Answer: There's no documentation to support the statement that lemon and apple trees are not compatible. Your zone 11 garden is borderline for citrus, so if the tree doesn't bear fruit, the most likely cause is winter cold, not close proximity to an apple tree. Before moving, or removing any of the trees, I'd observe them for a few years to see whether they're putting out new growth and attempting to develop flowers and fruit. Let their performance be your guide to renewing or renovating your orchard.
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