In Britain plants are usually grown to bloom from the beginning of April onward till the out-of-door flowers are ready, and it can with perfect truth be said that as fine flowers can be grown in this way as out of doors; The usual standard sorts are grown. In the Gardeners' Chronicle of September 5th, 1914, Mr. Andrew Ireland, Messrs. Dobbie & Co.'s expert grower, who has had remarkable success in growing Sweet Peas under glass, tells the method he follows in the following words: -
"The seeds should be sown in boxes or pots at the end of September, or early in October, and allowed to remain in a cold frame or a sheltered corner out of doors, until after Christmas. By that time they will be hardy little plants, possessing plenty of roots and ready for potting on into small sixty sized pots. When they are potted they should be grown in a greenhouse or close frame. It is surprising how quickly they commence to develop, and at this stage care in watering and airing are the principal requirements. They should be grown under a cool treatment, for if coddled they make weak spindly growth. In six or eight weeks after potting, they should be shifted into their flowering receptacles, whether pots, boxes or tubs, or they may be planted in the border of the house. The most suitable compost is formed of good loam, a little decayed stable manure, sand, bone meal, and a dusting of soot. In this mixture, the plants will grow well until they reach the flowering stage, when the roots should be fed with manure water twice a week. If large blooms up to exhibition size are required, the plants should be thinned to two or three shoots and then staked and tied. The main growths can be trained into any shape, and when they have reached the top of the house they can be untied, bent, and thus brought down to within three or four feet of the ground without injury. The variety Mrs. Cuthbertson has grown twenty-two feet long, being taken down from the roof when necessary. Such a plant will produce fifty to sixty good flowers on each growth.
Treated in this way a long season of first-rate flowers with long stems is assured. If grown in pots, tubs or boxes for decoration, the shoots may be trained on a framework, or Simplicitas netting, which makes a neat, tidy support and will last for several years. A mulch of short manure will help to prolong the flowering season. Sweet Peas are seen at their best under glass, for rain, sun or wind cannot damage them. The following varieties are best for glass culture - Charles Foster, Lady Miller, Melba, Lavender George Herbert, Elfrida Pearson, King White, Thomas Stevenson, New Marquis, Wedgwood, Edrom Beauty, Dobbies' Scarlet, Dobbies' Cream and Mrs. Cuthbertson."
The number of plants put into the flowering tubs or pots depends on how they are going to be treated. If to be disbudded, three or four plants must go in a ten or twelve-inch pot. If they are to be allowed to grow naturally, two good plants are enough.