Answer: These trees (Castanea mollissima) are not self fruitful, so you need to grow two varieties for pollination. Perhaps the third tree is not compatible with the other two in terms of bloom time and is not fruiting as a result. It is also possible, if it is a seedling grown tree, that this particular individual is just very shy to bear. If nut production is very important to you, you would want to select one of the varieties identified as being a good nut producer. Typically even seed grown trees will bear after about five years, so it should be producing nuts by now regardless.
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