How to grow & keep your sweet peas flowering all summer long

A guide to growing and retaining your sweet pea flowers all summer long.

If you are new to the world of flowers and experimenting with pollinator plants for your vegetable patch – there is nothing easier or more prolific to grow than sweet peas (Lathyrus odoratus). 

As a beginner vegetable gardener, I was inspired by potager gardens with towers of rambling sweet peas trained up teepees, adding vertical height and interest into otherwise boring garden beds. Sweet peas were somewhat of a ‘gateway’ plant for me – after the first season I was hooked on these beautiful flowers and never looked back. 

While sweet peas seem simple to grow, there are some additional measures to make your season even sweeter and for the best results – keeping these fragrant flowers sparkling throughout the summer. 

Early flowering Sweet Pea 'Spring Sunshine Blush'

Planting time 

Sweet peas are an annual flower, meaning they only live for one growing season. They are hardy, fragrant and can tolerate cooler temperatures and light frosts. 

Whether you are starting from sweet pea seeds or sweet pea seedlings from garden centres, it is a good idea to prepare the garden beds correctly to give them a good jump start. 

Sweet peas are heavy feeders throughout the season, so it’s recommended to amend the soil prior to planting. 

Dig in plenty of organic matter that will keep the soil moist. But sweet peas do not like wet feet, so well-drained soil is important. Think compost, humates, well-rotted manure, sheep pellets, worm castings or blood and bone.  

Succession Planting 

The key to longevity with sweet peas is to master the art of succession sowing. To increase your season, plant a crop of early flowering sweet peas in autumn to late winter. A secondary crop of late flowering sweet peas can be planted in the spring to early summer.  

Early flowering sweet peas are bred to flower with as little as 11 hours of daylight, meaning you will receive flowers earlier. Look for the ‘Spring Sunshine’ series. As the season progresses, you can switch to a late flowering sweet pea which needs at least 12 hours of daylight to flower. 

There are many good varieties of summer flowering sweet peas available. Some favourites include ‘Unwins Royal Wedding’ or any of the Keith Hammet cultivars such as ‘Signpost’ and ‘High Scent’. 

Mulch & Pests 

Once planted, mulch well and keep that mulch topped up throughout the growing season. They cannot be allowed to dry out or they will wither quickly – keep an eye whether your sweet peas have enough moisture in hot weather and the summer heat. 

Any mulch will do – lawn clippings, wood chips, leaf litter or pea straw. Just watch for slugs and snails now, as tender young shoots are irresistible to pests and can quickly be devoured, particularly if the weather is wet. Every night, check out the seedlings and pick off any critters hanging about. Beer traps, crushed eggshells or wool mats can be used to prevent attacks.

Fertilising 

Sweet peas are hungry plants. As the sweet peas grow you will want to apply a nitrogen-based fertiliser like seaweed or fish emulsion – organic is always best. For the first couple of months, apply fortnightly to build up strong root systems and a strong leafy structure. After this you can switch to a fertiliser which contains phosphorus and potassium which will encourage more blooms. A homemade comfrey fertiliser is a good option. 
are suitable for pots, and it’s important to consider the shape and size before planting. But a container display is a chance to be a little creative and have some fun!

Sweet Pea 'Unwins Wedding Royal Wedding'
Sweet Pea ‘Unwins Wedding Royal Wedding’
Keith Hammet 'Signpost' Sweet Pea growing in garden
Keith Hammet ‘Signpost’ Sweet Pea growing in garden
Fence covered in Sweet Peas in the evening light
Fence covered in sweet peas in the evening light

Support, support, support 

As the sweet peas grow, they should be trained up a climbing frame, trellis or structure. This will help keep them tidy but also create flower stems that are long and good for cut flowers. 

Teepees can be fashioned using bamboo canes, at least 2m tall as the sweet peas are rampant growers.

Or grow a wall of sweet peas. My preferred DIY option is to attach pieces of garden wire to a fence using a staple gun and leave the vines to trail up. Sweet peas have tendrils that can twist around twine or wire, but they will need a helping hand. Once a week I will take the time to tie up any loose ends that have fallen from the pack.  

 

Sweet Pea teepees in Vegetable garden
Sweet pea teepees in vegetable garden
Sweet Peas climbing up arch
Sweet Peas climbing up arch
Sweet Peas climbing up wall in vegetable garden
Sweet peas climbing up wall in vegetable garden
Sweet Peas trained up trellis along fence
Sweet peas trained up trellis along fence

Harvesting 

As the sweet peas begin to flower, they will need regular pruning and deadheading to keep the show going. If you can, every single flower should be picked from the vines daily and bundled inside to enjoy their delicious scent. My favourite way to enjoy their fragrance is on a bedside table or bathroom.

Sweet peas do not have the longest vase life however, they are prolific flower producers. Every morning you will step outside and notice the plants are once again smothered in new blooms for cutting. It is exactly this generosity that makes sweet peas so delectable.

Pruning 

It is important not to let the sweet peas run to seed – this is a signal to the plant to stop producing flowers. Instead, keep cutting off the flowers and seedpods if any have developed and watch more flowers come each day.

As the season progresses, the stems on the flowers will grow shorter and shorter. This is normal as the plant uses its energy to create more flowers. To combat the stumpy stems, you can cut the vines along with the flowers for a whimsical display in the vase. This method also helps to keep the unruly plants in check.

Once the vines reach the top of their structure, you can chop the tops off the plants. This forces the sweet peas to grow laterals (side shoots) which will make them have good bushy growth (even more flowers!).

Combatting disease

Powdery Mildew is a common fungal disease that produces a white, powdery film on the leaves, stems and flowers of plants. Spores of the fungus are dispersed through wind, during times of dry warmth and high humidity. Just like your legumes in the vegetable garden, sweet peas are known to succumb to powdery mildew, particularly in the summer. 

Good air circulation is the best measure to combat this issue, therefore do not overcrowd your seedlings at planting time (space 20cm apart) and prune heavily throughout the growing season by removing spindly and weak vines. 

When the inevitable powdery mildew creeps in, treat with a milk solution of 1 part milk, 10 parts water and dowse the foliage once a week. 

However, keeping your plants and rich soil healthy with organic ingredients like seaweed, fish emulsions and worm tea will also help to boost immunity and fight off the fungi spores.

Harvesting seed 

In the autumn time, your sweet peas will begin to tire and fizzle. Use this as an indication to save seed, to sow seeds the following season.

Stop cutting the flowers and allow seed pods to form. Wait for the pod to grow brown and crispy before cutting, which ensures the seed has matured. The sweet pea vines will also start to look untidy in the garden. Transfer the plants to the compost pile – but remember to cut at the base of the plant, leaving the roots intact as  they contain nitrogen nodules that are beneficial for the soil. 



Sweet peas have a way of making even the simplest garden feel abundant. Their allure exists in both their prolific blooms and their whimsical nature. They teach us patience and reward us with handfuls of nostalgia-laden flowers, spilling over vases with their sweet scent. As the season winds down and the plants begin to fade, the cycle of growth reminds us to collect what is left—whether it is a jar of seeds or memories of mornings spent harvesting blooms. 

For the new gardener, sweet peas are more than just flowers. They are an invitation to fall in love with the art of growing. And once you do, there is no looking back. 

Saving sweet pea seeds
Saving sweet pea seeds
Sweet Peas can be cut on the vine for longer stems
Sweet peas can be cut on the vine for longer stems
sweet peas require deadheading everyday to produce more flowers
Sweet peas require deadheading everyday to produce more flowers
Sweet Peas in summer garden
Sweet peas in a summer garden.