What are the benefits of time-release fertilizer?

Time-release, or controlled-release, fertilizer gradually delivers the major nutrients plants need – nitrogen, phosphorus and potassium – over a fixed period. This can range from a few months to a year, depending on the product you choose.

The nutrients are encapsulated in small spheres, called “prills”, made of a resin that dissolves slowly in soil. While conventional fertilizers must be applied regularly throughout the season, time-release varieties need to be used only at planting time. In most cases, additional fertilizers are not necessary.

With time-release formulas, you don’t have to worry about clumping, which can be a problem when granular fertilizers are exposed to humidity. And unlike powder or liquid kinds, which must be diluted in water, time-release fertilizer is ready to use – just distribute the prills within the top 3 inches of soil.

You may apply a time-release fertilizer in almost any garden situation, but it is especially well suited for use with annuals (the life spans of both the product and the plants coincide nicely). Heavy feeders, such as petunias, tuberous begonias and angel trumpets, are the best candidates for this formula. The high cost of time-release fertilizer, however, usually prohibits its use in large-scale applications, such as in vegetable beds.

Read the package carefully to be sure the time-release formula you choose is appropriate for your growing season, and avoid applying it too early. The prills are engineered to dissolve in warm temperatures (generally 70 degrees F and higher). Freezing temperatures can damage the coatings, causing all nutrients to be released on the first warm day.