A Comprehensive Guide to Growing Sweet Peas

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.

• 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

• 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 

• 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

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.