierre and Miquelon: Native.
County records: USDA PLANTS lists it in 153 counties across 18 states; the most are in Michigan (33), Alaska (19), New York (16).
Other Lathyrus on Bloomipedia (2): Broad-leaved sweet pea, Pacific pea.
More from the Fabaceae family (114 on Bloomipedia; most observed first): Lupines, White clover, Red clover, Eastern redbud, Purple crownvetch, Bird's-foot trefoil, Partridge pea, White sweetclover.
More Massachusetts flowers
Sources
- USDA, NRCS. PLANTS Database, profile LAJA.
- iNaturalist, Lathyrus japonicus: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
- Wikipedia, Lathyrus japonicus (lead quoted under CC BY-SA 4.0).
- Massachusetts: Massachusetts Endangered Species Act list (321 CMR 10.90).
- Massachusetts: Massachusetts Prohibited Plant List (MDAR) (Text from MDAR's 2023 scientific-name PDF (mass.gov blocks automated downloads); 2024-2026 additions listed on the mass.gov page: Alnus glutinosa, Pyrus calleryana, Miscanthus sinensis, Aralia elata, Rhodotypos scandens, Symplocos paniculata.).
- Maine: Maine Rare Plant List (Maine Natural Areas Program, 2021). E and T are Maine's official endangered and threatened plants (12 M.R.S.); SC and PE are tracking categories.
- Maine: Maine Do Not Sell invasive plant list (01-001 C.M.R. ch. 273).
- Alaska: Alaska prohibited and restricted noxious weeds (11 AAC 34.020).
- Rhode Island: Rhode Island Rare Plants 2016 (RI Natural History Survey, from the RI Wildlife Action Plan; informational, Rhode Island has no state plant-protection listing law).
- USFWS, ECOS species database (ESA listing check), October 17, 2026.
- NatureServe Explorer, Lathyrus japonicus (global and state ranks).
- Edibility and toxicity: ASPCA.
- Photo: Michael via iNaturalist · CC BY 4.0 · resized.