It took me a while to get around to this forum, but it seems that there is a lot more active discussion about hardy citrus! I’m glad if my videos have been any help to understanding the Prague Chimera better.
I though this might be interesting for those who haven’t seen it:
These photos come from jim VH and Lauta_hibrid on the Tropical Fruit Forum. Two separate occasions where the Prague Chimera has rearranged into novel combinations. Possibly due to bud damage or some other mutation, but it seems clear the tissue layers have rearranged in a way that then influences fruit characteristics, whereas in the original chimera, mostly just the vascular system seems to be affected.
You can see in the first photo, the plant appears to have Citroncirus leaves, much like a typical Citrange or other 50% Trifoliate Orange hybrid. The flower does not appear like a hybrid or a trifoliate orange, but rather more distorted like Prague flowers often are. In the second and third photos, you can see a darker branch with thicker thorns and trifoliate leaves (which appear longer than usual) which set a pubescent fruit with a short stem, very similar to the Trifoliate Orange. However, the exterior color and sheen are a little different from the Trifoliate Orange, and the interior color is a deep orange like a Satsuma. The vesicles appear intermediate between the two, and the taste was reportedly more like a hybrid Citrandarin or Citsuma (likely due to resin from the segment walls, etc).
I have personally seen Prague revert to both pure Poncirus, and pure Satsuma on 3 occasions, but it is a very stable chimera otherwise. I’m eager to learn more about Jim’s plant, as it may help us understand the full range of possibilities with citrus chimeras based on which layers (L1, L2, L2) are swapped. Also, it will be interesting to see if all of them exert the same or differing influences on cold hardiness. This would help our understanding of how the cold hardiness is imparted onto the pure citrus half of the chimera, which is useful for recreating one.
I’ve personally talked with the owner of Sweet Home Alabama Homestead, and based on our conversation, I believe his trees are so fruitful because of his diligent protection with Christmas lights and frost blankets. We don’t have a large enough sample size to really confirm this effect, but I can replicate it a few years from now with our own trees once they are more mature. I have over a dozen in-ground, maybe close to 16 including the ones on interstocks. I can protect half of them and see if there is a meaningful difference in production the following year. All trees seem to bloom well and set fruitlets but most are dropped regardless of hand pollination or any other attempts to maximize fruit holding.