Perennial Sweet Pea: How To Grow Lathyrus Latifolius

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Bright pink sweet pea flowers
Image by hongquang09

Quick Perennial Sweet Pea Facts:

  • Botanical name: Lathyrus latifolius
  • Height: 6-10 feet (2-3 m)
  • Spread: 6 feet (2 m)
  • Sun exposure: full sun
  • Soil requirements: Average, well-draining
  • Hardiness zones: 3-8
  • When to plant: Early spring

Many gardeners grow sweet peas – aromatic annual vines with lovely varied colored blooms, but there is also a perennial sweet pea vine. Also referred to as everlasting sweet pea, this perennial pea vine is an old fashioned bloomer that will continue to reward you with color year after year. Interested in growing your own everlasting pea vine? Read on to learn all about a sweet pea vine perennial.

Description of Perennial Sweet Pea

Perennial sweet pea (Lathyrus latifolius) is an herbaceous climbing vine that has been widely cultivated in North America since the early 1700’s. Over time it has become naturalized through most of the United States and Canada and can be found along roads, railroads, fields, fences, and other disturbed areas. It is deer resistant.

The plant has paired leaflets along a vine that either climbs support structures or rambles along the ground. The showy blossoms bloom in the early summer to fall (June through late September) in hues of rose, pinkish-purple or white. Unlike annual sweet peas, the blooms are not fragrant, however they do attract hummingbirds, butterflies and beneficial pollinators. Post bloom, the vine is covered with flat, pea-like seed pods.

Also known as wild sweet pea, this perennial spreads via underground rhizomes or self sows to an extent that it can be termed invasive. The seeds of this species are toxic to some extent.

Perennial Sweet Pea Care

Everlasting sweet pea is an easy to grow vine that has graced home gardens for centuries. Properly cared for, this is a long lasting perennial perfect for covering hillsides, unsightly structures or fencing.

Light

Perennial sweet peas prefer full sun exposure but can be grown in partial sun.

Water

Everlasting sweet peas are somewhat drought tolerant, though they prefer deep watering 2-3 times per week depending upon weather conditions. Use a soaker hose or drip irrigation to prevent fungal disease.

Temperature and Humidity

Perennial sweet peas prefer cool summer climates with temperatures that do not fall below 50 F (10 C) at night. While the plant enjoys consistently moist soil, there is no need for additional humidity. Everlasting sweet peas can be grown in USDA zones 3-8.

Soil

Sweet peas can grow in almost any soil however they thrive in soil that is rich in organic matter. The soil should also be well-draining. This vine is indifferent to pH levels as well as clay, sand, or loam soils.

Fertilizer

Fertilizer is unnecessary, provided the plant was provided soil rich with organic matter at the time of planting. Once the sweet pea plant has established, avoid the use of nitrogen rich fertilizer. Instead, opt for a fertilizer high in potash.

Amend the soil annually as needed with aged manure and compost.

How to Plant Perennial Sweet Peas

Everlasting sweet peas propagate by self-sowing or via rhizomes. Seeds are hard, so they either need to be nicked with a toenail clipper, rubbed with an emery board or soaked in water prior to sowing.

Dig a hole a foot away from whatever support the sweet peas will be using. Sow the seeds when soil temperatures are above 50 F (10 C). Sow seeds a couple of inches (5 cm) apart. Water the seeds well.

Keep the soil moist, but not sodden. Seeds should germinate in 3-4 days. Thin the seeds to about a foot (30 cm) apart.

Pruning Perennial Sweet Pea Plants

Deadhead the sweet pea vine as flowers wane to facilitate additional blooms. Also snip seed pods at this time to encourage blooming over seed production.

Pruning is used to prevent sweet peas from getting out of control and to encourage bushy growth and additional blooms.

In the fall or early spring, cut the plant back to ground level and remove any dead or cut vine from the trellis or support.

Problems, Pests & Diseases

Generally perennial sweet peas are a low maintenance plant with few problems. If it is too crowded or overwatered, it is prone to fungal diseases and pests such as snails and slugs.

Fungal issues related to sweet peas include black root rot, gray mold, leaf spot, mildew, and rust.

Note: Perennial sweet peas are toxic.

Is Perennial Sweet Pea Invasive?

Yes, perennial sweet peas have the potential to be invasive. They readily self-sow and are spread through underground rhizomes.

Perennial Sweet Pea Varieties

Cultivars to look for include Albus, Blushing Bride, Pink Beauty, Pink Pearl, Snow Queen and Splendens.

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