Lathyrus X odoratus: Sweet Pea
Sweet peas are favouritein gardens as well as for the balcony and window-boxes.
Some 160 species have been described to date. The one selected for cultivation for its fragrance as well as the lovely shape and colour of theis native to southern Italy and Sicily. Because it has been grown for as long as 250 years, its hybrids are many, divided into several groups according to habit of growth, number of flowers on the separate stems, and height.
Tall forms are either cultivars belonging to the Spencer group (such as ‘Flagship’ — dark violet) or the large-flowered and multi-flowered Cuthbertson cultivars (such as ‘Jimmy’ — dark scarlet). More important for our purpose (even though robust plants may be suitable for terrace decoration) are the low-growing sweet peas, suitable for window-boxes. Though the flowers are smaller and not as good for cutting as those of the tall forms, these plants are only 20 to 30 cm (8 to 12 in) high. There is no point in naming the various cultivars for quite a few have been developed in Britain and the USA. They are generally offered in a mixture that includes all shades and colours except yellow.
Window-boxes in which sweet peas are to be grown should be filled with a heavier, rich and at the same time freely-draining mixture such as John Innes potting compost No. 2. Though the seeds may be sown and the plants grown-on indoors, it is better and easier to sow them directly in the window-box in late March. It is recommended to sow them at 14-day intervals so as to prolong the flowering period. The flowers, which appear from June onward, should be removed as soon as they have faded to prevent the formation of seeds, otherwise flowering soon ceases. Feed should be supplied the whole summer long.