P. reflexa in Herbede, Witten, North Rhine-Westphalia, Germany

Karlheinz, i commented upon

This newly added Pinus ayacahuite might serve as another donator of pollen to achieve sound fertile seeds of hybrid origin, in addition to P. × holfordiana from Rodenkirchen, Köln, and P. wallichiana. I do not suppose you will try to manage pollination experiments on your own, as this needs a lot of time and some preparation. Maybe we can find someone to try pollinating studies with this pine, would be most interesting to study!

Unfortunately my estimation was right, had this experience with well formed but empty pine seeds several times.

Well, intentional pollination using pollen of same, or closely related species should work well for usual (right time and fresh, fertile male cones). Thus i wouldn't try to use P. armandii as male part, but rather some example of P. flexilis - strobiformis alignement, there could be some at Forstbotanischer Garten in Rodenkirchen, Köln.

For sure, collecting male cones and climbing up the pine for fertilization of female ones will be way too much of effort, something for crazy enthusiasts and experienced tree breeders!

Danke!

For testing viability, with a little experience, it is easy to tell between an empty and a filled seed just by shaking it in your hand - if it feels heavy, it is filled, if it feels lightweight, it's empty.

With many species there is also a colour difference, with filled seeds darker than empties, but this isn't obvious in the white pines. Works well for most hard pines and spruces though, and particularly obvious with pinyon pines (filled seeds dark yellow-brown, empties whitish).

I have changed from P. strobiformis to P. reflexa. Kiefernspezi replied to me, that he never had seen the two species at the natural location in Arizona and Jalisco in direct comparison. Before he would not like to commit himself. P. reflexa would explain the astonishing winter hardness.

Thanks to Conifers for support and literature research!

I have put all of them in the water, all swim well, no wants to go down. After that I cracked a few of them, there is no real core in it, they are virtually empty :-(

@Karlheinz the most simple fertility test: put seeds into water, swimming ones are +- empty and sterile, immediately sinking ones are full with good chances of viable embryos inside, so i would put these into soil and outside to provide so called stratification.

As said before, i do guess the main part will prove to be empty?, we will see :^)