How to grow sweet peas
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Choose your seeds
If you are thinking about having a go at growing other varieties for the Show as well as the named variety, you should choose Spencer varieties – this information is always included in the description in catalogues and on the packet. This is because Spencer varieties have large, frilly flowers, long stems and consistently have 4 flowers on each stem. They are the best varieties for showing, but they also have great impact as a cut flower, and of course they are usually highly scented. The best selection will be online from specialist seed growers. The GPHS chooses the variety for our Show following consultation with Somerset Sweet Peas (www.somersetsweetpeas.com), and other varieties they recommend as particularly reliable and suitable for novices are:
Charlie’s Angel
Gwendoline
Jilly
Just Julia
Pink Panther
Sir Jimmy Shand
White Supreme
Sow your seed
For best results, and especially if you want to show your sweet peas, sow seeds in October-November. Later sowings, January to March, are possible if you just want plants for the garden.
• Seeds should be sown and covered with 1 cm of any good multi-purpose compost. See below for options for sowing. There is no need for seed compost.
• You don’t need to soak seeds in water before sowing or nick the seed first, as these practices cause damage and may inhibit germination.
• Mice love sweet pea seeds, so make sure they can’t get at your seeds and seedlings.
• Gently water in your seeds after sowing, but it is best to avoid further watering until germination can be seen, to reduce the risk of disease and rotting off.
• Germination is best at about 15C to 18C and can take place in 7 to 14 days.
• Label them if you have more than one variety.
You have 3 options, but whichever you choose, make sure the containers for overwintering are 12.5cm deep as sweet peas like to send their roots straight down and have a long root run. Using Rootrainers is the recommended option, either for sowing (option 1) or overwintering after transplanting (option 3).
- Put one seed per cell in deep Rootrainers, which have 8×4 cells. These are 12.5cm deep and the plants are left in them until planting time. Rootrainers have the advantage that the each root ball develops separately and they don’t get tangled up together.
- Put 8 seeds in a pot 12.5 cm deep, reducing to the best 6 following germination. Leave them in the pot until planting time the following spring.
- Put your seeds in a standard seed tray. Once the seedlings are about 2.5cm high, they will need to be transplanted into one of the above containers for growing on.
Early growth and overwintering
• Autumn sown seedlings should be placed in a cold frame with plenty of light or a cold greenhouse to over-winter as soon as the seeds have germinated. Do not leave them in a heated greenhouse or indoors. This is because a heated atmosphere will make the shoots grow too quickly and get “leggy”, and the aim is to promote sturdy plants with good root growth. Sweet peas are hardy annuals and will stand moderate frost down to -5C.
• If you don’t have a cold frame or greenhouse, you could put them in a sheltered, sunny spot on a patio, using bricks or other screening to provide a bit more protection. They should not be covered up completely; they prefer fresh air and light.
• Wherever you overwinter your plants, protect them against slugs and check occasionally, renewing slug protection as necessary.
• Finally, pinch out the growing tip as soon as your seedlings have 2 pairs of true leaves. This will encourage side shoots, and the side shoots produce much better flowers than the main shoot.
If in a cold frame, or a sheltered spot outdoors, cover the seedlings just for the first day or two, then lift the cover a couple of centimetres for a few days and then remove the covering completely. Only cover at night if heavy frost or snow is forecast. Check the trays occasionally and tip out excess water, especially after heavy rain.
If they are in a cold greenhouse they must be kept cool on sunny winter days by letting in plenty of cold fresh air. Water them as necessary.
Your sweet pea seedling can be left to overwinter until March when it is time to plant them out.