The secret to making your flowering trees, shrubs, annuals, and perennials bloom more is in the numbers. All fertilizers have analysis numbers on the package. These numbers represent the percentage of each chemical the fertilizer contains.
For example, 12-12-12 is a typical garden fertilizer that would contain 12% nitrogen, 12% phosphorous, and 12% potassium. The quick explanation is; nitrogen produces vegetative, or top growth, phosphorous produces flower buds, fruit, and root development, while potassium builds strong healthy plants.
Most lawn grasses are vigorous growers and therefore require significantly more nitrogen than the other plants in your yard. A lawn fertilizer would have an analysis of 26-3-3, indicating a fertilizer high in nitrogen. You would not want to use a fertilizer containing such a high percentage of nitrogen on landscape plants because it would be very easy to burn them. You must also keep in mind that many lawn fertilizers contain broadleaf weed killers, and most ornamental plants have broad leaves. The fertilizer doesnt know the difference, and it will damage or kill ornamental trees and shrubs.
During the summer months the growth rate of most plants slows down, and when plants are not actively growing, they need very little nitrogen. Although not vigorously putting on new growth, many plants such as Dogwood Trees, Rhododendrons, and Azaleas are quietly working to produce flower buds for next year. Annual and perennial flowers are also busy making new flower buds.
To encourage flower bud production you can apply a fertilizer that contains a small percentage of nitrogen, a higher percentage of phosphorous, and a little potassium. I recently purchased a liquid fertilizer with an analysis of 5-30-5, ideal for flower production. Because the product is sold as a bloom producer, the manufacturer also added a little chelated iron, manganese, and zinc, all good for your plants as well.
Most garden centers and discount stores carry similar products. I chose a liquid fertilizer because liquid fertilizers are absorbed both through the roots and systemically through the foliage, so they work quicker. I used a sprayer that attaches to the end of the garden hose to apply the fertilizer, but do not use the same hose end sprayer that you use for lawn fertilizers. There could be residual weed killer still in the sprayer.
Hose End Sprayers
About those hose end sprayers. I purchased one that is supposed to automatically mix the proper ratio for you. I used it to apply a general insecticide, and it worked, but it sure seemed like I went through a lot more insecticide than I needed. When I used it for the fertilizer the screen on the little pick up hose inside the jar kept getting clogged with the tiny solids in the fertilizer. I recommend using a solution of one part liquid fertilizer to one part water in the sprayer jar, and applying at a heavier rate.
Watch the liquid in the sprayer jar, and if it isnt going down remove the lid and clean the little screen by spraying it with water from the garden hose. Read the application instructions on the container to determine how much fertilizer to apply, and how often. A fertilizer high in phosphorous will increase flower production. You will see a difference.
Remember the golden rule of applying fertilizers. Not enough is always better than too much.