I planted 4 taxis baccata fastigiata trees 3 years ago. One is twice as wide the others.what to do? I was advised to take the corns off but it hasn't made any difference.
Most likely you have a genetic variation occurring in the 4 plants. Not much to do at this point. Pruning may help but the one larger plant will continue to grow wider probably forever. Have you talked to the nursery where you purchased the plants? They should replace it with one that is true to the expected form.