I've got a blueberry in a pot that was repotted without amending the soil. Now it seems to be growing okay but rather then repotting it again, I'm wondering if I can apply a coffee grounds mulch while it still has a few berries, and i mean only a very few berries compared with the numbers on it when i bought it just on a year ago. Or should I wait?

I haven't tested the soil pH, and I don't use tap water for watering, but fish water from my gold fish. I did put some citrus fertiliser on it once late last year, and we're now in mid summer.

2 Answers 2


Amendments for blueberries in the fall. Goldfish pond water is probably good because the organic material in the water lowers the ph some. However blueberries like acidic soil. They grow under the canopies of great trees in the wild which keeps the soil pretty acidic.

Blueberries also like lots of water. You want a very loose humus that will dump all the water and not stay wet, but you need to water often.

  • My main concern after further reading was whether adding nitrogen mulch would cause the fruit to prematurely fall as happens in some other plants. Fall sounds good. Yes, I use gold fish bath water rather then tap water as the pH should be a little on the acidic side. Jan 18, 2016 at 1:28
  • Fish water is sometimes to concentrated with ammonia.
    – imrok
    Jan 21, 2016 at 6:36
  • If the fish are alive there isn't too much ammonia
    – Escoce
    Jan 21, 2016 at 13:19

Test the pH. Blueberries do best with a pH between 4.5 and 5.5.

Blueberries are bog plants. They like a soil with lots of organic matter.

They are not heavy feeders. More than just a trace of nitrogen will result is lots of lush green leaves, but not many berries.

Blueberries are nominally self fertile, but will bear far more heavily if you have a different cultivar in the neighborhood.

  • Phosphor and potassium should help fruit developpment, where nitrogen will only favor the growth, as you said about leaves.
    – imrok
    Jan 21, 2016 at 6:39

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