When to Fertilize Raspberries

Fertilizers

• In general, 10-10-10 fertilizers work well for raspberry bushes. However, if you want to determine the exact deficiencies that require supplementing in your soil, collect a soil sample for testing. Many university extension offices provide the service for free. If you prefer not to use fertilizers in your garden space, you can instead use horse, pig or cow manure to treat raspberry bushes, the Iowa State University Extension advises.

After Planting

• New raspberries bushes require fertilization twice in the weeks after being planted. First, apply 1 lb. of a 10-10-10 fertilizer to the soil for every 100 feet of row space 10 days after planting, the Ohio State University Extension advises. Repeat the application again 40 days after the bushes were planted.

Established Bushes

• Starting in the second year, raspberry bushes need annual fertilization, ideally in the early spring. Apply 20 lb. of a 10-10-10 fertilizer for every 1,000 square feet of planting area each year. The University of Maine Extension recommends splitting the fertilization into two applications: one in early spring and then another four to six weeks later.

Fertilizing Tips

• If your raspberry plants are covered with a heavy mulch, consider increasing the application rate to 25 lb. for every 1,000 feet or garden space, the University of Maine Extension advises. Also, avoid fertilizing raspberries in summer or even late spring, because it promotes late-season fruit growth, which in turn can make the plants more likely to suffer cold damage during the winter.