Growing fragrant sweet peas for summer bouquets and borders

Sweet peas bring together many things gardeners love: nostalgic scent, romantic colors and a generous display of flowers over many weeks. They can climb fences, frame vegetable beds and fill vases indoors with very little effort once you understand their few key needs.

This guide walks through choosing varieties, sowing, training and caring for sweet peas so you can enjoy armfuls of perfumed blooms from late spring into late summer.

Choosing the right sweet pea varieties

Sweet peas fall broadly into two groups: modern Spencer types and older, often shorter, heirloom types. Spencer varieties usually have large, ruffled flowers on long stems, which are excellent for cutting. Heirloom or “grandiflora” types often have smaller blooms but outstanding fragrance.

If you want flowers mainly for vases, focus on varieties described as long stem or cut flower. For a border or to scramble through shrubs, a mix of vigorous climbers and compact types works well. Many seed packets now label plants by height, scent strength and best use, which makes selection easier.

Understanding their growing conditions

Sweet peas prefer cool roots and mild air temperatures. They grow best in full sun in cooler regions, and in a spot with light afternoon shade in hot climates. Aim for at least six hours of sun each day so plants develop sturdy growth and plenty of buds.

Soil should be fertile, well drained and moisture retentive. Heavy clay benefits from added compost and a little sharp sand, while very light soil needs plenty of organic matter to hold water. A neutral to slightly alkaline soil suits them well, but they are fairly adaptable if drainage is good.

Preparing the soil and supports

Start preparing ground a few weeks before planting. Dig in well rotted compost or garden manure to at least a spade’s depth. This improves structure and moisture balance, which is important because sweet peas dislike drying out around the roots.

Sweet peas are natural climbers, so set up supports before you plant. Traditional options include tall pea sticks (branchy twigs), bamboo wigwams or parallel rows of netting fixed to sturdy posts. Plan for at least 1.8 to 2 metres in height for tall varieties so they have room to climb.

Sowing seeds: indoors or direct in the ground

Gardeners in cooler climates often start sweet peas indoors in late winter. Seeds can be sown in deep pots, cell trays or special root trainers filled with quality seed compost. Plant the seeds about 2 cm deep and keep them just moist in a bright, cool place.

In milder areas, autumn sowing is popular. Young plants are overwintered in a cold greenhouse or frame, then planted out in early spring for very early flowers. Where winters are harsh, spring sowing under cover, followed by planting out after frost danger has passed, is usually more successful.

Helping seeds germinate well

Sweet pea seeds have fairly tough coats. Many gardeners simply sow them as they are and accept slightly staggered germination. If you want more even results, you can soak seeds in room temperature water for several hours before sowing, then drain and plant immediately.

Some people gently nick the seed coat, but this needs a light touch to avoid damage. In general, warmth at the root zone and even moisture matter more than any special treatment. Aim for moderate temperatures and avoid placing pots on very hot radiators, which can dry them out quickly.

Pinching and planting out seedlings

Once seedlings have two or three pairs of true leaves, pinch out the growing tip with your fingers or a clean pair of scissors. This encourages side shoots and results in bushier plants that carry more flower stems later.

Before planting outside, harden off seedlings by gradually exposing them to outdoor conditions over a week or two. Then set them out 20 to 30 cm apart along your supports, planting them slightly deeper than they grew in their pots to help stability.

Watering and feeding through the flowering period

Consistent moisture is essential. Aim to keep soil evenly damp rather than swinging between very wet and very dry. A generous mulch of compost or leaf mold around the plants helps keep roots cool and reduces the need for frequent watering in warm weather.

Sweet peas appreciate regular feeding once they are growing strongly. A balanced liquid fertilizer applied every 10 to 14 days encourages steady growth and plenty of buds. Avoid very high nitrogen feeds, which promote leaf growth at the expense of flowers.

Training vines and keeping them tidy

As vines elongate, gently tie them into their supports every week or so using soft twine or plant clips. This prevents wind damage and keeps stems upright, which improves flower quality and access for picking.

Remove tendrils if you notice them twining tightly around flower stems, as they can distort the blooms. You can also restrict each plant to a few main stems, regularly trimming away weaker shoots to concentrate energy into strong, straight flowering stems.

Cutting flowers to keep them coming

Sweet peas respond to regular picking with more blooms. The more you cut, the more flowers the plant will try to produce. If spent pods are allowed to develop seeds, flowering will slow, so aim to remove faded blooms promptly.

For indoor arrangements, cut stems in the cool of morning or evening when they are well hydrated. Choose stems with several open flowers and some buds. Place them straight into clean lukewarm water, then condition them for a few hours before arranging in vases.

Managing common pests and problems

Aphids often appear on soft new growth. They can usually be controlled by a firm jet of water from a hose, by encouraging beneficial insects or by gently wiping affected shoots. Healthy, well watered plants are better able to tolerate minor infestations.

Powdery mildew may appear late in the flowering period, particularly in dry conditions. Improving air circulation around plants, watering at the base rather than overhead and keeping soil moist but not soggy reduces the risk. Removing the worst affected leaves can help prolong display.

Saving seed for future years

If you grow open pollinated or heirloom sweet peas and are happy with their color and scent, you can save seeds. At the end of the flowering period, allow some pods to mature and dry on the plant until they turn brown and start to rattle.

Pick the pods on a dry day, shell out the seeds and let them dry further indoors. Store them in a cool, dry, clearly labelled container until the next sowing time. Remember that if you grow several varieties close together, cross-pollination can affect the exact traits of saved seed.

With good soil preparation, thoughtful support and regular picking, sweet peas will reward you with weeks of perfume in the garden and indoors. They partner beautifully with vegetable beds and flower borders alike, bringing color and scent to almost any sunny corner.