What to do First
Sending plants by post may cause them a little stress, so unpack them immediately and, if dry, stand the trays for a few minutes in a suitable depth of water, until the compost is moist again. You may notice a slight yellowing of the foliage or that plants look a little drawn but this is quite natural after they have been in a dark box and they will soon recover.
After you have checked them stand them in a bright, airy position until you are ready to plant. This can be a sheltered place outdoors, if the weather is mild, or in a cold frame, a cool/cold conservatory or greenhouse, a well-lit porch or even on the windowsill of an unheated room. Wherever you place them, avoid keeping them under warm conditions or exposing them to direct burning sun through glass.
Planting Them Out
Your plants have arrived ready for planting and, although they may be left for a few days, as described above, they should otherwise be set out in the garden as soon as possible.
Aim to plant out on a dry day when the weather is reasonably mild and the soil is free of frost and not excessively wet. Every effort is made to send out plants at the correct time for planting but, if weather and soil are not suitable in your area at the time of arrival, planting should be postponed for a short while until conditions are more favourable.
Any good, well-drained soil, free of perennial weeds and which grows other flowers and vegetables well will also grow good sweet peas. The site should be an open and sunny one but preferably with some shelter from north and east winds. Try to plant on land that was dug and manured the previous autumn as sweet peas like firm and settled soil conditions.
In preparation for planting it will be necessary to erect a suitable system of supports for your plants unless you are planning to grow them against an existing structure such as a trellis or chain-link fence. Wigwams of canes are ideal where space is limited. Otherwise bean netting or a double row of canes can be used. Whatever support is used, it should be remembered that sweet peas will grow to 1.8m (6ft) or more during a season.
Set out the plants about 20cm (8in) apart, using a trowel. After planting, firm in and water well. Protect newly planted seedlings from slugs and also from birds if they are a problem in your area. We recommend that you do not split the plugs but plant them whole.
To ensure good establishment and growth, water plants regularly in dry weather and give a weak general-purpose liquid feed fortnightly. Unless you are planning to exhibit blooms, it is sufficient to allow plants to grow naturally, only tying in any stems that have difficulty clinging to their supports. Keep a careful watch for aphids.
In order to keep plants in flower over a long season it is important to pick all flowers every 1-2 days. Flowering will be greatly reduced if any seed pods are allowed to form.