Sweet peas: planting, growing, care and use

Description and Botany

The genus Lathyrus, commonly known as “gesse”, includes nearly 150 herbaceous species, relatives of edible peas (Pisum) and vetches (Vicia). Some species of Lathyrus are edible. There are 54 species in Europe and 59 in Turkey! They are common in meadows and fallow land but have much smaller flowers than cultivated forms!

The climbing plant often has winged stems, which helps to differentiate it from vetch, as well as tendrils that allow it to cling to various supports.

The term sweet pea refers to a category of annual cultivars with large flowers that are generally fragrant, derived from Lathyrus odoratus. This annual climber, likely native to Sicily and south-eastern Italy, had, according to the writings of John Ray in his Historia Plantarium (1966), small fragrant flowers that were purple or dull burgundy. However, we will also discuss a few perennial species, Lathyrus vernus and latifolius, which are included in our catalogue.

Sweet peas belong to the family Fabaceae (syn. Leguminosae) and the subfamily Papilionaceae due to the shape of the flowers resembling a cloud of butterflies.

The winged, quadrangular stems, somewhat brittle, bear light green alternate foliage, which is unique as it consists solely of a pair of ovate leaflets measuring 2 to 3 cm long, extended by leaflets transformed into tendrils. A pair of stipules (small leaf-like organs) marks the base of the petiole.

Lathyrus odoratus – botanical illustration

Flowering occurs from June to August but can extend for 5 months. The flowers often measure more than 2 cm and are grouped in axillary clusters, attached to the stems by a long stalk that allows for bouquet making. During the Victorian era, this use was particularly popular, leading to the selection of the Grandiflora group, especially by the British breeder Henri Eckford (1823-1905). The Spencer type was created around 1900, characterised by large flowers with undulating petals that have given rise to many current cultivars. The colours are pastel, tangy, or intense, ranging from white, blue, mauve, purple, pink, and pale yellow, offering a solid, bicolour, flamed, or speckled corolla.

The papilionaceous flowers have 5 free petals, with the uppermost, which is also the largest, taking a banner shape, while the others have a shape intermediate between the lip and the tube. There are 10 stamens. The pistil of Lathyrus is distinguished from that of Vicia by its straight or coiled shape, and the presence of hairs only on the upper face, whereas it is entirely hairy or bearded at the base in vetches.

The flowers of the sweet pea emit a strong and delicate fragrance, which has a sweet floral aroma with soft, honeyed, and musky notes, very feminine. Note that some hybrids are scentless as well as the perennial peas. It is impossible to extract the fragrant essence from the flowers, but perfumers have managed to recreate these scents, such as Givenchy with his fragrance Amarige d’Amour (2003) or Caron with The Sweet Pea from My Home (1927).

The fruit is a flat pod that twists, expelling its seeds at a distance. These seeds are toxic, while the flower of the sweet pea can be consumed in salads (source Interfel).

Sweet peas are easy to grow, very popular in cottage gardens and those of our grandmothers. They can be sown or planted from buckets, in open ground, in deep pots, or hanging baskets to cascade down like garlands. Sweet peas root quite deeply in the soil to draw water and nutrients. Just remember to remove faded flowers to encourage further blooming before the pods form.

There are climbing varieties reaching 1.5 or 2 m, bushy ones at 70 or 80 cm, and dwarf ones at 30 cm.

Several colours of sweet peas: Lathyrus ‘Alan Titchmarsh’, Lathyrus ‘Wiltshire Ripple’, Lathyrus ‘Beaujolais’, Lathyrus ‘Route 66’, Lathyrus ‘Cupani’.

The main species and varieties

The most popular varieties

Our favourite varieties

Bushy and dwarf varieties

Perennial species

Lathyrus odoratus Antique Fantasy mixed - Sweet Pea Seeds

This selection of old varieties of sweet peas ranks among the best in terms of colour and fragrance.

• Flowering time July to September
• Height at maturity 1,80 m

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Lathyrus odoratus Elegant Ladies - Sweet Pea Seeds

This selection brings together old cultivars, some dating back to the 16th century. The annual sweet peas from this mix produce well-scented flowers in elegant and refined pastel shades. Their great vigour allows them to cover large areas.

• Flowering time July to September
• Height at maturity 1,80 m

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Lathyrus odoratus Cupani - Sweet Pea Seeds

The Cupani sweet pea or Lathyrus odoratus grandiflora is a vigorous climbing annual plant with bicoloured flowers: purple and blue, distinguished by its abundant and highly fragrant flowering.

• Flowering time July to October
• Height at maturity 2,50 m

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Lathyrus odoratus Fragrantissima - Sweet Pea Seeds

This mix of varieties with solid or bicoloured flowers features an infinite array of shades: white, pink, red, purple, and blue, with flowers sometimes striped, but always highly fragrant.

• Flowering time July to September
• Height at maturity 2 m

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Lathyrus odoratus Matucana - Sweet Pea Seeds

This adorable sweet pea is a bushy and vigorous plant that produces particularly fragrant flowers throughout the summer, in two shades of purple and violet.

• Flowering time July to September
• Height at maturity 1,80 m

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Lathyrus odoratus King Size Navy Blue - Sweet Pea Seeds

This sweet pea is a vigorous climbing annual plant distinguished by its abundant, undulating, intensely fragrant navy blue flowers. Its flowers, 2 to 4 cm long, appear in clusters of 4 to 5, perfect for creating fragrant bouquets.

• Flowering time July to September
• Height at maturity 2 m

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Lathyrus odoratus Painted Lady - Sweet Pea Seeds

Climbing annual plants with bicoloured flowers (pink and white). Their small flowers emit a fragrance considered one of the best since 1737.

• Flowering time July to October
• Height at maturity 1,80 m

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Lathyrus odoratus Nimbus - Sweet Pea Seeds

A very original climbing annual, it bears white flowers speckled with lavender blue.

• Flowering time July to October
• Height at maturity 1,80 m

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Lathyrus odoratus Blue Velvet - Sweet Pea Seeds

Climbing annual with deep blue-violet flowers that show black reflections under the summer sun. Its abundant and highly fragrant flowering continues throughout the summer.

• Flowering time July to September
• Height at maturity 1,80 m

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Lathyrus odoratus Cupid Pink - Dwarf Sweet Pea Seeds

The fragrant vetch is a dwarf annual plant 20 cm tall, with highly fragrant bicoloured flowers: bright pink and pale pink, voted Best Plant of the Year by our customers. Ideal for flowering pots and window boxes throughout the summer.

• Flowering time July to October
• Height at maturity 20 cm

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Lathyrus odoratus Bijou Mixed - Dwarf Sweet Pea Seeds

This selection of dwarf sweet peas with a well-ramified habit offers a very long fragrant flowering in various shades of cream, pink, or red. Very interesting for borders, rockeries, and hanging baskets.

• Flowering time July to November
• Height at maturity 55 cm

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Lathyrus latifolius Red Pearl - Broadleaf Sweetpea

This perennial pea is a carmine pink version of the broad-leaved vetch. This adorable little herbaceous climber offers bouquets of odourless flowers in a very bright pink, almost red.

• Flowering time July to October
• Height at maturity 1,80 m

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Lathyrus latifolius Pink Pearl - Broadleaf Sweetpea

This perennial climber offers a long flowering of odourless clusters in delicate pale pink. The plant, equipped with tendrils, clings to its support on its own. A greedy but hardy plant, resistant to drought, that enjoys the sun and well-drained soil.

• Flowering time July to October
• Height at maturity 1,80 m

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Lathyrus vernus

Small bush with early flowering and long lifespan, with small blue-violet flowers that become almost greenish as they fade. It spreads quickly from April to June, reaching up to 40 cm tall. It blooms well in both shade and sun, even in poor soils.

• Flowering time May, June
• Height at maturity 40 cm

See the product sheet

Sowing sweet peas

Where and when to sow?

You have the choice between sowing in autumn and that of spring, knowing that the sowing month varies according to the growing conditions:

• In a greenhouse or indoors, in a cool room or on a windowsill, sow in March for a final planting in April-May after the last severe frosts;
• under unheated cover, sow in October-November if the temperature does not drop below 10°C. It is possible to sow in March, but the plants will be less robust and later;
• directly in open ground, sow from March-April depending on the climate. You can also transplant seedlings from spontaneous sowing observed in the garden as early as autumn if the mild climate allows it!
• Perennial sweet peas are preferably sown in autumn to encourage their establishment.

How to sow?

Germination takes 10 to 20 days at a temperature of 15 to 18°C.

1- Direct sowing in place

• Deeply aerate the bed with a fork and then add a spadeful of compost or leaf mould to your garden soil before sowing or planting your young plants.
• Sow in clusters (groups of 2 or 3 seeds) at a depth of 2.5 cm. Leave a minimum distance of 30 cm between two clusters, which is about 4 plants per m².
• Mulch the soil to maintain moisture once the seedlings have emerged.
• Be attentive to snails and slugs that love to devour young plants. Set up traps or spread Ferramol pellets, which are harmless to wildlife.

2- Sowing under cover of annual species

1. Harvest seeds from annual sweet peas contained in dry pods during summer or autumn. Do not wait for the pods to open as they will be immediately expelled.
2. Soak the seeds in water overnight before sowing.
3. Fill 10 cm diameter pots with potting soil.
4. Push 3-4 seeds 2.5 cm deep into each pot and then lightly press down with your finger.
5. Water and place the crop under a cold frame or in a greenhouse depending on the sowing period.
6. Initially cover the pot with glass or transparent film to retain moisture, warmth, and allow light to pass through. Remove the film as soon as the cotyledons emerge.
7. Regularly ventilate the crop under the cold frame during the day to prevent the plants from rotting.
8. Do not let your plants grow in pots for too long as this will affect their establishment. Repot them into deeper pots if you need to wait for the end of frosts.

Discover our tutorial:  How to successfully sow sweet peas?

Planting

Where to plant?

Plan to install your sweet peas at the base of a trellis or sunny fence for abundant flowering, in fertile, deep, and rather cool soil, regardless of pH. Be aware that red or purple colours tend to fade if the sun is too intense. Reserve these colours for partial shade, especially south of the Loire.

When to plant?

Wait until the end of the severe frosts to plant your buckets in the ground, especially if the young plants come from a warm greenhouse.

How to plant?

1. When the seedlings have reached the stage of the second pair of leaves, cut the tip of each stem to encourage branching.
2. Water regularly but without excess to promote the growth of the stems.
3. Apply flowering plant fertiliser and remove faded flowers to encourage abundant flowering from June to August.

Perennial sweet peas require spacing of 60 cm to 1 m along a fence or wall with trellis. Even if the growth is disappointing in the first year, remember that the clump thickens over the years.

For pot cultivation, choose a container that is at least 30 cm deep. Check for drainage holes, place a layer of gravel or clay balls at the bottom, then fill it with a good potting mix. Sow directly or transplant young plants.

Pruning and maintenance

To care for your sweet peas:

• Pinch the stems when they reach 15 to 20 cm high to encourage bushier plants.
• Incorporate manure compost at the beginning of spring for perennial species as well as in the area designated for sowing annual sweet peas.
• Apply liquid fertiliser for flowers every two weeks to potted plants.
• Remove wilted flowers regularly, keeping just a few pods to harvest seeds when they are dry.
• Ensure a cool soil is maintained as even temporary drought halts the production of new buds.

Sweet peas are fairly resistant to diseases but occasional attacks of downy mildew (yellow spots and white fluff on the underside) can occur during cool, damp springs, and powdery mildew (white fluff, slowed growth, and poor flowering) can appear during dry springs (see Q&A). Aphids can sometimes be virulent, located at the tips of the stems. Take the opportunity to pinch the stems or the last leaves and apply black soap or fern manure every 10 days if necessary.

Associations

Sweet peas have a touching and quaint flowering that brings a lot of charm to bouquets, hanging displays, and any support they valiantly colonise in a season. They are just as charming and wandering in summer borders, using neighbouring plants or bushes as support. They are inseparable from cottage gardens, much like peonies, hollyhocks, foxgloves, peach-leaved campanulas, and columbines that they can accompany.

For a natural scene, plant them at the back of a flower meadow or a border of gaura, Lavatera trimestris, coreopsis, and cornflowers… Play with the range of sweet pea tones to create vibrant scenes by combining, for example, the orange of nasturtiums and the purple of Lathyrus ‘Cupani’.

An idea for pairing in a border: Lathyrus ‘Albutt Blue’, Linaria purpurea ‘Canon J. Went’, rose ‘Lavender Dream’, rose ‘Comte de Chambord’, Tradescantia virginiana ‘JC Weguelin’.

They can also create beautiful tapestries or borders, mixing colours like those of sweet pea Bijou. The fertile and watered soil of the vegetable garden is equally suitable for sweet peas that you can train to climb on willow tipis.

⇒ More pairing ideas: Pairing sweet peas