Why are my hazelnuts only the size of a pea after growing for over five years?
My hazelnuts are only the size of a pea. I’m not sure what the variety is but I got the seedlings 5-6 years ago.
There are several reasons why your hazelnut harvest is small (meaning small individually, not volume harvested). Hazelnuts do take several years to establish before producing a good harvest–I think you should be inside the productive window after 5-6 years, but it is possible that your seedlings are lagging a bit behind in development, especially if they receive shade or insufficient irrigation. Obviously, irrigation should be a problem this year (!), but if the trees were dry the last couple of seasons, they may still be moving toward full maturity. Along the same lines, the unusually wet weather has caused all manner of out of the ordinary issues this year across Maine gardens, and hazelnuts do not like perpetually wet soil, so drainage could also be a factor if your seedlings are in a low area. Hazelnuts in excessively fertilized areas can also prioritize leaf growth over fruit production, so it might be worth getting your soil tested through the UMaine Cooperative Extension Soil Lab–you can note that you are growing hazelnuts and the lab can cross reference results with recommendations for that crop.
As long as the trees appear healthy and your harvest is tasty, I would encourage you to keep doing what you’re doing and see where things go. I will also include a few general resources on growing hazelnuts that you might find interesting: