True annuals are plants that will complete their life cycle within twelve months of sowing. Biennials require two growing seasons to do so and are usually sown in summer to flower during the following spring and summer.

Many other plants that botanists would define as perennial can be treated as annuals, although some are half-hardy and, while able to flower well for a single season, are not hardy enough to be used for more than one year. Half-hardy annuals are generally raised in a greenhouse, then 'pricked out' (transplanted, a few centimeters apart in larger boxes) and grown under protection before being planted out.

The winter hardiness of biennials depends on the district where they are to be grown. But there are significant advantages in planting out in late summer or autumn for all those hardy enough to winter well. For example Canterbury Bells that are planted outside as transplants in the autumn will flower well the following summer, but if planted out in the spring they tend not to flower until twelve months later!! Sweet Williams behave in a similar way.

Biennials are usually sown in a seedbed in the open, or in boxes in a frame or greenhouse, and transplanted as seedlings. They are then put in their final quarters in late autumn, as in the case of Wallflowers which do best in cool regions. It is quite important to plant out forget-me-nots and cinerarias in the autumn, as both of these flower early and therefore need to be planted out well ahead of flowering time.

Cinerarias are suitable only for areas free from frost but in such areas they are very showy and they are particularly useful for shady gardens. There are short, medium and tall types and the color range is wide. Especially good are the rich blue shades.

Plants that are not frost hardy include Begonia semperflorens, coleus and impatiens. The latter have become extremely popular plants. They are available in both short and taller varieties and also in numerous double flowered cultivars, which are mainly propagated by cuttings. Impatiens grow well in full sun if watered or in shade and are popular container plants for patios.

Hardy biennials are plants that are sown the year before they are expected to flower. They are raised in a seedbed outdoors or in a cool, shady frame and may be thinned out or transplanted when large enough. For best results planting out should be done in the autumn. If they are bought from the garden center in punnets or seedling trays, plant them out early in the season. Even in areas where the winters are mild, planting at that colder time will result in small flowering plants, except perhaps with pansies and violas.

Annuals that can be sown directly in well prepared flowerbeds and which come quickly into flower are bound to be popular if they are capable of sustaining flowering for a lengthy period of time. There are numerous suitable varieties to choose from and in most cases they may be sown in boxes and transplanted. Before sowing time, prepare the growing site. If the soil is lumpy and heavy, compost should be worked in and planting mix applied to the surface. Then choose a dry day, apply a little general fertilizer and rake it in. Seed can be broadcast or it can be sown in shallow drills.

Some seedlings can be safely transplanted but the following do not transplant easily: clarkia, eschscholzia, godetia, gypsophila, linaria, nigella and poppies.

Half hardy annuals must be raised in a frame or greenhouse or in a few cases sown outside after the danger of frost has passed.

Germination time varies, and most kinds require pricking out into boxes or pots of potting compost. Some of the seeds such as lobelia, begonias and petunias are very small and need to be sown carefully and kept out of direct sunlight.

Nowadays the numerous garden centers often do all this work for you offering a good range of these plants n punnets ready for planting. But it may be that you want to use seed collected from your own garden, or wish to grown varieties unavailable in punnets. In any case you will find that raising your own seedlings can add a great deal of interest to your garden.

Michael Russell

Your Independent guide to Gardening