Grow fragrant sweet peas

Annual sweet peas (Lathyrus odoratus) are famed for their colourful fragrant pea-like flowers that are perfect for picking.  Fill a small vase with sweet pea stems and they will fill a room with the most beautiful scent.  These delightful climbing plants can be grown in pots or in the ground to provide fabulous displays for the garden and home.   They are often grown for competitions with gardeners seeking the prize for the most perfect blooms. 

Sweet peas are loved by gardeners, being traditionally used in cottage or cutting gardens.  It isn’t necessary to have a large garden though - you can plant up a pot or two of sweet peas for small patios or balconies and enjoy their colourful blooms.  As they start to grow sweet peas will need support such as a frame or obelisk to climb up.

(Lathyrus latifolius is a perennial species of sweet pea that will grow back every year, but most varieties lack fragrance.  In this blog we will be focusing on annual sweet peas.)  

Sweet pea history: 

The story of the sweet pea begins in Sicily where it was first recorded as a wild flower by a Sicilian monk named Franciscus Cupani in 1695.  In 1699 Franciscus was writing a Flora of Sicily and sent seeds of Lathyrus odoratus to various plant collectors and institutions and some came to England.  In the late Victorian era they were cultivated by Henry Eckford and became very popular.  Over the past decades there have been so many sweet pea developments with a huge number of varieties now being available including dwarf varieties for containers.  


Annual sweet peas are easy to grow and are sown undercover in either autumn (October - November) or late January to April and then planted out in April.  Some gardeners like to leave the seeds on damp kitchen paper for 24 hours before sowing to aid germination as sweet peas have a hard seed coat.  

Sweet peas prefer a deep, narrow root run to give them a strong start.  Haxnicks Rootrainers are perfect for sowing sweet peas as they encourage strong, vigorous, straight root formation and avoid pot bound plants.  Rootrainers open like a book to allow you to inspect root progress, moisture levels and easily remove young plants when they need planting out.     

Sow two seeds per pot into a seed compost pushing each seed approximately 1cm below the surface and water them.  Label the pots with the date and sweet pea variety.  Put them somewhere to germinate such as on a windowsill,  in a propagator or greenhouse and do not water until the seedlings appear which usually takes around 10 - 14 days.  When the seedlings are showing keep them cool at around 5°C (40°F).  Plants should be checked regularly and watered lightly if the surface starts to look dry.  

When the plants have formed three to four pairs of leaves pinch out the tips of each one just above a set of leaves.  This will encourage them to produce side shoots which will make them bushier, more robust and the plants will produce more flowers.  

Spring sown sweet peas can be planted out when the risk of frosts have passed.  Autumn sown plants will need potting on into large pots before planting out to avoid getting pot-bound.  

Sweet peas can also be sown directly into the ground in spring when the risk of frost has passed.   

Planting out: 

The soil should ideally be prepared at least four weeks before planting out the sweet peas.  Mix in some organic matter such as garden compost, well-rotted manure or leaf mould.  Sprinkle on some general purpose fertiliser following the recommended dose stated on the pack.  

Before planting the sweet peas out in their final positions it is best to gradually acclimatise them to outdoor temperatures by placing them outdoors for around a week.  You can put them back undercover at night if it is going to be particularly cold.  

Sweet peas need a bright, sunny, well-drained spot in the garden.  Remember to choose somewhere that is easily accessible for regular picking.  Alternatively, they can be planted into large containers for the patio or balconies.  Sweet peas dislike very wet, heavy soil which can cause the plants to rot.  They will not thrive on very dry, poor soil and will not flower well in the shade.   

Place your chosen support frame into position before you begin planting.  Carefully remove the sweet peas from their pots and place two to three seedlings in each hole to give nice full displays.  Each group of seedlings should be planted about 15cm apart.  


Most sweet pea varieties have tendrils that self-cling to their supports, but some will require tying in.  

Keep your sweet pea plants well watered and begin feeding either weekly or fortnightly using a high potash fertiliser such as tomato food when the flower buds start to appear.  

Regular picking will encourage more flowers to form and the flowers will fill your home with beautiful scent.  

Removing the tendrils will ensure that the plants put all their energy into flowering. 

Finally, if you don’t have time or do not wish to grow your own sweet peas from seed, you can buy plants here at Poplar from early spring.