Introduction

Sweet peas were first introduced into Britain in the late 1600s and have been giving gardeners great pleasure ever since. Sweet peas are wonderfully versatile and give colour and fragrance wherever they are planted. They make ideal cut flowers and low growing varieties have been carefully developed that require little or no staking making them suitable for bed, borders and edging. The most commonly grown types of sweet peas are the Spencer and Grandiflora cultivars. Both forms climb using twisting leaf tendrils around supports (man-made or other plants and shrubs). The Spencer types have large flowers and may grow as large as 2 - 3m (6 - 10ft) tall. The Grandiflora forms have smaller flowers but are generally more highly scented. Dwarf sweet peas grow to about 90cm (3ft) and make superb tub, hanging basket or Flower Pouch subjects. Some varieties have also been developed with no tendrils and this encourages more flowers.

How to Sow for Best Results

The seed colour varies from a pale cream through to black. Some authorities have said that the darker seeds may need a little more help to germinate than the pale ones. If you have had problems with germination try giving them a helping hand. This is often called scarifying, soaking or chipping. The surface of the seed has a hard coating that stops moisture being absorbed and this can stop or reduce the germination of the seed. All that is needed to help this is for the outer surface to be scratched, rubbed or chipped away to allow the water to pass through. Use a small piece of emery paper to rub over the seed coat; or very carefully, using a sharp knife, chip away a small piece of the seed coat at the opposite or furthest end of the seed to the "eye". Soak the sweet pea seeds in a bowl of hand hot water for 2 hours and then sow immediately.

Direct Sowing

Sweet peas can be sown in mid-autumn in pots (September/October) or early spring in pots or most commonly directly into the soil where they will flower (January to April). Plant during March and April into drills about 2.5cm (1in) deep and about 7.5cm (3in) apart. Mark the row swell and watch out for mice and birds which may damage the seedlings or eat the seed before it has germinated.

Sowing in Pots

Sow two or three seeds 1cm (½in) deep in 7.5cm (3in) pots (deep ones are the best), or root trainers (the smaller seedlings should be removed when potting on). Some companies offer special sweet pea tubes which are about 5cm (2in) in diameter and about 15cm (6in) deep. The compost should be moist, but definitely not wet. Wet compost (which can even be the case straight from the bag) will be cold and reduces the oxygen that the seeds need to germinate. It may even stop the seeds germinating at all! If the compost is too dry this will also cause problems. If this is the case, sprinkle a small amount of warm, clean tap water over the compost and leave it to soak in thoroughly. When the compost has absorbed the water, take a small handful and squeeze it in your fist: if water drips out it is too wet, so leave it for a short while in a well ventilated spot to dry off. If it holds together when you open your hand, it's just about right. You can now fill your pot with the moist compost and you don't have to water it again before you sow the seed.

Cover the pots or tubes with a sheet of glass or place in an unheated propagator and keep the mat about 13-19C (55-65F) until the seeds germinate. As soon as the seedlings start to appear (approximately 10 - 20 days) move them to a well ventilated cold frame. When the first or second pair of leaves has opened, pinch out the growing tip to encourage stronger new growth to develop. Pot the young plants on when they are about 5cm (2in) tall into individual pots or plant outside when the soil starts to warm up in the spring. Remove any small or weak seedlings.

If you are over-wintering seed sown in the autumn, try to keep the frame as open as possible, to harden them off. If the weather is very poor and frosts of below -2C (28F) are expected close the frame and cover with matting, straw or old newspapers to insulate it. Prop the frame lights open in heavy rain for ventilation.

Check the compost for dryness regularly. If this is the case, add a little clean water from below, being careful not to over water. Too much water can kill seedlings, as it can spread "damping off fungi", and encourage other moulds and diseases.

Plant the young sweet peas in a sunny, open, well-drained but humus rich soil. Transplant spring-sown seedlings in late spring and autumn-sown seedlings in mid-spring. For the best results, dig in lots of well-rotted manure in the autumn, then, three or four weeks before you wish to plant, carefully rake into the soil a well balanced, slow release granular fertiliser. Plant about 20cm (8in) apart and a few cms (½in) away from their support, the bottom shoot should be just level with the soil.

Providing Supports

Sweet peas are often left to form bushes and using twigs, pea sticks, netting or trellis to support them, they make very colourful displays throughout the summer. "Wigwams'' and rows are the most common arrangement. The plants can be gently tied into the supports, but will soon use their tendrils to grab each other and the support in order to climb. Water well, especially when the plant is in full flower, use a liquid feed from mid-summer at about fortnightly intervals. Dead-head the plants regularly to encourage more flowers.

Training for Exhibition Quality Flowers

Exhibitors use a method called cordon training. This produces fewer flowers but they are top-quality. Set up two 2m posts with a taut wire stretched between top and bottom. Anchor the ends of the wire tightly around the posts. Firmly attach a 2.2m (7ft) cane to the wires and push well into the ground at 22cm (9in) intervals. The rows should run north to south to give the plant even sunlight. Leave the plant a couple of weeks after planting to establish, then remove the weakest shoots, leaving the strongest shoot. This one can then be trained up the cane. Tie the shoot using raffia, tape or rings at each leaf joint or node. Remove any side shoots, tendrils or any flower stems with less than four buds. When the plants reach the top wire or the top of the cane, untie each plant carefully and lay it along the ground to its full length. When all the plants are untied, attach the shoot tip to a new cane further up the row, so it reaches about 30cm (1ft) up the new cane. Tie it in as before, and repeat for the other plants. New flowers will be produced by the plant being stimulated by the layering process.

Pests and Diseases

Keep an eve out for greenfly, whitefly, caterpillars and other pests, if they become a problem, use a recommended proprietary brand of insecticide. Mildew can, in some years, become a problem. Try to avoid watering from above. Pick off any badly affected leaves and spray with a recommended proprietary brand of fungicide. Deadheading will promote more flowers and help reduce the spread of any pests or disease.

General Care

Keep the plants regularly watered and feed with a general all-purpose liquid fertiliser every 10 - 14 days. When the plants are in flower, a regular feed with a high potash feed (most tomato feeds) will also benefit them. Don't forget to deadhead and remove any damaged flowers or leaves.