How to grow sweet peas from seed

Posted in All Gardening Advice, Annuals, March, on

This guide to growing sweet peas from seed will show you how to create fantastic summer sweet pea displays in your garden. If you've purchased ready-to-go sweet pea seedlings from us, read on to the Planting out Sweet Peas section ...
 

How to sow sweet peas

Sow your sweet peas seeds anytime from October until March, two seeds to a pot. You can sow your sweet pea seeds in March but growing sweet peas over winter will produce stronger, more robust plants.

I usually use root trainers – long, thin pots or cardboard loo rolls – to sow my sweet peas into. All legumes, these included, like growing with a long root run, so deep pots like these are ideal. Push seeds in to about an inch below the surface of the multi-purpose compost – dampen the surface and then push each seed in with your finger.

Cover the pots with newspaper or a polystyrene tile to keep moisture and warmth in and light out. Some heat will speed up germination, but is not essential.

It’s very important to set a mousetrap near your sweet peas. Mice love the seed and your whole crop may disappear in one go. You could soak the seeds in liquid paraffin overnight to make them unpalatable and put your mice population off.

Check for germination every day. Once the seedlings appear, keep them cool at about 5 degrees centigrade. This promotes root and not stem growth. A cold greenhouse or cold frame is ideal, but your plants will be fine in a light potting shed.

Pinch out the leader – the growing tip – when there are three or four pairs already grown. Just squeeze it off between your finger and thumb, reducing the plant to one to two inches in height. This promotes vigorous side shoot formation – the energy of the plant going into growing out, not up.
 

Planting out sweet peas

When the roots have filled the Rootrainer, plant them out.

Dig in a barrow load of organic material around the base of a teepee or frame. Farmyard manure is good for sweet peas – it helps retain water on a freely drained soil and gently feeds these hungry plants. On very freely-drained soil tear newspapers into strips and put these in the trench too. They’ll help hold onto water.

Place each pot holding two sweet pea plants 5-7cm away from the support (a teepee, an arch, or a tunnel), so you’re planting two plants 8-10 inches apart at the base of every upright. Surround them with slug prevention. I use at least a foot-wide strip of washed inland sharp sand, two inches deep, all round mine. It acts as a path for picking later on and should keep the slugs at bay.

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, once a fortnight for the first month and then more often when they start to romp away. I use Flexi-ties to do this.

If you garden on poor soil, feed your sweet pea plants with a general fertilizer every couple of weeks, or sprinkle on comfrey pellets. A potash-rich tomato feed is ideal. I don’t feed mine, gardening on a rich, heavy, clay soil.

Professional and serious amateur growers who are going to compete in horticultural shows will tell you to pinch out all the curly stems. They take energy from the flowers, and attach themselves to flower stems and bend them into curves. It’s a lot of work on the scale of a tunnel. I try to remove any I see while I pick, but I don’t get bogged down.

Then just let them get on with it and pick, pick, pick. 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 plants mature, this is normal due to the energy used to make the flower. Simply feed, water and deadhead to encourage more flowers to appear.

Read how to cordon train your sweet peas for magnificent flowers ...

Browse our range of sweet pea seeds or, if you'd rather plant out straight away, our sweet pea seedlings – ready to plant straight out into your garden, for gorgeous scent throughout the summer.