Annuals live to flower quickly, produce seed and die. Pinching off spent blooms is quick and easy, and it ensures season-long bloom. If you ve fertilized at planting time as recommended with an organic or slow-release fertilizer, you shouldn t have to fertilize annuals again during the season. With annuals, the flowers are the thing, and overfertilizing can lead to lush foliage growth, which is really beside the point. The primary exception is container-grown plants, which usually need to be fertilized every couple of weeks to maintain a colorful show.
Annuals have small, shallow root systems and so require a regular supply of water.
It also can contribute to a buildup of botrytis fungus, which can affect plants such as zinnias, geraniums, and marigolds. For best results, use a soaker hose or other drip irrigation system, or direct your watering can right at soil level.