growing grapefruit

Question

I have a grapefruit that bears prolifically but the fruit does not mature

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Answer 1

This can take nine months or longer sometimes. If it is well passed that, and still not ripening, then I would suspect that there is, either, too much nitrogen in the soil, or not enough phosphorus and potassium.

If this is not the case, then I would chalk it up to a pH imbalance in the soil. You can mitigate this by adding dolomitic lime, and iron sulfate to the soil along with your regular fertilizer in the spring.