I wasn't aware that planting one seed with another causes gene splicing? I'd research that if I were you
. It's more likely that one seed would out compete the other thus suppressing it's growth. I'm not a botanist though so I could be wrong.
You can get hybridisation between some trees, but this is usually between trees in the same genus rather than family. So if there are other cherry trees in the area it's possible (although I haven't read of this in any id keys for cherries) that through cross pollination there might be hybrid seedlings/saplings. If you didn't know by the way the latin name for J-cherry tree is
Prunus serrulata although I think there might be others.
You also have to remember that it is a combination of genes (genotype) and environmental factors that affect physical appearance (phenotype). Depriving (or heavily loading) an organism of certain nutrients can result in a very different appearance from the norm e.g. a lack of vitamin D in humans causes rickets resulting in legs that are bowed.
It's unlikely that the trees have majorly evolved (if at all) or mutated (unless they've been subject to heavy metals,abnormal radiation or a very nasty pathogen).
You might want to check out these guys too:
Reconsideration of the Prunus serrulata complex (Rosaceae) and related taxa in eastern Asia
Authors: CHANG, KAE-SUN1; CHANG, CHIN-SUNG1; PARK, TAE YOON2; ROH, MARK S.3
Source: Botanical Journal of the Linnean Society, Volume 154, Number 1, May 2007 , pp. 35-54(20)
Publisher: Blackwell Publishing
Science-bit over.
