Lathyrus japonicus (Beach Pea)
|Also known as:|
|Habitat:||part shade, sun; sandy soil, mostly lake shores|
|Bloom season:||June - August|
|Plant height:||1 to 2 feet|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Tight cluster of 6 to 10 pea-shaped flowers at the end of long smooth stem arising from the upper leaf axils, the flower stem shorter than the stem of the attending compound leaf. Flowers are ½ to ¾ inch long, about 3/8 inch across, the upper petal (standard) flaring out on the sides, rich purple with darker veination. The pale violet to white lateral wings below it enclose a small light lavender keel underneath. The calyx holding the flower is attached to a short stalk, both are smooth.
Leaves and stem:
Leaves are compound with 3 to 6 leaflet pairs and a branched tendril at the tip, the compound leaves alternately attached along the stem and the leaf stalks distinctly arching. Leaflets are 1 to 2 inches long and about half as wide, oval to elliptic, narrowed at both ends. A pair of leafy appendages (stipules) nearly as large as the leaflets attend the leaves at the base of the leaf stalk; they resemble a pair of stalkless, opposite arrowhead-shaped leaves. Stems are angled and unbranched, with multiple stems arising from rhizomatous root system, forming dense clumps.
Beach Pea is a circumboreal species and can be found along the Pacific coast of North America and throughout parts of Asia and Europe. In Minnesota it is mostly restricted to Superior's north shore with a few inland locations. Its low growth, arching branches and deep pinkish purple flowers are easily recognizable; the only pea type flower it can be mistaken for is the widely distributed Veiny Pea, Lathyrus venosus, whose flowers are nearly identical, but Veiny Pea is a much larger plant, typically to 3 feet tall with more than 10 flowers in a cluster and much smaller stipules with acutely angled tips. Veiny Pea can be found in a variety of habits throughout much of the state. Beach Pea would be an interesting species to try in a sandier garden site though probably would not perform well in hot locations. There are at least two subspecies (or varieties, depending on the reference) of Lathyrus japonicus but they are poorly documented. The species in Minnesota is subsp. maritimus, formerly known as Lathyrus maritimus var. glaber.
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Photos by K. Chayka taken at Flood Bay, Lake County. Photos by Peter M. Dziuk taken along Highway 53 north of Duluth, and in Cook and Lake counties.
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