Question
Four or five years ago I bought a small orange tree with specific fertilizer instructions.  It isn't supposed to grow very tall, and it's supposed to have oranges in its third year.  All that it has are big thorns.  Someone told me that the thorns are the problem.  Should I prune?  Should I change the fertilizer?  It gets plenty of light and I don't water it very often.  It looks fine except that it has no oranges!

Answer
Hi Amanda,

It is easy to get distracted by the lesser elements and lose sight of the more important factors. Orange trees need direct sun all day long. That is hard to accomplish indoors and the most common reason that citrus trees do not produce fruit indoors. I don't know what you mean by "plenty of light," but your tree should be immediately in front of a south facing window that is uncovered and unobstructed. Light is the most important consideration.

Next most important is to keep your tree tightly potted. Flowering and fruiting plants rarely produce flowers and fruit unless they are quite potbound. So repotting can discourage fruit on your tree. I don't know your repotting history so I don't know if that is applicable.

Proper watering is also important. If yours is properly potted and moderately potbound, then you should water it thoroughly as soon as the top half-inch of soil is dry.

Local water quality may be an issue. If your tap water is on the hard or alkaline side, then switch to filtered or distilled. If the pH of the soil is allowed to rise above 6.5, then the fertilizer will not be available to the roots

After that, fertilize as directed but at half the recommended strength. Fertilizer doesn't really make much difference so don't get too focused on that. Likewise, removing thorns is not a factor. Pruning is more about appearances than about promoting fruit. Pruning will keep the tree more compact, if that is your goal.

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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