Does anyone have experience with growing Japanese maples seeds from popular cultivars?
Contrary to popular belief in North America and Europe, in Japan it is common practice to grow certain cultivars from seed. However, it's important to clearly label them as such, because a seed will 'never' retain 100% of the genetics of the parent plant material. This is especially common for Arakawa in particular, but I have seen it done for Deshojo as well. Technically, it would suffice to refer the cultivar as 'arakawa' (using single quotation marks) and to the seedlings with rough bark as arakawa (the adjective and noun, meaning rough skin i.e. bark). But that system is prone to error, so it's much better to simply refer to the seedlings in long form as 'seedlings from an awaraka'.
As a general rule, it's good practice and strongly recommended that we use cutting, grafting, and air layers to 'preserve' cultivars*. Yet, as important as that idea is, it's often overstated. We tend to overlook the fact that epigenetic factors (notably, but not exclusively, environment) can alter gene expression and therefore phenotype (i.e. observed differences) without altering the underlying DNA sequence. I mention this because I have seen seedlings of deshojo, arakawa, and beni chidori that
appear in a given plant at a given moment more like the cultivar and parent than a cutting from that parent plant might.
*I would add that there can be significant phenotypic difference when a cultivar is on its own roots vs grafted (and, by and large, the nursery industry around the globe has named cultivars based on grafted specimen).
So you’re telling me there’s a chance I can win the lottery? What are the chances that a seedling can have rough bark and small red leaves with tight internode?
I personally grow 'Yves Arakawa', which was grown from a seed and develops rough bark like 'Arakawa' with other advantages (like vigour and apex strength). Mr. Valavanis has also been collecting seed from his 'Arakawa' for many years - he has written about it on his blog and here too I believe. In other words, there is precedent that your seedlings
will could develop nice consistent bark. As for leaf shape/size/color, it's hard to say. Sergio (M5Bonsai) gets incredible spring color on his 'Arakawa' and from memory that seems to be a consistent trait, which I have not seen any other 'Arakawa' or arakawa get quite like it