Perennial pea (Lathyrus latifolius)

Synonyms: Pisum latifolium, Lathyrus sylvestris var. latifolius, Lathyrus sylvestris subsp. latifolius

Common Names: Everlasting pea, everlasting peavine, perennial peavine, perennial sweet pea, wild sweet pea, everlasting vetchling

Description:

Perennial pea (Lathyrus latifolius) is a climbing vine in the pea family, native to south and east-central Europe and northwest Africa [8]. It has been grown in North American gardens since the early 1700s for its showy pink pea flowers, and has escaped to naturalize along roadsides, fencerows, and field edges across much of the United States and Canada [6][7]. MISIN tracks it because it climbs over and smothers other plants, spreads underground by creeping roots that make it hard to remove, and carries seeds that are toxic to people and animals if eaten [3][5].

Habit:

Perennial pea is a long-lived vine that either climbs on whatever it can grab or sprawls into a mound on open ground [1][6]. Where it has support it reaches about 6 to 9 feet; without it, it stays lower, closer to 3 to 6 feet [3][4][6]. The single most useful feature is the stem: it is broadly winged, with two flat, leaf-like flanges running down either side from each leaf joint [1][2]. Run your fingers along it and you will feel the flat edges right away.

The leaves are just as distinctive, because there are so few parts to them. Each leaf carries exactly two leaflets ? oval to oblong, roughly 1 to 4 inches long ? and between them a branched tendril that the plant uses to climb [1][2][3]. Where each leaf meets the stem sit a pair of large, leafy flaps (stipules), up to about 2 inches long ? much broader than in its close relatives, and a good confirming detail [1][9]. The foliage is blue-green [3].

Summer into early fall is the time to look, roughly June through September, when the flowers are open and unmistakable [3][6]. Look for long-stalked clusters of about 4 to 15 pink to rose pea flowers, each up to an inch across, held out well beyond the leaves on a stalk longer than the leaves themselves [1][2][6]. Check roadsides, fencerows, railroad edges, old gardens, and forest clearings [2][6].

At-a-glance cues:

1. Stems broadly winged ? two flat, leaf-like edges running down each side [1][2]
2. Each leaf has only two leaflets, with a branched tendril reaching out between them [1][2][3]
3. Large, leafy flaps (stipules) up to about 2 inches long where the leaf joins the stem [1][9]
4. Long-stalked clusters of 4 to 15 pink pea flowers held above the leaves, summer into fall [1][2][6]

Leaves:

1. Arrangement: alternate along the stem [3]
2. Type: compound, with exactly two leaflets plus a branched tendril at the tip [1][3]
3. Shape: leaflets oblong to elliptical or oval [1][3]
4. Size: leaflets about 1 to 4 inches (30 to 150 mm) long and up to 2 inches (3 to 50 mm) wide [1][2][3]
5. Margin: entire ? smooth and untoothed [1][3]
6. Color: blue-green [3]
7. Stipules: large and leaf-like, about 0.75 to 2.5 inches (20 to 60 mm) long and 3 to 10 mm wide, arrow-shaped to oval, persisting at the leaf base [1][3][9]
8. Leaf stalk: about 1 to 3 inches (25 to 80 mm) long [1]

Stems:

1. Habit: herbaceous perennial vine, climbing where it finds support and mounding or sprawling where it does not [1][2][6]
2. Length: about 2 to 10 feet (60 to 300 cm) [1]
3. Shape: broadly winged ? two flat, leaf-like flanges run down the stem from each leaf joint, giving it a squarish outline [1][2]
4. Surface: smooth to slightly hairy; green [3]
5. Roots: a taproot plus creeping underground stems (rhizomes) that form an extensive network [4][6]

Flowers:

1. Color: pink to rose, sometimes white or purple-tinged [1][2][6]
2. Shape: pea-shaped, with five petals in the irregular arrangement typical of the pea family, and ten stamens [1]
3. Size: about 0.5 to 1 inch (15 to 30 mm) long [1][2]
4. Arrangement: an elongated cluster (raceme) of about 4 to 15 flowers on a long stalk that reaches well beyond the leaves [1][2]
5. Sex: perfect ? each flower has both male and female parts [1]
6. Bloom time: June to September, summer into fall [3][6]

Fruit and seeds:

1. Fruit type: a flattened pea pod about 2 to 4.5 inches (50 to 110 mm) long and 6 to 10 mm wide [1][2]
2. Ripening: pods start green and turn brown as they mature [2]
3. Seeds: about 10 to 15 per pod, with a netted surface pattern [1]
4. Dispersal: ripe pods split open and fling the seeds out, but the seeds are large and heavy and mostly drop near the parent plant rather than traveling far [2][5]
5. Note: the seeds are toxic if eaten in quantity [3][5]

Habitat:

Perennial pea is native to east-central and southern Europe and northwest Africa [8]. It is not native to North America. It has been grown here as a garden ornamental since the early 1700s and has since escaped and naturalized widely across the United States and Canada [6][7].

It is a plant of open, sunny, disturbed ground. Look for it along roadsides, railroad rights-of-way, fencerows, waste areas, open fields, and forest clearings and clearcuts [2][6]. It grows best in full sun and average, well-drained soil, and tolerates some light shade and some drought [6]. In California it is found mostly on roadsides and other disturbed sites rather than in intact natural areas, though it has been recorded producing monocultures ? patches where it is nearly the only plant left ? and invading natural areas [4][5].

Reproduction:

Perennial pea usually arrives in one of two ways: someone plants it, or it creeps in from a patch nearby. It has been a garden favorite for three centuries, and escaped populations trace back to plantings [6].

Underground is where it does its real spreading. The plant grows from a taproot plus an extensive network of creeping underground stems (rhizomes), and this ? not seed ? appears to be its main way of reproducing [4][5][6]. A single plant widens into a patch, and that patch can push in from a neighbor's yard or an old planting along a fence line. It is also why the plant is hard to be rid of once it is established: cutting the top off leaves the network intact, and the roots simply sprout again [2][4].

Seed matters less than you might expect. It does set viable seed, and it blooms and produces seed continuously for more than three months each year, roughly May through September [5]. Ripe pods split and fling seeds out [2]. But the seeds are large and heavy and are mostly moved by gravity, so they drop near the parent rather than blowing to a new site [5]. What that means in practice: the plant creeps rather than leaps, so a new patch far from any other usually means someone moved it or planted it.

For timing your control work, two facts matter. Cut or pull before the pods ripen to stop new seed [2]. And know that digging is likely to stimulate seed germination, so disturbed soil should be watched for a flush of seedlings afterward [2].

Impact and Damage:

The seeds are toxic. They contain a compound that can cause paralysis, tremors, and seizures, and in severe cases can kill; the risk comes from eating them in quantity [3]. Dogs, cats, and horses are all susceptible [3]. Perennial pea is also toxic to livestock, and it is listed in a USDA database as a vertebrate poison for mammals [4][5]. Since the pods look like garden peas, this is worth taking seriously where children, pets, or grazing animals are around.

In the garden and yard, the complaint is that it will not stay put. It spreads by underground stems and self-seeds readily, to the point of becoming weedy, and it climbs structures [3][6]. Its extensive underground network makes it difficult to control once established [4].

For natural area stewards, the concern is smothering. In Oregon the plant is known to overtop and smother native vegetation, and it has been documented forming monocultures and invading natural areas [5]. California's invasive plant council lists it with a "Watch" rating ? its lowest tier ? noting that although it can create monocultures, it is mainly found on roadsides and disturbed ground rather than in intact habitat [4]. A separate risk screening of the same species scored it 16, or "High Potential Risk" [5]. Those two assessments sit in real tension, and both come from the same organization: what it does where it takes hold is serious, but where it takes hold is usually already disturbed. No dollar figure for economic loss from this species was found in the sources reviewed, and no peer-reviewed study quantifying native-plant displacement was located.

Similar species:

Perennial pea belongs to a group of winged-stemmed climbing peas that are easy to mix up. Botanists once treated it as a variety of flat pea, which is a fair measure of how close the two are [8].

Flat pea (Lathyrus sylvestris) is the closest match by far ? another winged-stemmed perennial pea with pinkish flowers, two leaflets per leaf, and climbing tendrils. Check three things. Flat pea's leaflets are distinctly long and narrow, while perennial pea's are broad and oval [1][9]. Flat pea's stipules ? the flaps where the leaf meets the stem ? are narrow, mostly 1 to 2 mm wide, against perennial pea's broad 3 to 10 mm [9]. And flat pea's flowers are smaller, about 13 to 20 mm long, against perennial pea's 18 to 25 mm [9]. MISIN tracks flat pea as its own species.

Sweet pea (Lathyrus odoratus) is the garden annual, and it causes confusion mostly by name ? perennial pea is often sold and labeled as a sweet pea [3][6]. It also has winged stems and similar-sized flowers, so the flowers will not settle it [10]. The life cycle will: sweet pea lives a single year and dies, leaving nothing behind, while perennial pea comes back year after year from creeping underground stems [4][6][10]. A pea in the same spot every spring, spreading outward, is not sweet pea.

Meadow vetchling (Lathyrus pratensis) is a smaller climbing pea of similar habitats. It is told apart by its stems, which lack the conspicuous wings, and by size: its flowers are 10 to 15 mm long against perennial pea's 18 to 25 mm, and its pods are 20 to 50 mm against 40 to 100 mm [1].

Monitoring and rapid response:

Signs to watch for:

1. Vines with broadly winged stems scrambling over fences, shrubs, and roadside banks, or mounding on open disturbed ground [1][2]
2. Long-stalked clusters of pink pea flowers held above the foliage, June through September ? the easiest time to spot it [1][2][6]
3. Patches spreading outward from an old garden planting, fencerow, or roadside [6]
4. Flattened pea pods turning from green to brown in late summer [2]

What you can do:

1. Hand-pull small patches ? this is the method that works at homeowner scale [2].
2. Get the roots out. Cutting the plant off at the soil surface only works temporarily, because the root keeps sprouting [2]. The creeping underground stems are the plant; the vine is just what you can see.
3. Cut or pull before the pods ripen in late summer so no new seed is set, and bag the pods rather than composting them [2].
4. Watch the ground after you dig. Digging is likely to trigger seed germination, so expect a flush of seedlings in the disturbed soil and plan to come back for them [2].
5. Replant the bare spot or cover it after removal ? leaving open ground invites it back [2].
6. Wear gloves, and keep the pods away from children, pets, and livestock ? the seeds are toxic [3][5].
7. Natural area crews: take out small outlying patches first, since the plant creeps rather than jumping long distances and outliers are what start new infestations [5]. Treat a patch as one connected root network rather than counting stems, plan for repeat visits across several seasons, and pay attention to roadsides and clearings, where it establishes [2].

When to call a professional:

1. Large, established patches where digging out the whole underground network by hand is not realistic [4].
2. Sites that keep resprouting after repeated cutting.
3. Roadside or right-of-way situations needing a coordinated, multi-year plan.
4. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Native Plant Trust, Go Botany. Lathyrus latifolius L. (everlasting vetchling). gobotany.nativeplanttrust.org
2. Washington State Noxious Weed Control Board. Perennial Peavine (Lathyrus latifolius). nwcb.wa.gov
3. North Carolina Extension Gardener Plant Toolbox. Lathyrus latifolius (Everlasting Pea, Perennial Pea, Perennial Sweet Pea). plants.ces.ncsu.edu
4. California Invasive Plant Council. Lathyrus latifolius (perennial sweetpea) Plant Profile. cal-ipc.org
5. California Invasive Plant Council. Lathyrus latifolius Plant Risk Assessment (PRE). cal-ipc.org
6. Missouri Botanical Garden Plant Finder. Lathyrus latifolius. missouribotanicalgarden.org
7. Invasive Plant Atlas of the United States. Everlasting peavine: Lathyrus latifolius. invasiveplantatlas.org
8. POWO (2026). Lathyrus latifolius L. Plants of the World Online, Royal Botanic Gardens, Kew. powo.science.kew.org
9. Native Plant Trust, Go Botany. Lathyrus sylvestris L. (flat peavine). gobotany.nativeplanttrust.org
10. Native Plant Trust, Go Botany. Lathyrus odoratus L. (sweet vetchling). gobotany.nativeplanttrust.org

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