Garfield County Cooperative Extension

Annual flowers require fertilizer early and often for optimum color

Rick Nelson Extension Educator, Ag/4-H

Brightly colored annual flowers are popping throughout the area. Annuals are an easy way to provide color with little care and you’ll get the most from your plants if you give them a little attention. Here is what you need to know to achieve best results.

Know how buds form

Annuals have a limited time to flower before frost puts an end to the color. The goal is to get as many flowers as possible in that short period of time. Breeders have been working hard to simplify the process, but the plants still need assistance. Blooms form at the end of a healthy, vigorous vegetative shoot. The biggest, most robust plants are those that produce a lot of new green growth in which the flowers form. So your goal is to produce more of that green growth, which means feeding your plants consistently and often. Many times annuals underperform because they are not fed enough to push the growth. The secret to fertilizing annuals is to keep it up all season long.

Start at planting. This application helps the plants get established. To keep them growing strong, feed them monthly through September.

More nitrogen, less phosphorus

Marketers of plant fertilizers have not always based their information on sound soil fertility research. Many flower fertilizers have higher amounts of phosphorus and lower levels of nitrogen. With names like “bloom buster,” these products miss the research-based point that flowers are produced from new green growth.

While phosphorus is important, it is associated with root development, not flower bud formation. Look for the three numbers on the product label. If the middle (second) number of the three is the highest, then put it back on the shelf. The first number in the nitrogen, phosphorus and potassium ratio is the most important: Nitrogen is responsible for green shoot development.

Fertilizers labeled for flowers are not always properly formulated or easy to use, and they may not provide the best results.

How to fertilize

The problem for many gardeners is fertilization involves math and soil chemistry. Most of us just want simple, clear directions. If you have not had a proper soil test, which provides all the information you need, here is the recipe for flower fertilization.

Once a month evenly spread a fertilizer such as 10-10-10 or something similar at the rate of 1 pound, about 2 cups per 100 square feet of bed area. Estimate your square footage by multiplying length times width. For small plantings of five or six annuals, sprinkle 2 to 3 tablespoons of fertilizer over the area. Be sure to water it in after the application. This formula is easy to follow and inexpensive.

Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Oklahoma Cooperative Extension Service is implied.


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