What to feed your raspberry plants

ripe raspberry ready to be picked

While most raspberry (Rubus spp.) cultivars are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 7, their temperature tolerance varies by variety. Recommended raspberry varieties for Wasilla include Latham, Boyne and Fall Gold. One thing all raspberry plants require, whether grown in Wasilla, Alaska or Westbrook, Maine, are the right nutrients at the right time.

What to feed at planting

Choose from a variety of products with which to amend the soil when planting your raspberry plant. Organic gardeners may want to use a well-rotted manure or compost, at a rate of 2 cubic yards per 100 square feet of planting area. Not only do these materials add nutrients to the soil but they improve drainage as well. If you aren't growing organically, use 1 cup of balanced organic fertilizer such as 3-3-3, and 1/4 cup kelp meal. Whatever you choose, blend the materials with the top 4 inches of soil.

First-year raspberry plants

Appropriate care of the raspberry plant during its first year is critical to its future production. While it may not bear fruit in the first year, it is collecting nutrients to build strong canes.

Although a rule of thumb is to not fertilize the plants during the first year, it’s important to base that rule on how much the plants have grown. Canes that grow to 4 to 6 feet in height are receiving enough nutrients. If, on the other hand, the canes are only growing to 3 feet tall, apply .5 ounce of 16-16-16 fertilizer. This fertilizer includes the three primary macronutrients -- nitrogen, phosphorus and potassium. Sprinkle the granules around the bush, keeping them at least 3 inches away from the base of the plant. Water the plant -- to the depth at which it was planted -- after the application.

Annual needs

In spring of the raspberry plant’s second year, before new growth appears, apply 10 ounces of 5-4-3 fertilizer. This fertilizer is higher in nitrogen, which helps promote foliage growth. The second number represents the percentage of phosphorus in the fertilizer, which promotes flowering and fruiting.

Potassium, represented by the last number in the fertilizer analysis, plays a number of roles in the life of the raspberry plant, from regulating water intake to affecting the color, size and taste of the raspberries. Sprinkle the granules around the raspberry plant and use a rake to lightly scratch it in to the soil. Water as you normally do after the application. Provide another application of the fertilizer a month later and again a month after that.

Fertilizer precautions

Fertilizer that washes into area lakes, streams and rivers causes overgrowth of algae that can end up killing fish. Use caution when applying fertilizer to the raspberry bush so that it doesn’t end up in a storm drain or drainage ditch. Don’t fertilize on a day when heavy rain is expected to avoid fertilizer run-off into gutters, waterways and drains. Sweep up any granules that spill onto the sidewalk or driveway.

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