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Broad-leafed and narrow-leafed perennial peavines identification and control
Information about the weeds of concern broad-leaved and narrow-leaved perennial peavines. These introduced peavines are also known by their Latin names, Lathyrus latifolius and Lathyrus sylvestris.
About this weed
Broad-leafed peavine and narrow-leafed perennial peavines are considered weeds of concern in King County, and broad-leaved perennial peavine is on the monitor list of the Washington State Noxious Weed Control Board. This means control is not required, but is recommended, and new plantings are discouraged.
Broad-leaved perennial peavine is known as Lathyrus latifolius and narrow leafed peavine is known as Lathyrus sylvestris. Both are in the pea family. Broad-leaved perennial peavine’s other common names include perennial peavine and everlasting pea. Narrow-leaved perennial peavine is also known as flat pea.
Why it's a problem
Broad-leaved and narrow-leaved perennial peavines have the potential to grow and overtake any frequently disturbed area from riparian (habitat along rivers and streams) corridors to roadsides. They grow vigorously and can climb over other plants, outcompeting them. This can prevent the regeneration of native understory. They are also toxic to humans and livestock if consumed in large enough quantities.
Plant description
Both introduced peavines are originally from parts of Europe. Narrow-leaved perennial peavine is also from parts of Africa and Asia. They are often used as an ornamental plant. They are sometimes sold in “wildflower mixes”.
Growth becomes very dense. It often covers all low-growing vegetation. The flowering plants are most obvious from mid-June until September or October.
Broad-leaved perennial peavine (L. latifolius)
Broad-leaved perennial peavine is a perennial (2+ year life cycle) herbaceous (non-woody) vine. The stems are hairless with broad wings. They can grow 6 to 7 feet long.
The leaves are blue-green with an elongated oval shape and compound. They alternate along the stem with a winged petiole about 2 inches long and leaflets occur in pairs. The leaves are smooth about 3 inches long and 1 inch across. Branched tendrils occur between the leaves.
The pea-like flowers can be white, pink, or red and grow about an inch long. They grow in clusters of 5 to 15. The flowers are unscented.
Brown seeds form in pods resembling edible peas. The seed pods twist and eject upon maturation. They can shoot up to 20 meters away from the plant. It can also reproduce vegetatively from its taproot and rhizomes (roots that spread outwards and can grow new stems).
L. latifolus prefers full sun and loam or clay loam that is moist or partly dry.
Narrow-leaved perennial peavine (L. sylvestris)
Narrow-leaved perennial peavine can grow 5 to 7 feet by climbing with its tendrils. Without support it can reach 30 inches tall.
Leaves are alternate with short, winged stalks. The leaf blades have a single pair of narrow leaflets with tendrils occurring between the leaflets.
Flowerheads have a long stem and 3 to 10 pinkish-red flowers.
Narrow-leaved perennial peavine has smaller flowers but can grow as tall as broad-leaved peavine.
Rhizomes (roots that spread outwards and can grow new stems) are the primary reproductive strategy, but seeds are also used to reproduce. They cannot shoot as far as L. latifolius because of shorter pods and the position of the seeds in those pods. The seed and pod are black or dark gray in maturity.
Both peavines are well adapted to many soil types but L. sylvestris prefers moderately well drained or drier soils. It can also tolerate mild shade.
Be aware of look-alike plants
Key differences between narrow-leaved and broad-leaves peavines are the pod size, leaf size, and flower size. As the name implies, narrow-leaved peavine is the smaller of the two.
The introduced peavines may be confused with these native peavines:
Lathyrus japonicus - Burke Herbarium Image Collection
Lathyrus nevadensis - Burke Herbarium Image Collection
Lathyrus polyphyllus - Burke Herbarium Image Collection
When in doubt, take photos and share them with us or report them on iNaturalist.
What to do if you find it
Because broad-leaved and narrow-leaved perennial peavines are so widespread, property owners in King County are not required to control it. We are not generally tracking infestations. We can provide advice on how to control broad-leaved and narrow-leaved perennial peavines, but there is generally no legal requirement to do so. The King County Noxious Weed Control Board encourages property owners to remove broad-leaved and narrow-leaved perennial peavines where possible, and to avoid introducing it to new landscapes.
Control methods
We recommend using a combination of methods to control weeds. In areas with few weeds, it is important to act quickly before they become harder to control. Make a long-term plan as it often takes several years to get rid of most weeds. Start in the least infested areas first and then move into more heavily infested areas.
Manual control
Small infestations can be hand pulled or dug out. This will be easiest when the ground is moist. Try to remove the entire root for maximum effect.
Pulling or digging will disturb the ground and will likely encourage growth of the seeds already in the soil. Long term monitoring (3 to 5 years) is critical to control an infestation.
Cultural control
After control, planting a ground cover to compete with seedlings may help in the long term.
Mechanical control
Cutting stems to remove above ground growth is only a temporary solution. The roots that remain will resprout. However, this can be useful to reduce biomass. Future work can be reduced by increasing accessibility and preventing seed-set for the upcoming season. Follow up will be required to control these species.
Covering recently cut plants with a heavy-duty fabric or other covering material may also be used. Several visits during the growing season are recommended for best results.
Chemical control
Stay safe when using herbicide:
- Always read the label before use.
- Wear a long-sleeved shirt, long pants, shoes, and eye protection.
- Follow state and local regulations.
Spray herbicide on actively growing plants in warm, dry weather. Several herbicides have been useful in controlling the introduced peavines including glyphosate, imazapyr, and triclopyr. Avoid spraying while flowers are in bloom. It is less effective and can harm pollinators.
Disposal instructions
Bag and dispose of rhizomes and seeds, the rest of the plant may be composted.
Washington State Noxious Weed Control Board pamphlet on noxious weed disposal