Sweet-peas should be sown in autumn in order to obtain an especially early crop, but unfortunately this cannot be done in damp or heavy soils. The directions given for spring sowing will, of course, apply equally to that in autumn.
For growing the seedlings under glass, pots or boxes must be got ready, first cleaning and crocking them, and then filling with good light soil. Not more than six or eight seeds should be sown in a 5-inch pot, and these should be dibbled in evenly an inch below the surface. Water the pots lightly, and place them in a cool greenhouse. This is preferable to a cold frame, but if there is no greenhouse a frame will serve.
The pots should be kept as close to the glass as possible, otherwise the young plants are liable to become weakly and drawn. If space is available, excellent results should be obtained by dibbling single seeds into "thumb" flowerpots, and potting the plants on; but this will not always be thought worth while. Give all the air possible to the young seedlings, taking care to avoid frost at night. Sweet-peas should never be coddled if they are to be strong and healthy when the time comes for planting-out.
Planting should be done by the middle of April, in an open, sunny situation, and in soil which has previously been well prepared. It is foolish to attempt to grow sweet-peas in ground which has not been deeply dug and thoroughly manured. This should be done in the previous autumn, or else in early spring. As each trench is taken out, a thick layer of well-decayed manure (farmyard or cow manure being used for choice) should be laid at the bottom' of it. Some good fibrous loam should be incorporated with the soil in which the plants are to be put, and a dressing of lime underneath will be beneficial. Leave the ground rough after trenching. It should be pricked over with a fork immediately before sowing, and the larger lumps removed.
Put in the little plants carefully, either in round clumps or else in rows, according to the scheme desired. Give a good watering, and encourage the seedlings to attach themselves to the twigs of birch or hazel which should be placed among them, and which will be rather taller than the little twigs already used for staking the tiny plants while in the greenhouse.
As soon as they approach the top of these, the stakes should be inserted. These should be 6 or 8 feet in height, and be placed on the inner side of the clump or row. For a clump of sweet-peas, the branches are put in in cage-like form, leaning towards each other at the top, and should be cut off neatly with a knife or secateurs. Two or three ties of tarred string will make the cages neat and secure. Special sweet-pea supports, made of galvanised wire, can be obtained for use, instead of the natural stakes, if preferred, or wide-meshed sheep wire can be bought for the purpose at any ironmonger's.