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Plant care

Narrow-leaved Everlasting Pea (Flat Pea) care

Lathyrus sylvestris

Also called Narrow-leaved Everlasting Pea, Flat Pea, Narrow-leaved Vetchling, Wood Pea.

RHS H6USDA 5-9Mildly toxic to petsIndoor 1.5–2 m (5–6.5 ft) tall when supported

Watering rhythm

Bright indirect light (just back from a sunny window)

Low to moderate — water during prolonged drought only once established

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Light

Bright indirect light (just back from a sunny window)

Soil

Well-drained, moderately fertile loam or chalky soil; neutral to alkaline pH

Humidity

Low to moderate ambient (40–65% RH)

Temp

-20°C to 25°C

Pet safety

Mildly toxic to pets

Mature size

1.5–2 m (5–6.5 ft) tall when supported

Care at a glance

Light

Narrow-leaved Everlasting Pea is what florists mean by "bright spot, no direct sun" — close enough to a south or east window to feel the brightness, with a sheer curtain or a few feet of distance keeping the sun off the leaves. Grows best in full sun to light partial shade; flowering is significantly reduced in positions receiving less than four hours of direct sun per day. A phone lux-meter at the leaf surface should read 1,500-3,000 lux at noon.

Watering

Water narrow-leaved everlasting pea low to moderate — water during prolonged drought only once established. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Established plants are reasonably drought-tolerant but will perform best with occasional deep watering during dry summers; overwatering and waterlogged soils cause root rot.

Soil and pot

Narrow-leaved Everlasting Pea grows best in well-drained, moderately fertile loam or chalky soil; neutral to alkaline ph. Tolerates a range of soil types from sandy to clay-loam but demands good drainage; fix nitrogen through root nodules so additional feeding is not required. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Narrow-leaved Everlasting Pea sits happiest at around Low to moderate ambient (40–65% RH) humidity and -20°C to 25°C (-4°F to 77°F). Adapted to open, airy conditions on woodland margins and scrub; good air movement around foliage reduces fungal disease on the large leaflets. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed narrow-leaved everlasting pea sparingly. No regular fertiliser is needed; as a nitrogen-fixer it meets its own needs, and high-nitrogen feeds promote rank foliage and reduce flowering. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on narrow-leaved everlasting pea in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Powdery mildew in late summer — Leaves become covered in white powdery coating from midsummer onward, especially during warm, dry periods; improve air circulation, avoid overhead watering, and remove affected leaves promptly.
  • Spread by rhizome crowding out neighbours — Can become invasive in borders, suppressing smaller plants; divide and restrict the root spread every few years, or grow in a contained planting pocket.

Propagation

Sow fresh seed in autumn or scarified seed in spring into deep pots (taproots form early); established clumps can be divided with care in early spring, though plants resent root disturbance and may sulk for one season after division. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Narrow-leaved Everlasting Pea is mildly toxic to pets. Seeds and foliage contain lathyrogen toxic amino acids, principally beta-aminopropionitrile (BAPN), which interfere with collagen cross-linking and cause lathyrism — neurological and vascular damage with prolonged large-quantity ingestion. ASPCA records primary toxicity to horses; the related Lathyrus latifolius is listed as non-toxic to cats and dogs for typical exposure levels. Prevent pets from eating seeds; classified as mildly-toxic given the shared genus profile. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Narrow-leaved Everlasting Pea care — frequently asked questions

What is the common name for Lathyrus sylvestris?

Lathyrus sylvestris is most commonly called Narrow-leaved Everlasting Pea, but it is also known as Narrow-leaved Everlasting Pea, Flat Pea, Narrow-leaved Vetchling, Wood Pea. The names refer to the same species, so care instructions for Narrow-leaved Everlasting Pea apply identically to anything sold as Flat Pea.

How much light does narrow-leaved everlasting pea need?

Narrow-leaved Everlasting Pea grows best in bright indirect light (just back from a sunny window). Grows best in full sun to light partial shade; flowering is significantly reduced in positions receiving less than four hours of direct sun per day.

How often should I water narrow-leaved everlasting pea?

Water narrow-leaved everlasting pea low to moderate — water during prolonged drought only once established. Established plants are reasonably drought-tolerant but will perform best with occasional deep watering during dry summers; overwatering and waterlogged soils cause root rot. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is narrow-leaved everlasting pea toxic to cats and dogs?

Narrow-leaved Everlasting Pea is mildly toxic to pets. Seeds and foliage contain lathyrogen toxic amino acids, principally beta-aminopropionitrile (BAPN), which interfere with collagen cross-linking and cause lathyrism — neurological and vascular damage with prolonged large-quantity ingestion. ASPCA records primary toxicity to horses; the related Lathyrus latifolius is listed as non-toxic to cats and dogs for typical exposure levels. Prevent pets from eating seeds; classified as mildly-toxic given the shared genus profile.

What USDA hardiness zone does narrow-leaved everlasting pea grow in?

Narrow-leaved Everlasting Pea is rated for USDA zone 5-9 and RHS hardiness H6. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Narrow-leaved Everlasting Pea deep-dive guides

Every aspect of narrow-leaved everlasting pea care, each with its own calibrated guide:

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Narrow-leaved Everlasting Pea qualifies for 5 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Narrow-leaved Everlasting Pea is also known as Narrow-leaved Everlasting Pea, Flat Pea, Narrow-leaved Vetchling, and Wood Pea.