Flower:

Clusters of 3 to 10 stalked flowers on stems arising from the leaf axils. Flowers are ½ to about ¾ inch (up to ~18 mm) long, pea-shaped, the upper petal (banner) broad and erect, forming a semi-circle over the smaller lateral petals (wings). Flower color is typically bright pink, but may be white or purplish, and drying blue. The banner and wing petals are often different shades of pink.

The calyx holding the flower is bell-shaped, about ¼ inch long with 5 narrowly triangular teeth, the 2 upper teeth shorter than the 3 lower. The flower stalk is somewhat shorter than the flower and has a thread-like bract at the base. All parts are hairless.

Leaves and stems:

Leaves are compound with a single pair of leaflets at the tip of a winged stalk. Leaflets are 1 to 6 inches long, narrowly lance-elliptic to linear, usually broadest at or below the middle, pointed to blunt at the tip, toothless and hairless. Arising between the leaflets is a long, branched tendril.

At the base of the leaf stalk is a pair of leafy appendages (stipules), up to about 1 inch long with 2 lobes that are narrowly lance-elliptic and pointed at the tip, the larger lobe less than half as wide as the winged stem, usually 1 to 2 mm wide. Stems are branched, broadly winged, hairless, and sprawling or climbing, the tendrils winding around surrounding vegetation for support.

Fruit:

Fruit is a slender pea pod about 2 inches long, initially flat and green, plump and brown at maturity, and containing 5 to 15 seeds.

Notes:

Narrow-leaved Everlasting Pea is not well documented in Minnesota; there are few reports here, though it is more widespread in Wisconsin especially in the northern part of the state. The broad upper petals resemble those of one of the Strophostyles species but the horn-like projections of those species are absent from Everlasting Pea. Besides the flowers, it can be distinguished from other peas by winged stem and leaf stalks, and leaves compound in 2s with a branched tendril between the pair of leaflets. The related Lathyrus tuberosus (Earthnut Pea) also has a single pair of leaflets and similar flowers, but its stems and leaf stalks lack wings.

Distinguishing it from Lathyrus latifolius (Broad-leaved Everlasting Pea) can be more challenging, as it also has winged stems and leaf stalks, a single pair of leaflets with a branched tendril between them, and similar flowers. There is overlap in many characteristics, but in general its flowers tend to be larger, to about 1 inch (to 26 mm) long, the wing petals more often proportionately larger relative to the banner and are of similar color; the calyx teeth more broadly triangular; the leaves shorter, proportionately broader and tending to be broadest near the base; and the larger stipule lobes broader, at least half as wide as the winged stem, though may be less. Again, there is overlap with L. sylvestris on most of these traits so several plants should be examined to get an average for a population.

The population we discovered in Anoka County several years ago was originally assumed to be L. latifolius, since it was unbeknownst to us that L. sylvestris was even present in Minnesota, but a sharp-eyed observer pointed out differences and led us to change our minds (thank you, Chantel).