Fertilizing Annual Flowers

Growth rate and foliage color are the primary guides for determining the need for additional fertilizer applications during the growing season. However, some general guidelines can be used.

Most annuals do not require high levels of fertilizer, and will do well with just the initial fertilization during soil preparation. However, annual flowers often compete with trees, shrubs, and other members of their own species for moisture, nutrients, and sunlight. Any check in growth caused by insufficient nutrients can reduce the quality of the plant and its bloom.

Nitrogen is the nutrient that most frequently limits initial plant growth. Unfortunately, nitrogen is the most difficult nutrient to manage. Soil tests for nitrogen are not dependable and nitrogen is easily leached from the soil. The challenge is to maintain adequate nitrogen levels to meet the plant requirements without damaging the plants or the environment.

Nitrogen can be applied in a quick-release, water soluble form using a liquid or granular fertilizer or in a slow-release, granular form. Use a quick-release fertilizer (such as 10-10-10), every four to eight weeks throughout the season at the rate of 1 pound per 100 square feet (.5 kg per 9 sq m). Liquid, water-soluble fertilizers should be applied about every two weeks.

With slow-release fertilizers, make only two applications. The first application should be incorporated into the bed just before planting, and the second should be broadcast over the bed midway through the growing season. The total seasonal application of slow-release fertilizer should not exceed 4 to 6 pounds of nitrogen per 1,000 square feet (2 to 3 kg per 90 sq meters).

Flowers require a high amount of phosphorous to produce the colorful blooms that make all your hard work worth while. Phosphorous is the middle number that you see on any package of fertilizer. Use a fertilizer that is specially formulated for blooming flowers. This will give you the best results.

It is recommended that plants be watered prior to fertilizing to insure the plants are actively growing and taking up nutrients.