Hollow hazelnuts

  We were very exited last year when, after ten years, we finally got our first crop of hazlenuts. Unfourtunatley, after drying them, they were almost all hollow when we went to shell them. Brief research suggested the soil wasn't fertile enough, so over the winter I applied mulch and aged poultry manure. I was exited to see another decent crop this year. When I cracked them fresh they were all full nuts, but after drying all were hollow again. At this point I have very tall squirrel feeders, what can we do?

Empties puzzle me. When I think about the resources the tree needs to expend to grow a full-sized shell even though there's no developed embryo inside, the hypothesis I always jump to is the decoy. Any nut-bearing tree needs to fool some of the squirrels some of the time if it's going to reproduce. Or it has to crop so heavily that some of its nuts get buried but not dug back up.

We consistently get 10-20 percent empties on our hazelnuts every season. Lots of them are beauties...big and glossy, and you don't know it until cracking time. But I would say that the majority look a little suspect: dull, and with a husk that doesn't fall off. My assumption is that the good-looking ones are the decoys (they fool us, so why not) and the rest are just blanks, but still a "waste" of the trees' energy unless you think long-term in the sense that the nutrients will get back into the root zone.

I don't know what to make of your trees, though. When we get empties, they don't have filled-out kernels freshly picked. That does seem like a deficiency of some sort...mineral maybe? What is the pH of your soil? Can you get some rock dust and sprinkle that around?

This is a puzzling problem, I can offer no knowledge atthis point but hope to glean some in the future when someone else has an answer

I always assume that someone (animal) else has picked the good ones and left the bad ones. The mice (squirrels) and birds can tell better than us whether a nut has a kernel. If you pick them too early they haven't formed, if you pick them too late you get the (empty) rejects....

I noticed the same with my hazelnuts the first couple of years they started bearing nuts. Nuts were in the shells of most of the nuts I cracked and ate soon after harvest, but after leaving nuts picked at the same time for a month or two, just the teensiest shrivelled husk remained inside. But since those early years, the issue seems to have resolved and I now get far fewer empties.

I also wonder if there are just more empties some years, that maybe weather conditions meant there weren't enough pollinators active or the right sort of breezes to wind pollinate them or a lack of compatible pollinating tree also in flower at the same time, so though a nut forms, there's no embryo inside.