How to grow Sweet Peas

(Sweet Peas Org) Sweet Peas are actually very easy to grow. You can simply plant them in the soil where you intend them to grow in March or April in the UK (be guided by local weather conditions) and leave them to it. By July you should have flowers. However, to get the best from your seeds you should consider planting them in autumn (late September to early November) or winter (January to February). This will enable you to have stronger and earlier flowering plants.

A summary of the Sweet Pea year :

September/October

Choose your varieties carefully (see Favourite Sweet Peas). Whether you wish to grow varieties for exhibition or for decoration, it pays to select named varieties from the specialist seed merchants – several of whom advertise in the Society's publications. You will tend to get better flowers and you can select your own colour combinations.

In the Midlands and the South of the UK consider planting seeds now.

November/December

You can still plant seeds now but they might need a bit of heat to germinate. You are aiming for strong compact plants so bring them up 'hard.' Keep them in a coldframe (or a cold greenhouse if you do not have access to a coldframe). Don't coddle them and keep the lights open as much as possible. Close and lag if bad weather is forecast.

January/February

You can still plants seeds now. This tends to be the favoured time for growers in the north of the UK. Nip out top two leaves when the seedlings have developed four.

March/April

Time to plant out. Be guided by local weather conditions and not the calendar. However, if the ground is cold and/or very wet it is best to wait. The plants will soon catch up.

You can plant seeds straight in the ground where you want them to grow now.

May/June

Plants will start to flower. Keep the blooms cut – if they set seed flowering will be curtailed.

July/August

Water if the weather is dry but make sure you do this early on in the day to minimise bud drop and to prevent scorching. Feed with a weak solution of your favourite plant food (formulated for flowers) if your plants are starting to look weaker. For exhibition blooms feed preferably before they start throwing blooms with only three florets to a stem.

How to prepare the site:

Much has been written on this subject but the best advice is to be governed by your own soil conditions. Sweet Peas benefit from well cultivated soil and adding a little well-rotted manure or organic compost may be beneficial. Take care not to overdo it though. Heavy soil will benefit from autumn preparation whilst the lightest soils should be prepared for planting in late winter/early spring.

How to sow:

For best results use named varieties or cultivars (see Gallery) in good potting compost and do not overcrowd – plant 1 seed to a 3 inch (8cm) pot or 6 to 8 seeds to a 6 inch (15cm) pot. Place the pots in a cold frame or greenhouse and cover them with newspaper until the seedlings have germinated. If you are planting in January to February your seedlings may need a little gentle heat to germinate. Make sure you stop the heat as soon as germination has occurred, otherwise your plants will get leggy.

Problems with germination? Some varieties have hard coats and may be more difficult to germinate. You could try soaking the seed overnight before sowing (and only sow those that have swollen) or nick the seed’s hard coat by gently rubbing against some sandpaper, on the side away from the 'eye' or scar on the seed. However, most people find that this is not necessary and there is a belief that soaking causes undue stress and weakens the plants.

How to look after your seedlings:

Overwinter your seedlings in a cold frame or cold greenhouse, bringing them up as hard as possible. Take precautions against slugs, snails, mice and birds (and cats who may find them to be a tempting bed). Watch out for bad weather – when frosts are forecast, your seedlings will need some extra protection. Close the frame’s lights and add some lagging (eg newspaper, bubble wrap, sacking etc). If the weather is particularly cold or the frosts prolonged, leave the lagging on to allow the seedlings to thaw slowly. When the first four leaves have formed, nip out the top two leaves to encourage bushiness. Do not forget to keep your plants moist if the weather is dry.

How to plant out:

For plants you wish to grow using the cordon method plant out your seedlings 8 to15 inches (20 to 38cm) apart in rows in March or April (in the UK) in your previously prepared site (see How to prepare the site). Each plant will have its own cane to grow up.

If you want to grow your plants naturally (termed 'on the bush') set plants 8 to12 inches (20 to 30cm) apart and give them something to scramble up such as a fence with pea net, or a wigwam of canes with some string or raffia for the tendrils to catch on to. Do not forget protection against slugs, snails and birds if they are a problem to you.

Sweet Peas perform best in an open sunny site.

How to look after your plants after planting out:

Well hardened off plants should not require any further protection unless the site is particularly exposed. Let the plants get on with things themselves for about 4 to 6 weeks. If you are using the cordon method restrict the growth to the strongest shoots and tie in to the support. If you are growing your plants naturally, encourage the small plants to cling to the support by tying in at first and spreading out the shoots over the support. If your plants are particularly bushy you may have to remove some shoots to prevent overcrowding.

Make sure your plants do not suffer from lack of water but remember not to water during the hottest part of the day. Extra feeding probably will not be necessary if your soil was well prepared.

Enjoy the flowers which should start to appear from late May to early June. To prolong flowering ensure that the flowers do not set seed, take the flowers into the house and enjoy their scent.

How to grow using the cordon method:

This is the method favoured by exhibition growers and anyone wanting to grow top quality flowers. It requires more time with a commensurate improvement in blooms. You will find that you will have fewer flowers using this method than growing naturally but they will be of much better quality.

After planting out leave your plants for around 4 to 6 weeks to settle. After this time, depending on the local weather conditions, they will probably be at least 12 inches (30cm) tall. Restrict the growth to one shoot by cutting or nipping out the extra shoots and tie the remaining shoot loosely to its support. You might want to use metal rings to tie in your plants as these tend to be quickest overall but anything will do. Continue to nip out side shoots which form at every leaf axil, tying in the plant as necessary. You should also remove the twisty tendrils seen at the end of the pairs of leaves which form up the stem. It is rather like growing tomatoes on the cordon. Do not allow flowers to set seed. Most growers cut them as they open which means one stem per plant every day or every other day, depending on weather conditions. Many growers will also nip out the early blooms as they form to further strengthen their plants, doing so until the blooms start to form with four florets per stem or until June.

Growing on the cordon means that all the plant's energy is concentrated into producing better flowers and growth of the single branch. This means that your plants will soon reach the top of your canes. You will then need to 'layer' them. Do not confuse this with propagation – all this means is to drop your plants down to the bottom of the canes so that they can grow up again. You may need to do this more than once during the season. The easiest way to layer is to undo the ties and gently lie your plants horizontally along the rows. They will naturally turn upwards in a day or two and you can then tie them in to the nearest cane and continue as before. You may choose to tie train them up a cane further along the row straight away. Take care not to snap the plant as they can be very brittle. Choose a warm day and make any bends gradual.

Common Pests and Diseases

Mice are the greatest danger to the seed during the period of germination. Later on, watch out for birds, slugs and snails.

Aphids transmit mosaic virus. Plants start to grow poorly and have speckled leaves and flowers. Pull out infected plants to prevent the disease from spreading.

Bud drop – every Sweet Pea grower experiences this at some point in his or her growing career! In periods of cold weather the developing flowerbuds may turn yellow and fall off. Some varieties are more prone to this than others.

Leaf Scorch – leaves lose colour from the bottom upwards and dry off or 'scorch' but the plant continues to flower until the top leaves are affected.

Pollen beetles – Vast numbers of these small black insects can accumulate in the blooms, particularly on lighter coloured varieties. There is no chemical control available so the best advice is to place vases of affected flowers in a dark room with a light source at one end. The beetles will be attracted to the light and should abandon the flowers.