What Should I Fertilize My Strawberries With When They Are Putting on Fruit?

Purpose

• Fertilizer provides a strawberry plant the added nutrients to grow and develop. Since it has a shallow root structure, fertilizer is especially important to prevent the plant from having to exert unnecessary energy by seeking out nutrients deep below the surface. Improper use of fertilizer, however, can disrupt normal plant growth and result in lower yields.

Timing

• A strawberry plant needs fertilizer twice a year -- once during their growing season and again before buds form. The first application usually takes place mid-summer in either June or July, at least a month after planting, and the second application usually occurs late summer at some point prior to September.

First Application

• Apply the first fertilizer application to foster bud development just before a plant puts on fruit. Topdress the plant with ammonium nitrate, 1 1/2 lb. per 100 ft. of row. Take care when using this application to uniformly spread fertilizer around the entire plant without getting it on the foliage. If fertilizer gets on the plant's leaves, wipe it off immediately to prevent leaves from burning. Once the fertilizer has been applied, irrigate the plant immediately, so the fertilizer quickly penetrates the soil and roots can benefit from it. Nitrogen strengthens a plant and helps its roots absorb moisture and nutrients faster, thus encouraging fruit formation.

Second Application

• The second fertilizer application is done before renovation begins. Renovation involves cutting down a plant to its base to eliminate old foliage, so new leaves and stems form next season. Apply 4 lbs. of 10-10-10 nitrogen, phosphorous and potassium (NPK) fertilizer or 1 1/2 lbs. ammonium nitrate per 100 ft. of row -- at the same rate, and using the same application method used for the first application. Irrigate it soon after the fertilizer is applied, so the fertilizer seeps down into the soil more rapidly where roots can access it.

Implications of Overfertilization

• Although a strawberry plant needs fertilizer to grow and produce fruit, too much fertilizer can harm plants. In particular, excess nitrogen can lead to quick vegetation growth, but also inhibit fruit set. Unless a plant shows signs of nutrient deficiency, such as stunted growth or pale green foliage, don't treat it with another fertilizer application, in addition to the two required for a healthy plant. A third fertilizer application is generally only warranted when the plant shows signs of extreme stress.