How Do I Fertilize Blueberries with Black Gold Fertilizer?

“I would like to fertilize some small blueberry plants I bought this year. I have your BLACK GOLD RHODODENDRON, AZALEA & EVERGREEN FERTILIZER, and I have some questions about its use because I don’t understand the instructions. It says “new plantings, 500ml per 1.5 m squared.  Or 1.5 cups for every inch of diameter of the trunk.  My plants are nowhere near 1-inch in diameter.  I have a round pot, 15 inches diameter, and I have another plant, in a 14 X 20” rectangle. Also, doesn’t the depth matter as well when determining how much fertilizer to put in? Here are three more questions.

  1. How do I know how much fertilizer to put in?
  2. It says  “measure 6 inches above the soil line”. What is the soil line? Then you say “the drip line”. What is the drip line?
  3. The instructions say to mix the fertilizer in with the soil.  How do you do that once the plant is already potted?”

Question from JM of Toronto, Canada

Answer: We are happy to answer your question about how to apply Black Gold Rhododendron, Azalea & Evergreen Fertilizer. Here are the answers to your three primary questions.

  1. You will need to extrapolate from the guide suggestion: “Add 1.5 cups for every inch of diameter of the trunk.” For example, if the stem of your blueberry is approximately 1/2 inch in diameter, then work in 3/4 cup (175 mL) of fertilizer around the root zone of your blueberry. If it is smaller, extrapolate to add less.
  2. The soil line is the soil layer that covers the roots, while the drip line is the diameter area of the plant crown. Please see the schematic below.
  3. If you are adding fertilizer to a pot, then gently work it into the soil around the roots from the top. You do not need to work it in deeply. The fertilizer will make its way down to feed your plants every time you water.

We hope that this information helps.

Happy gardening,

Jessie Keith



Plants are the lens Jessie views the world through because they’re all-sustaining. (“They feed, clothe, house and heal us. They produce the air we breathe and even make us smell pretty.”) She’s a garden writer and photographer with degrees in both horticulture and plant biology from Purdue and Michigan State Universities. Her degrees were bolstered by internships at Longwood Gardens and the American Horticultural Society. She has since worked for many horticultural institutions and companies and now manages communications for Sun Gro Horticulture, the parent company of Black Gold. Her joy is sharing all things green and lovely with her two daughters.

Leave a Reply

Content Disclaimer:

This site may contain content (including images and articles) as well as advice, opinions and statements presented by third parties. Sun Gro does not review these materials for accuracy or reliability and does not endorse the advice, opinions, or statements that may be contained in them. Sun Gro also does not review the materials to determine if they infringe the copyright or other rights of others. These materials are available only for informational purposes and are presented “as is” without warranty of any kind, express or implied, including without limitation warranties of merchantability, fitness for a particular purpose, and non-infringement. Reliance upon any such opinion, advice, statement or other information is at your own risk. In no event shall Sun Gro Horticulture Distribution, Inc. or any of its affiliates be liable to you for any inaccuracy, error, omission, fact, infringement and the like, resulting from your use of these materials, regardless of cause, or for any damages resulting there from.