A Tasty Task: Fertilizing Blueberries and Blackberries

Boost fruit production with timely fertilizer applications to your berry bushes.

By Kimberly Toscano

Download the Fertilizing Blueberries and Blackberries PDF

Producing juicy berries is hard work. Plants utilize large amounts of water and nutrients to develop those tasty fruits. By applying the right fertilizer at the right time, you can give your berry bushes a helping hand.

When Do I to Fertilize?

Blueberries and blackberries have different needs when it comes to fertilization. Timing of fertilizer applications is focused around plant growth and fruit development. Blueberries respond well to small amounts of fertilizer applied at three separate applications, the first applied when new growth begins in spring, followed by a second application six weeks later. A third application is made just after harvest. For blackberries, apply fertilizer in spring as growth begins and again in June or July following harvest.

What Fertilizer Do I Use?

Most fruit crops require annual applications of nitrogen to support root and shoot growth, maintain healthy green foliage, and promote high-quality fruits. A slow-release nitrogen source is most desirable to prevent excessive losses by leaching in irrigation water. Other nutrients, including phosphorous and potassium, tend to be readily available in well maintained soils. Conducting a soil test is the best way to determine if additional nutrients are needed.

Not all fertilizers are the same. In particular, fertilizers carry nitrogen in several different forms. Blackberries respond well to any nitrogen-rich fertilizer, but blueberries require fertilizers with an ammonium form of nitrogen such as urea, sulfur-coated urea, ammonium sulfate, or cottonseed meal. Any fertilizer sold for azaleas or rhododendrons also works well for blueberries. Avoid using the nitrate form of nitrogen on blueberries, since nitrates have been shown to be toxic to blueberry plants.

How Much Fertilizer Do I Apply?

With nitrogen applications, more is not always better. Too much nitrogen can lead to excessive branching and growth at the expense of fruit production. For blueberries, excess nitrogen can kill the plant. The following table gives application rates per plant for mature blueberries and blackberries. Blueberry application rates increase with the plant age. For first- and second-year blueberries, divide the application rate in half. For third-year blueberry plants, multiply the application rate by 0.75. Apply the full rate to fourth-year plants and older. Blackberries can receive the full amount of fertilizer regardless of age.

What is the Best Way to Apply Fertilizer?

Blueberries and blackberries take up nutrients through their root system. To apply fertilizers, start by gently raking the soil in a circle around each plant. You do not want to damage the roots, so do not rake deeply – simply loosen the surface soil for fertilizer incorporation. Sprinkle fertilizers uniformly around the drip line of the plant and one foot outward, but never near the base of the plant. Be careful not to get fertilizer on the foliage or against the bark because this will cause damage. If the fertilizer does come in contact with leaves, brush it away immediately afterward. Once you have spread the fertilizer, gently work it into the soil with a rake, then water the fertilizer into the soil so it can become available to the plants.

Fertilizing berry bushes does not have to be complicated. Our table makes it easy to determine how much fertilizer to apply and when.

Downloadable PDF for quick reference throughout the year.