Everlasting Pea is an introduced perennial trailing or climbing vine, growing up to 6 feet in length on green stems that have broad wings and tendrils that arise between the leaflets.
The leaves are compound, but just two leaflets, oval to lance shaped, on winged stalks, with the short branched tendril rising between the leaflets. Margins are entire, surfaces are smooth, each leaflet up to 3 inches long, 3x as long as wide. The leaflets spread out in a 'V' shape. There are leaf like bracts (stipules) at the base of the leaf.
The inflorescence is a long stalked cluster of 4 to 10 individually stalked flowers (a raceme).
The flowers are 5-part like others in the pea family with a larger upright standard (banner) petal which is notched at the top, two much smaller lateral petals that project forward, and a lower keel that is enclosed by two lateral petals, and sort of protected by the two laterals. The corolla is white to purplish red, usually more to the pink-purplish end of the spectrum fading to a dull purple. The banner petal is the brightest, the laterals are usually darker in color and the keel petals lighter in color, if not actually white. The green calyx has 5 unequal lobes ending in 5 pointed teeth. The lowest lobe is longest. Stamens number 10 and there is a single style connecting to the ovary. The reproductive parts are enclosed by the keel petals. There is no fragrance.
Seed: Mature flowers form a pod like a garden pea, but more flattened and without hair, containing up to 15 dark seeds that are flung out when the dry pod splits open. Peas are attached in alternate fashion to the left and right side of the pod.
Invasive and toxic - see notes below.
Habitat: Everlasting Pea grows in waste places - roadsides, railroads, abandoned fields. It grows from a rhizomatous root system, preferring well drained soils and full sun. It tolerates some shade and some drought, but like most pea plants, it is a cool season plant and does best in cooler temperatures.
Names: The genus Lathyrus, is from the Greek word lathyros, which referred to a pea plant of olden times. The species latifolius is from the Latin root lati, meaning 'broad', and used here to represent wide to broad leaves. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: There are two other peas with leaves of two leaflets - Sweet Pea, L. odoratus, where the flowers are fragrant and the inflorescence has only 1 to 3 flowers and the Caley Pea, L. hirsutus, where the pods are very hairy and the inflorescence has only 1 to 3 flowers.
Above: 1st photo - The upright banner of the Everlasting Pea flower is where most of the color is. The lower 2 petals forming the keel are partially enclosed by two small, much darker, lateral petals. 2nd photo - The green calyx has 5 unequal lobes ending in 5 pointed teeth.
Below: 1st photo - Fertile flowers form a pod like a garden pea, but flattened and without hair, containing up to 15 dark seeds that are flung out when the dry pod splits open. 2nd photo - A pod with peas nearing maturity. Note how peas alternate in attachment to the right and left side of the pod. 3rd photo - The dry pod: It splits into two sections and twists into a spiral, which flings out some of the dry peas.
Below: 1st photo - The flower raceme has 4 to 10 individually stalked flowers. 2nd photo - The compound leaf has two oval to lance shaped leaflets. Note the wing on the leaf stalk and the main stem. 3rd photo - A branched tendril rises from the junction of the leaflets. Note the small bract at base of the winged leaf stalk.
Below: A group of plants showing the sprawling ability to climb onto other vegetation.
Notes: Everlasting Pea has been in North America since the early 1700s. It is native to the Mediterranean and was brought in for Garden use as the flowers are quite showy. However, it escapes cultivation easily and is now found in almost all states of the U.S. and several Canadian Provinces. It is present in Minnesota but there is little location information published. As the plants spreads by both rhizomes and seeds, it can become invasive in uncultivated land, but is useful for erosion control . Seeds have a long vitality in the soil.
There are six species of Lathyrus found in Minnesota: L. maritimus, Beach Pea; L. ochroleucus, Cream Pea or Pale Vetchling; L. palustris, Marsh Vetchling; and L. venosus, Veiny Pea are all considered native. Two others are introduced: L. latifolius, Everlasting Pea; and L. tuberosus, Tuberous Vetchling. Only L. venosus and L. ochroleucus are found in the Garden.
Toxicity: Everlasting Pea pods and seeds contain an alkaloid which causes a neurotoxic disease called Lathyrism, which affects the nervous and muscle systems and can result in paralysis. Animals and humans eating uncooked seeds or pods can succumb to this. This is one of the oldest diseases known. Other species of Lathyrus are more potent than latifolius, L. sativus being considered the most potent.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"