Deep, infrequent watering is preferred over frequent, light watering. Slow deep watering allows the soil to become thoroughly moist and encourages a deep root system. The amount and frequency will depend on natural rainfall, soil types and the types of annuals grown. Generally, applying about one inch of water per week is sufficient. If it is possible, water early in the day to allow the foliage to dry off before nightfall. This helps to prevent or minimize disease issues.
Most annuals will do well with the basic initial fertilization during soil preparation. Any check in growth caused by insufficient nutrients or water can reduce the quality of the planting. Additional fertilizer application can be made 6-8 weeks after planting if the appearance of the plants requires it. Apply about one-quarter to one-half the recommended bed preparation rate (1-2 pounds per 100 square feet) of fertilizer to the planting bed. If dry fertilizer is used, follow the application with water to remove fertilizer from the foliage. Liquid fertilizer is also an option and it should be applied to moist not dry soil.
After annuals are planted, a 2-3 inch layer of organic mulch may be applied. Not only is it attractive but it also helps to conserve soil moisture, retard weed growth and helps keep soil cool. Mulch materials such as dry grass clippings, hulls, pine needles, compost or shredded leaves are acceptable. In the fall, these materials can then be worked into the soil to help add organic matter and improve the soil structure.
It is essential that weeds be controlled while small and as they appear. Weeds will compete for space, moisture, and nutrients with the annuals. Remove them with shallow cultivation. Mulch added afterwards will help retard future weed growth. As annuals get larger and start to fill in and shade the soil surface this will also help to slow down the growth of weeds.
Many annuals require little additional care to keep them attractive and blooming all summer. However, some annuals benefit from deadheading or the removal of spent flowers to encourage a strong rebloom. Annuals such as geranium, marigold, salvia, cosmos, snapdragon and other spike type flowers benefit from the removal of old flowers. Deadheading will help the plants remain attractive, keep them from going to seed, help prevent disease and increase flower production. Deadheading can be done by either pinching out the old flowers as they fade with your fingers or cut them out with a pruning shears.
Most annuals need no deadheading as they are “self-cleaning” meaning the old blooms fall off naturally and do not require the manual removal of old flowers. Annuals such as begonia, petunia, impatiens and vinca are examples of “self-cleaning” annuals.
Pinching is the removal of the growing tip of a plant in order to encourage more branching and a shorter, fuller plant. Pinching will encourage more branching at the base resulting in more bloom potential. It is a good technique to employ mid-way through the season to help restore
plants to a more attractive shape. Petunias are a good candidate for this especially if they have gotten tall and floppy in the garden or baskets have started to lose their appeal. Pinching is good to do at any time you feel the need to groom a plant. The results will be a plant with a better shape and often a more youthful appearance.
While hard to do, pinching off the blooms of new transplants when setting them into the garden results in bushier plants with more flower potential as the season progresses. If your transplants are tight and compact to begin with there might not be any reason to pinch them. Many of the newer hybrids display a short compact growth habit. Use your judgment but remember to not be afraid to pinch.