how to plant, grow & care for sweet peas
- Written by:
- Sarah Raven
- Last updated:
complete growing guide
We have teepees and arches covered with sweet peas in flower during June and July – they fill the garden, house and life with scent and colour. They are the stars of our summer season. The range of sweet peas to enjoy is huge, from rich, saturated blues and purples, to pastel shades and luscious bi-colours. There are long-flowering ones with whopper stems, as well as compact ones that are good for pots. They all have fantastic fragrance and can be cut and brought in to fill the house with scent.
- Common name: Sweet Pea
- Latin name: Lathyrus odoratus
- Type: Hardy Annual / Hardy Annual Climber
- Height: Some compact varieties are suitable for pots, however most reach around 1.8m (6ft)
- TLC rating: It can take a little patience and dedication to look after sweet peas – but it is worth it
- Aspect: Full Sun
- Planting position: Borders
- Suitable for pots: Compact forms can be grown in pots but most are better in borders
- Good for pollinators: Yes
- Good for cut flowers: Yes
how to grow sweet peas
where to grow sweet peas
Soil type: A fertile soil which retains moisture but drains well is best for sweet peas.
Aspect & position: Sweet peas love sunshine, so find a position in full-sun.
when to plant sweet peas
Sow sweet pea seeds between October and April. For best results aim for late October/November or late February/March as temperatures and light levels are less than ideal in midwinter. Sweet peas can also be sown direct into the ground in April or May. Plant out your sweet pea seedlings and plants during a mild spell between March and May.
how to plant sweet peas
sowing sweet pea seeds
Sweet peas have a hard seed coat. To aid germination you may find it helpful to leave them on some damp kitchen paper for 24 hours before sowing.
Sow sweet pea seeds undercover between October and April. Rootrainers or loo rolls are ideal as they provide a deep, narrow root run. If you sow into a short, stumpy pot, it doesn’t give the roots as much chance to grow and branch.
To sow the seed, use a peat-free, multi-purpose potting compost and sow two seeds per pot. Dampen the compost, then, with your finger, push each seed in 2-3cm below the surface of the compost. Then label the pot if needed.
If sowing in autumn or spring, sweet peas can be germinated in an unheated greenhouse or cold frame. If sowing in mid-winter, germinate them on a windowsill, heated propagator or very gently heated greenhouse.
Mice love sweet pea seeds and your whole crop may disappear in one go so keep them somewhere mouse-free or try soaking the seeds in liquid seaweed fertiliser before sowing to make them unpalatable.
Check for germination every day and don’t water until you see seedlings start to come through, usually in 10-14 days. Once the seedlings appear, keep them cool at about 5°C (40°F). This promotes root growth, rather than stem growth, which is exactly what you want. An unheated greenhouse or cold frame is usually sufficient.
When there are three or four pairs of leaves, pinch out the leaders – just squeeze off the growing tip between your finger and thumb. This promotes vigorous side shoot formation, with the energy of the plant directed toward growing out, not up.
Check your plants regularly and water them lightly if the surface begins to look dry. About a month from germination, check the bottom of the pot for white roots.
If you sowed your sweet peas in spring, they can be planted directly outdoors during a mild spell in March-May. If you sowed them in autumn or winter, you’ll need to pot the plants up in their pairs. Don’t let them get pot-bound in the rootrainers, they will never be quite the same again. A slim, deep, 1 litre pot is ideal. Use a good compost and water them in. Once the roots have filled that pot, it’s time to plant them outside – do this during a mild spell in March-May.
planting sweet pea seedlings
Once your seedlings are ready to plant out, dig plenty of organic material in the planting position. Farmyard manure is good for sweet peas – it helps retain water on a freely drained soil and gently feeds these hungry plants.
Make sure you plant your sweet peas alongside a vertical support such as a teepee, an arch or a tunnel. Plant 2 plants to each rod of a vertical support. Plant them 15cm (6in) apart.
Surround them with slug prevention. I use at least a 30cm (1ft) wide strip of washed inland sharp sand, 5cm (2in) deep.
As the young sweet pea plants begin to grow, tie them into the frame – don’t leave them to flop around. They’ll grow more quickly and make stronger plants tied in regularly. Do this twice in the first month and then more often when they start to romp away.
Feed your sweet pea plants every couple of weeks after the first month in the ground, especially important if the soil is not very fertile. A tomato feed or comfrey feed is ideal.
Once the flowers emerge, pick, pick, pick and fill up your vases. If you see any seed pods as you’re cutting, snip these off as well. You don’t want your plants forming seed or it will stop the plants producing flowers.
The stems on sweet peas get shorter as the season progresses, this is normal due to the energy used to make the flower. Feed, water and deadhead very regularly to encourage more flowers to appear.
growing sweet peas in a pot
Sweet peas can be grown in deep container pots with a climbing frame. Make sure you choose a compact or dwarf variety.
You can buy a small teepee for a pot, or make one. To make one, push birch or hazel twigs about 120cm (4ft) tall firmly into the compost around the perimeter of the pot – push them about 30cm (1ft) down. Gather the ends and tie them in a bundle at the top using twine or flexi-tie. The sweet peas can then scramble over the twiggy teepee.
how to care for sweet peas
Sweet peas need thorough watering. If you let them dry out, they will get stressed. Water them regularly and every day during a drought.
Feed your sweet pea plants with a general fertiliser every couple of weeks, or sprinkle on comfrey pellets. A potash-rich tomato feed is ideal. If you maintain a good watering and feeding regime, the sweet peas can go on into August.
Sweet pea plants need vertical support and will need a frame to clamber and climb over as they often reach over 1.8m (6ft) tall. A teepee or arch is ideal and you can buy these ready made or make these yourself.
As the young sweet pea plants begin to grow, tie them into the vertical support. It's really important to tie in your sweet peas as they’ll grow more quickly and make stronger plants if they are tied in regularly. Do this twice in the first month and then more often when they start to romp away.
We generally tie in our sweet peas every seven to ten days to ensure they're growing vertically, and sometimes even more depending on the season.
For my guide to tying in sweet peas, take a look at the video below.
It is very important to deadhead your sweet peas. Look out for seed pods developing and snip them off regularly. This prevents the plants forming seed, which would stop the plants producing flowers.
Professional growers who are going to compete in horticultural shows will tell you to pinch out all the curly stems and tendrils. They take energy from the flowers and attach themselves to flower stems and bend them into curves. It’s a lot of work if you are growing a lot of sweet peas. I try to remove any I see while I pick, but I don’t get bogged down.
If you have any seed pods at the end of the season, you can collect the seed and store them in a labelled envelope and allow them to dry for a month or so. Then store in a paper bag in a container in the fridge, ready to plant in winter. The resulting plants may well vary slightly from the parent, especially if you grew a mix of varieties.
- You can plant your young sweet pea plants directly outside from March–May. Sweet pea seeds sown in autumn or winter will need to be potted on into larger pots before planting out. Those sown in spring can be planted out from their rootrainers.
- Pick your sweet peas and arrange them in vases indoors. Continue to deadhead your sweet peas by removing the seed pods. At their peak, you’ll need to pick and deadhead every couple of days.
- Cut down your sweet peas when they finish flowering, but leave the roots in the ground as they have little nodules on them which will add nitrogen to your soil.
- You can start sowing sweet pea seeds as early as mid-October and continue through the winter.
pests, diseases & common issues
Mildew can be a problem for sweet peas, particularly if they are not getting enough water. To help overcome this, water more or try spraying your sweet peas every two weeks with homemade chive tonic. This has a high sulphur content and is a good natural anti-fungicide, which will help slow the spread of mildew. This can be prepared by chopping a large handful of chives into a jug and covering with boiling water. Allow this to steep then strain and use as a spray for your plants.
why are my sweet peas dying?
Sweet peas are thirsty, hungry plants, so make sure you are watering and feeding them regularly. They need plenty of sunlight and will thrive if you continue to tie them in and allow them to grow up a vertical support.
why are my sweet peas not flowering?
Sweet peas need plenty of sunlight to flower prolifically, so make sure they are in full-sun. You also need to deadhead regularly – leaving the seed pods prevents new flowers forming.
why are my sweet peas turning yellow?
Various fungal problems can impact sweet peas and cause leaves to turn yellow. The best way to avoid these is by ensuring your plants are in free-draining soil (that doesn’t get water-logged) and that you mulch around the base.
why are my sweet pea stems so short?
Long stems require the plant’s energy. Tie your sweet peas into their vertical frames so they don’t waste energy holding themselves upright. Water them well so they don’t become stressed in a drought. You can also pinch out all the curly stems and tendrils, allowing the energy to go into growing longer stems and flowers. Towards the end of the growing season the stems tend to become progressively shorter in spite of your best efforts. That said, long stems start with a healthy, happy seedling.
why do sweet peas get mildew?
Dry or stressful conditions can cause powdery mildew in sweet peas. Keep them well-watered on free-draining soil, and mulch around the base of the plant to retain moisture.
why are my sweet pea buds falling off?
Cold nights can cause sweet peas to suffer and buds to fall off. As the weather settles, the problem should pass.
frequently asked questions
are sweet peas edible?
Sweet peas are not edible and can be toxic.
when are sweet peas in season?
The main flowering season for sweet peas is June and July but they can start earlier or go on later, depending on when you sowed and planted them . Keep watering, feeding and deadheading to prolong their season.
how high do sweet peas grow?
Most sweet peas can grow to around 1.8m (6ft). There are more compact varieties available that are suitable for pots and small spaces.
how to germinate sweet pea seeds?
Some people suggest soaking sweet pea seeds to help them germinate - you may find it helpful to leave them on some damp kitchen paper for 24 hours before sowing - however, I have found they germinate within 2 weeks with or without soaking.
are sweet peas poisonous to pets?
Yes, sweet peas are poisonous to pets.
can sweet peas grow in shade?
Sweet peas are sun-loving plants and will thrive in a position that receives plenty of sunshine. They may grow in light or dappled shade, but won’t flower as prolifically.
are sweet peas perennial?
Sweet peas are generally annuals, however Lathyrus latifolius (everlasting pea) is perennial.
what to grow with sweet peas
Sweet peas are best grown on their own on a teepee. They look fantastic as punctuation marks in a vegetable or cutting garden, or to give height and scent to a mixed border. Find out how to create your own sweet pea climbing frames in the article below.
how to cut & arrange sweet peas
The wonderful thing about sweet peas is that the more you pick, the more flowers you get. To ensure they have maximum vase life once inside, I add a drop of sugar syrup into the vase water. To make the sugar syrup, use a ratio of 2 parts sugar to 1 part water and place in a pan over a low heat until the sugar is dissolved.
Get more inspiration for displaying your flowers with our flower arranging videos: