Hardy annuals are easy to grow and will give a quick and brilliant display provided they are grown in an open, sunny position in any good garden soil. Many annuals are tender and easily killed by frost, so these kinds are sown under glass in the spring and planted out when all danger of frost is over. Some hardy and half-hardy kinds make excellent pot plants for the greenhouse and there are others that need greenhouse cultivation entirely.
Some, such as the nasturtium, flower better if grown on rather poor soil. Most annuals will make too much leaf growth if grown in soil that is too rich or in shady places. Their rapid growth makes them invaluable for the new garden when flowers are wanted the first year, or for filling in gaps in newly planted herbaceous borders. Some, such as trailing lobelias, dwarf nasturtiums and petunias are useful plants for hanging baskets. Many are useful for providing color in urns, terrace pots, window boxes, tubs and other plant containers. Certain low growing annuals find a place in carpet bedding schemes such as are still found in public parks. Although the purist may frown upon their use in this way, a few annuals are suitable for the rock garden.
A number of annuals have very fragrant flowers, as well as rich color. Some have flowers or seed heads which may be dried for winter decoration indoors.
Some annuals, including a number of those used for carpet bedding, are grown for the sake of their colorful foliage.
Apart from removing faded flowers, keeping them weeded and staking the taller kinds they need little attention.
Growing hardy annuals The soil should be broken down to a fine tilth and well firmed before the seeds are sown. Sow in shallow drills or scatter the seed broadcast after previously marking out the position for each group of annuals selected. Cover the seeds in the drills by drawing the soil over them, or rake in the seeds sown broadcast. It may be necessary to protect the seeds and seedlings from birds and cats by placing wire netting or brushwood over the seed bed.
Some hardy annuals may be sown in August or September to flower early the following summer. As soon as the seedlings are large enough to handle they should be thinned. With autumn-sown annuals leave the final thinning until the following spring. Distances apart vary considerably, depending on the ultimate height of the annual, but as a general guide dwarf-growing annuals should be thinned to 10-16cm (4-6in) apart. Those that grow to 38-46cm (15-18in) tall should be thinned to 23-30cm (9-12in) and taller kinds should be thinned to 30-60cm (1-2ft) apart.
If seed is wanted for sowing again next year it is best to mark a few good plants early in the summer The seed heads should not be gathered until they are fully ripe.