Light Requirements
Some annual flowers or plants do best in direct sun, while others thrive in partial shade. A few varieties will handle heavy shade but not many so make sure your annual flower or plant is in the appropriate spot. Take into consideration whether the sunlight is primarily morning or afternoon. Sunshine provides your plant’s energy to grow. Give your annual flower or plant the right sun and they will reward you.
Fertilization
Many of the newly developed annuals bloom hard and bloom long. They need nutrition. Apply a slow release fertilizer in the spring and supplement weekly with a water soluble fertilizer.
Watering
Deep, infrequent watering is much preferred over frequent, light watering. It encourages a deep strong root system. The amount and frequency depend on natural rainfall and the type of annuals grown. The foliage should be kept dry to help prevent foliar diseases. When this is not possible, water early enough in the day so the foliage dries off before nightfall.
Mulching
After annuals are planted, it is a good idea to place a 2-3 inch layer of organic mulch around the plants. Not only is it attractive, but it also helps conserve soil moisture, retard weed growth and keeps soil cool. Some good mulches to consider are compost, shredded leaves, dry grass clippings, bark chips. In the fall, the mulch can be incorporated into the soil adding organic matter and helping to improve soil structure.
Weeding
Weeds should be removed as soon as you see them with shallow cultivation. When mulch is used and the canopy of the flower bed grows closed, weeds should not be a major problem.
Grooming
Many annuals require little additional care to keep them attractive and blooming all summer. Some flowers fall off cleanly and do not need to be manually removed. Others require deadheading. An annual lives in order to produce seed. All its energies are directed toward this task. If you “deadhead” pick the spent flowers before they start to set seed . The plant will have more flowers in an effort to ultimately produce seeds. This practice keeps annuals in the flowering stage longer and usually results in a greater number of blooms. Annuals such as marigold, zinnias, salvia, geranium, cosmos and other spike or single stem flowers benefit from this practice.
To control the growth of some annuals, pinching or the removal of the growing tip is suggested. This encourages more compact growth and a neater habit. The tops of some plants, such as petunia and impatiens, may be cut back 6-8 inches in mid to late summer after the first flush of flowers has subsided to promote a second flowering period in the fall. After cutting, fertilize and water well to encourage regrowth.