I have two filberts that I planted 18 months ago. The pruning instructions I've found on line say nothing about when to prune or if timing even matters. I have suckers growing up from the roots all around both of them. Plus I'd be inclined to make them bushes as I believe is done in Europe rather than trees. Looking for info and/or relevant links. Thanks, Bill Chenoweth Lebanon
Linn County Oregon
Hazelnut trees tend to grow rather tall, on average 40 plus feet. Bushing can be done but the tree will still want to grow tall.
Hazelnuts also sucker from the ground which means yearly cutting.
The current best method for pruning hazelnut trees is open center, like a peach tree.
Pruning is best done October to March.
The OSU EESC catalog has good information on growing hazelnuts. The Linn /county extension office should have a good general pruning handout.