Swainsonpea
Sphaerophysa salsula
Washington State Classification
Class C — Widespread, County-Selected Control
Swainsonpea poses a serious threat to areas where grain is grown.
Quick Reference
Identification
Growth Habit
Swainsonpea is a perennial plant, much branched from the base with a woody taproot and rhizome.
Leaves
Leaves are alternate on the stem and pinnately compound, with each leaf having 9 to 25 leaflets with silvery hairs.
Flowers
Flowers are brick red to purple, pea shaped and occur in 5 to 12 flowered axillary racemes.
Fruit & Seeds
Seed pods (legumes) membranous and inflated 0.6 inches to 1.2 inches long by 0.4 inches to 0.6 inches wide, containing many seeds.
Impact
Swainsonpea poses a serious threat to areas where grain is grown. Since Swainsonpea seeds are the size of alfalfa seeds, it can be a serious contaminant in alfalfa grown for seed. It is known as a troublesome and persistent weed. Swainsonpea was changed from a Class B to a Class C noxious weed in 2013.
Ecology & Spread
Habitat
Swainsonpea is found growing along roadsides, waste areas, fence rows and in cropland. Please click here to see a county level distribution map of Swainsonpea in Washington.
Spread Mechanisms
Reproduction
Swainsonpea reproduces by seeds and rhizomes.
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