Hazelnut trees not bearing

I have 3 Turkish Hazel nuts and 2 American Filberts. The Filberts I bought a few years ago, and they bear consistently. The Turkish ones I planted 9 years ago from seed. One bore a few nuts last year, but the other 2 have never borne. I have attached a photo of one of the non-bearing trees. For scale,  it is about 12 feet tall.  Any thoughts on why they are not bearing, and advice to correct the problem?

My hazelnuts were planted some 30 years ago and have never produced actual nuts - proper sized empty shells, yes, but never any actual nuts.  There are 2 - as advised by the nurseryman, for pollination purposes.
It will be interesting to find out just why this is happening.  Could be lack of seasonal rainfall for me . . .

I'm not an expert but it seems Turkish Hazels are fussy about pollinators, only some varieties work for specific varieties, could be it. May be hard or impossible to determine if they are seedlings or don't know variety.

Can't  see anything saying American pollinates Turkish.

Maybe try to find a Turkish hazelnut expert, an orchardist perhaps

I have about 100 hazelnut bushes (probably what you call american hazelnuts) and they don't all produce.
I'd say less than 50% produce nuts, maybe around 10%.

Some sources say Amercan Hazel need different variety or species for pollinaton others say self fertile, perhaps it depends on the strain. I've planted mine with European hazel varieties that hopefully flower at same time for pollination, will be years before I know if it works.

David Nicholls wrote:Some sources say Amercan Hazel need different variety or species for pollinaton others say self fertile, perhaps it depends on the strain. I've planted mine with European hazel varieties that hopefully flower at same time for pollination, will be years before I know if it works.

That's the advice i've gotten as well and it seems to have worked across about two dozen trees here, a mix of nursery-sourced varieties and seed-grown volunteers that I transplanted. The only exception to this has been the two Barcelona trees, which seem to be all about producing wood and not nuts. They were far and away the biggest ones on the property, even though they're several years younger than the first ones i planted, and I don't think I have seen a single nut come from either of them. (I looked up the variety and technically they are a European cultivar that was used to start the Oregon filbert industry over a century ago, so there's that.)

So this winter they became the inaugural volunteers to the coppicing rotation. I'll see how the new growth fares...maybe the wakeup call will be good for them. One bright spot is that I gained a lot of perfect hardwood sticks for the RMH.

To clarify, it is the Turkish ones that are not bearing. I started them from sprouted nuts from a pair of trees that have been bearing consistently for many years. The originating trees do not have a pollinator of another variety.  Do they need to be pruned back? I have heard that hazel nuts  bear better when pruned rather severely. Can anyone confirm that from their own experience?

I know you were talking about Turkish. There seems to be no mention online about pollination of Corylus colurna (Turkish Hazel) seedlings, in English. hard to know if this means it generally doesn't work.

I have searched in Japanese on native plants there, cutting and pasting the Japanese words for those plants given by Google, then searching with them, then using Google translate to read the sites that came up, it produced a lot of useful info that did not come up in English searches.

I don't know if Turkish Hazel is big in Turkey, if it is this might work searching in Turkish, a long shot.    

PS " The nut can only be found on female trees. Nut production is irregular and occurs every two to three years [4]"-  Wikipedia

That may be it, your Turkish may all be male, that might also explain nuts on the supposedly self- sterile American, it may be the Turkish are pollinating it

I'll report back on the severe pruning question, but it will take at least 2-3 years because the first test subjects are stumps.