When & With What Do I Fertilize Blueberry Plants?

Type of Fertilizer

• Use rhododendron or azalea fertilizer, as they love acidic soil just like blueberries do. Balanced (10-10-10 or 20-20-20) fertilizer is best. Blueberry plants are especially sensitive to nitrogen. In fact, nitrogen-rich fertilizers will hinder flower and fruit production in most cases. An exception to this rule is if the soil is high in phosphorus. In that case, use ammonium nitrate instead of a balanced fertilizer.

First-Year Plants

• First-year plants have different fertilizing needs than mature plants. Do not fertilize blueberry plants right after you plant them. Instead, wait until the leaves have uncurled and reached their full size. Then, sprinkle just 1 tbsp. of the balanced fertilizer, or 1/2 tbsp. of ammonium nitrate, in a circle around the plant, about 12 inches from the stem. Do this every six weeks until August. Make sure the plants get at least 4 inches of water between each period of fertilization.

Mature or Fruit-Bearing Plants

• Mature blueberry plants (those that have borne fruit) should be fertilized differently than newly-planted bushes. In the spring, when the leaves appear, fertilize with 1 cup of a balanced fertilizer within an area 3 feet around the bush. Then, apply 1/4 of a cup of ammonium nitrate every six weeks to the same area. Do not fertilize any more after July 1st. Fertilizing after this time will encourage late autumn growth, which means the plant could be damaged by freezing winter temperatures.

Other Considerations

• Blueberries should not be allowed to produce fruit for the first two years, according to the University of Maine. So, follow the procedures for fertilizing newly-planted bushes for at least two years. In addition, remove the flowers in the spring. This will allow the plant to develop a vigorous root system, which will make it much more impervious to diseases. Leave a few flowers on the third year and allow the blueberry bush to produce a small amount of fruit. Again, fertilize it according to the plant for newly-planted bushes. After the third year, fertilize according to the plan for mature bushes and let the plant produce a full crop of blueberries.