All annuals need caring for in different ways and we will care for them appropriately. However, general rules apply for caring for perennials and I have outlined these below:
Annuals have a far shorter window of opportunity to flourish than perennials so a gardener should focus on them and make sure they reach their full potential during their short lifespan. Annuals are typically less hardy than perennials; their specific requirements need to be met. It is a good idea to follow the instructions of a good gardening book in order to know how to care for each type of annual but general standards of care must be met and I will outline these below.
Hardy and Half-hardy annuals
Annuals can be hardy or half-hardy. Hardy annuals are able to tolerate periods of frost. In contrast, half-hardy annuals tend to be incapable of living through periods of frost. Hardy annuals and half-hardy annuals should be cared for differently. Half-hardy annuals should be raised in a greenhouse or cold frame and planted out after the threat of frost has subsided. Hardy annuals, on the other hand, can be sown directly into their desired location.
Sunny, sheltered locations are ideal for annuals.
Annuals should be watered regularly, until they are established. It must be noted that annuals have shallow root systems, so unlike many perennials they cannot obtain water from deep within the ground. Annuals need to receive approximately 1 inch of water, via rainfall or irrigation, every week. They need to be watered during periods of drought, otherwise they could fail to thrive or even die.
Annuals should be raised in fertile soils so that they can develop well and become a focal point for the garden. Exactly the right quantity of fertilizer should be applied. Annuals should not be over-fed as overfeeding can result in vigorous vegetative growth and limited flower production. Slow-release fertilizers can be used in order to provide annuals with nutrients throughout the growing season. The slow release of nutrients avoids the damaging effects of overfeeding. Exactly the right quantity of fertilizer should be applied as if too much fertilizer is applied they may grow too quickly and produce fewer flowers.
If annuals start to flag, mid-season it is a good idea to apply some liquid feed to bring them back to life.
Weed Killing and mulches
Weeds compete with annuals for water, light and nutrients so it is important to control them. It is better to controls weed by hoeing and mulching rather than using weed killers because weed killers can endanger other plants.
Mulches can be applied around annuals to help maintain water within the bedding area and to suppress weeds. Organic mulch, such as bark or compost, adds nutrients to the soil as it breaks down.
Tall annuals may need staking, especially if positioned in a wind area. Alcea or Helianthus are tall plants so they often need staking. Annuals in containers may be supported using canes. Canes should be put around the diameter of the pot. Soft string, can then be put around the canes to hold the plants in.
Most annuals should be dead-headed in the same way as the majority of perennials. This encourages new flower growth to emerge, as the plants put energy into re-establishing themselves. However, some annuals such as Papaver will not produce more flowers after dead-heading.
Do not dead-head those annuals that have attractive seedheads, as they will enhance the appearance of the garden. Hibiscus trionum and Zea mays are plants that fall into this category.
Clearing the Bed
After the flowering season annuals should be cleared away, once any seeds that one wants to retain have been taken. Diseased plants should be burnt so that they do not spread their infection.