Red Sweet Peas in an English Country garden

A Comprehensive Guide to Growing Sweet Peas

Lesley Ann Sandbach
Sweet peas
Sweet Peas growing up a Cotswold Obelisk

We all love sweet peas – long stems of delicately scented flowers in every hue from white through lavender to deep, dark maroon. They can be grown up obelisks , used to cover a fence or combined with other plants They flower from May onwards and will keep flowering if you keep picking them – the perfect addition to any garden!

I hope my tips for planting sweet peas, caring techniques and pest management will give you a long season of these scented climbers.

Planting Sweet Peas

  • The seeds can be planted in either autumn or spring (if you plant the seeds in the autumn, make sure you have room to grow them in a frost-free place, such as a greenhouse, until spring)
  • The seeds germinate readily. I normally soak them for several hours to soften the hard coat but you can help germination by nicking the seed coat with a knife (avoiding the eye of the seed)
  • In spring, begin to harden off the plants by putting them out of doors during the day and bringing them in at night. In order to encourage bushy growth, pinch out the growing centre of the seedlings when they reach about 10cms (4 sets of leaves).
  • Sweet pea plugs and pots of seedlings are also available in garden centres – I find these are useful to add to the number of colours I grow (usually I chose lavenders and pinks with deep purple highlights)
  • Plant seedlings out in late May in rich, moist soil in an area of full sun to partial shade, ensuring that they get at least six hours of sun a day
  • Make a hole slightly larger than the root ball of the seedling, pop it into the hole, firm gently and water in
  • The seeds can also be sown directly into the ground once the soil has warmed up and all threat of frost has passed. Sow the seeds about 6cm deep and 15cm apart in rich, moist soil

Cotswold Obelisks provide the perfect frame to grow stunning Sweet Peas.

Sweet pea seedlings emerge in late May
Sweet pea seedlings emerge in late May
Prick out the tops of seedlings at about 10cm to encourage bushier plants
Prick out the tops of seedlings at about 10cm to encourage bushier plants

Caring for Sweet Peas

  • Whether grown indoors or planted directly into the soil, young sweet pea plants are a magnet for slugs; use beer traps or other environmentally-friendly deterrents to keep the slugs at bay
  • As the plants grow, begin to tie them onto their supports. I grow mine up obelisks near to my runner beans in the hope that each will attract pollinators to the other. I normally plant two seedlings at the base of each leg and tie them in gently with string; many varieties have tendrils that help the plants to climb. Sweet peas are happy to scramble through or over any support and I often combine them with climbing roses in an obelisk – the colours and scents are complementary and the sweet pea plants scramble happily upwards with the support of the frame of rose branches
  • Sweet peas are greedy plants; fertilize them every few weeks with a balanced fertilizer and keep the soil moist (they are prone to drop their flowers if they get too dry)
  • To encourage continuous flowering pick sweet peas daily or remove faded stems; if the plants become leggy a little light pruning to remove leggy or overcrowded growth will do the plants no harm
  • Sweet peas will grow as high as 2m – do provide tall, robust supports for them - an obelisk or a wigwam of sturdy pean poles is ideal 
Sweet peas will climb happily up an obelisk
Sweet peas will climb happily up an obelisk
The plants will grow to 2m in a season
The plants will grow to 2m in a season

Pests and diseases

  • I have found that sweet peas are fairly disease-resistant although common pests like aphids can be treated as they appear
  • The most common ailment is powdery mildew which seems to occur towards the end of the season when the plants have become crowded and air circulation is poor. Avoiding overcrowding is the best way to keep your plants free of fungal disease
Sweet peas grown with runner beans make a colourful display
Sweet peas grown with runner beans make a colourful display

One final thought, we tend to think of sweet peas as being annuals but there are some delightful perennial varieties. ‘Lord Anson’s Sweet Pea’ is my favourite climber - a vigorous violet blue pea that will scramble over fences and through bushes. I also grow Lathyrus vernus, a small clump-forming perennial pea that produces lovely maroon-purple flowers in early April. There’s a sweet pea to suit all gardens.

Lathyrus vernus begins to flower in late March
Lathyrus vernus begins to flower in late March

Obelisks provide the perfect frame to grow your Sweet Peas, check out our range here.


How do I support sweet peas as they grow?

Sweet peas can easily grow 2m in a season so make sure you have a firm support in place for them. I plant mine up obelisks but a strong structure (a row or wigwam) of bean sticks will do as well. Sweet peas will also clamber happily through climbing roses or other climbing perennials

When is the best time to plant sweet peas?

Sweet pea seeds can be planted either in autumn or in spring. If you plant in autumn, keep them in a frost-free, light environment until the danger of frost has passed

What are the ideal growing conditions for sweet peas?

Whether sown directly or planted out as seedlings, sweet peas need rich, moist soil with at least six hours of sun a day

How often should I water my sweet peas?

Although a rich, moist soil will provide all the moisture the plants need, sweet peas will drop their flowers if they get too dry; give them a good soaking if the weather is dry (not little and often but a really good soaking every few days is the answer)

Are sweet peas vulnerable to any common pests and diseases?

Sweet peas are generally easy to grow. Protect them against slugs in the early stages; aphids may attack the plants but soft soap can be used to combat them. The most common problem is powdery mildew which tends to arrive at the end of the season when plants are crowded and air circulation is poor; avoid overcrowding to keep your plants mildew free.

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