Choosing fertilizer for flowers, vegetables, trees or shrubs

Reading package labels of fertilizer for flowers, vegetables, trees or shrubs may raise more questions than it answers. The label on a time or slow release product says it will work on your plants, but so does the label on a water-soluble product. And then, there’s organic fertilizer. So what’s the difference?

Breakdown by fertilizer type
  • Organic fertilizers can include manure, compost or leaf mold. Compost can be made from chopped vegetables, fruit and egg shells from the kitchen and plants, grass and leaves from the yard. Decaying leaves become leaf mold. Organic material is always a good choice for anything that you are planting because of the beneficial microbial activity introduced into the soil.  
  • Time release fertilizers may be in loose granular form or as a spike that is inserted into the ground. Each form gradually disintegrates, releasing nutrients with rain water. You choose the duration of fertilizing based on the plant. For instance, flowers and vegetables would use a 3 month time release fertilizer while trees, especially fast growing trees like Leyland Cypress, could use up to a 14 month time release fertilizer.
  • Water soluble fertilizer may be powder or liquid form and is meant to be dissolved in water for application through a garden hose attachment or sprinkling can. 
Breakdown by vegetation

Manufacturers of fertilizer for flowers, vegetables, trees or shrubs make formulas that are suitable for multiple types of plants as depicted below. The set of three numbers is the percentage of nitrogen, phosphorus and potassium the fertilizer contains.

Acid-loving plants. As an example of a multi-function fertilizer, Scotts Miracle-Gro offers a single product for azalea, camellia and rhododendron. Read the small print on the package and you will see this type of fertilizer is good for all acid-loving plants like dogwood, magnolia, gardenia, orchid and all evergreens (tree or shrub). Fertilizers developed specifically for acid-loving plants may be time release or water soluble and have a formula like 30-10-10.

Deciduous trees and shrubs. Deciduous (sheds leaves each year) fruit, shade and ornamental trees and flowering shrubs like spirea and lilacs can use a time-release fertilizer with a formula like 15-10-9.

Vegetables and Flowers. An “All Purpose” plant fertilizer can be used on vegetables, annual flowers and perennial flowers. An all purpose fertilizer could have a formula like 24-8-16. Because of the frequency with which flowers and vegetables need to be watered, a water soluble fertilizer could be the best choice.

Time release versus water soluble fertilizers

Whether you use time release or water soluble fertilizer for flowers, vegetables, trees or shrubs is a matter of personal preference and what you are willing to pay. A 3-pound container of Osmocote four-month time release for flowers and vegetables costs about $12 (Lowes) and covers about 120 square feet. A one-quart container of water soluble Miracle-Gro for flowers and vegetables (all purpose), which is applied every 2 weeks, costs about $6 (Lowes) and covers 960 square feet. Though the water soluble variety requires more frequent applications each growing season than the one-application slow release fertilizer, the water soluble solution is cheaper.