The leaves on my three-year-old blueberry bush are yellowing and this year it produced hardly any fruit. It is in a pot filled with ericaceous compost, watered only with rainwater, fed with comfrey liquid, top-dressed twice a year, and given some slow-release fertiliser. What can I do?
Yellowing leaves suggest your blueberry is suffering from chlorosis. In these plants, this is commonly because of nutrient deficiency; it sounds as if your blueberry is lacking in iron. This tends to happen because the soil pH is too high, at which point the blueberry can no longer take up iron available in the soil. Plants need iron to form chlorophyll, which is used in photosynthesis. To remedy the problem, use iron chelate, either as a foliar feed or added to the soil. This is a short-term solution that works by reversing the deficiency in the soil.
Blueberries need a soil pH of 5.5 or lower to thrive. It seems strange that your soil is not acidic enough with all you’ve been doing, but it may have got out of kilter. You could buy a soil pH meter to find out what is happening. If the soil is not acidic enough, the quickest solution is to use sulphur chips to lower the pH.
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