Lathyrus (Sweet Pea)

Lathyrus odoratus

A group of annuals (Lathyrus odoratus) and some herbaceous perennials (Lathyrus latifolius) that are mainly climbers. These old-fashioned cottage garden favourites are loved for their brightly coloured and sweetly scented blooms. The climbing forms will easily cling to netting, trellis or cane supports. Low-growing, self-supporting forms are also available. Although a member of the legume family, these plants are toxic and should NOT be eaten.

Family: Papilionaceae (legume, pea, or bean family)
Botanical Name: Lathyrus
Common Name: Sweet pea

Foliage: Deciduous, green, simple pinnate foliage, with tendrils used for climbing.

Flowers: Flamboyant pea-like flowers. Available in a wide range of colours from hues of purple, rose, pink and white. Many species are highly fragrant.

Flowering Period: June to August/september.

Soil: Well-drained, moisture retentive, fertile soil. Best in loam or sandy soil, any pH.

Conditions: Plant in full sun in an east or south facing aspect. Shelter climbers from strong winds.

Habit: Climbing or dwarf bushy.

Type: Annuals, hardy annuals and herbaceous/evergreen perennials.

Toxicity: Seeds and plants are mildly toxic, ingestion can cause lathyrism, which may result in paralysis.

Hardiness: Annuals: Half-hardy. Hardy in coastal and milder areas (down to -5). Annuals usually die after flowering at the end of the season. Perennials: Fully hardy throughout the UK.

Planting and Growing Lathyrus

This old-fashioned cottage garden favourite is easily grown from seed. It needs a humus-rich, fertile, well-drained soil. Soil can be improved before planting by incorporating well-rotted organic mater. Best in full sun but will tolerate some dappled shade.

Provide cane or netting support for climbers. Can be grown through other plants or up fences, walls and other supports.

Suitable for town, city, courtyard, cottage or informal gardens.

Excellent as cut flowers. Stand in water before arranging.

Taking Care of Sweet Peas

Apply a balanced fertilizer once a fortnight during flowering.


Deadhead regularly to prolong flowering. Do not let the plant run to seed (unless collecting seed) as this will stop flowering. Cut back to ground level once flowering has finished. Cut back perennials to ground level in autumn.

Pests and Diseases

Watch for aphids, slugs, snails and thrips. May be affected by mildews and moulds.

Propagating Lathyrus

Propagated easily by seed. Annuals can be sown in a cold frame in early autumn or in early spring or in-situ (where they are to flower) in May. Sow perennials into pots in a cold frame in spring for planting out in autumn. If necessary, soak seed overnight before sowing, to hasten propagation.

Pinch out top shoots when 6in (150mm) high to encourage side shoots.

Popular Varieties of Lathyrus

The annual sweet pea (L. odoratus) is the most widely grown and there are hundreds of garden varieties available. Average height: 18in-8ft (45cm-2.5m), spread 1ft (30cm). Good scented hybrids include:

‘Air Warden’, scarlet flowers.
'Antique Fantasy Mixed', mixed flowers (strongly scented).
'Ballerina', cream with pink edges.
'Charlie's Angel', blue and lavender.
'Cream Southbourne', with frilled petals.
'Charles Unwin ', pink
'The Doctor', mauve.
'Old Times', cream and blue.
'Percy Thrower', lilac.
'Princess Elizabeth', orange-pink flowers or pink on cream.
'Leamington', lavender flowers
'Mrs R. Bolton', pink flowers.
'Red Ensign', red flowers.
'RoyalWedding', white flowers.
'Noel Sutton', blue flowers.
'Winston Churchill', crimson flowers.

Low growing dwarf forms:
‘Bijou’, mix of pastel shades.
‘Knee-Hi’, mixed shades.
'Jet Set', mixed shades.
‘Little Sweetheart’, red, pink, white, rose, purple, lilac, and blue.
'Snoopea', mixed shades.

Perennial Forms (everlasting sweet pea):
L. latifolius, available in white and pink. Height to 6ft (2m). For further details see Climbing Sweet Pea.
L. vernus, non-climbing species. Height 12in (30cm). Ideal for a sunny rockery or container.