You can fertilize blueberries and blackberries soon, but they are not in bloom yet, which is when applications are best made.

Blueberry plants prefer the ammonium form of nitrogen (N) instead of the nitrate form. An N-P-K of 21-0-0 (ammonium sulfate) is an excellent synthetic fertilizer for blueberries. Fertilizers formulated for “acid-loving” plants are also suitable. Organic fertilizers can be substituted. Avoid fertilizers containing high percentages of nitrates or chlorides.

Do not fertilize the first year after planting. In the second year, apply 2 ounces of 21-0-0 (ammonium sulfate) per plant during bloom, and the same amount again 3 weeks later. Scatter each fertilizer dose in a ring 12 to 18 inches from the plant. Third-year and older plants can have their fertilizer dose increased by 1 ounce per year, each year, until the sixth year they've been in the ground. Then, use a fertilizer dose of 8 ounces total per plant each succeeding year.

Acidic soil helps blueberry roots access the nutrients they need. If the soil is not acidic enough, nutrient supplementation will go largely unused. Aim for a soil pH of 

For blackberries, pH is not as critical and they thrive in the 6.0 to 6.5 range. Fertilizer for first- and second-year plants uses .80 ounces of nitrogen (N) per 10 feet of row at flowering. Third-year and older plants can double this, to 1.6 ounces of nitrogen (N) per 10 feet of row at flowering.

Miri

Hello Jim,

Any type of fertilizer that contains nitrogen can provide that nutrient (organic or synthetic, liquid or granular, etc.), and the application dosage will determine the fertilization rate. You can visit our Garden Fertilizer Basics page to see examples of nitrogen (and other nutrient) forms and the Fertilizing section of the Fruit Plant Care page for an example of how to calculate how much to apply of a given N-P-K. (Expand the "using fertilizers" heading.)

Miri

You can use that but don't get it on the trunk or under windy conditions where it could drift to desirable plants.


Christine