Hello everyone, and Happy New Year. I hope this finds you well. I'm hoping some of you can either share your knowledge or point me towards studies regarding this topic. I live in Wyoming, USDA zone 4b. We regularly see -30 F (-34.44 C). Most of my maple collection is grown in pots and kept in a cold garage for the winter, but I do have a Pseudosieboldianum as well as two Pseudosieboldianum x Palmatum culitvars; 'Ice Dragon' and 'North Wind' from Iseli growing in my landscape. (I'm not certain what Iseli uses for rootstock but I'm hoping to find that out.) My primary question centers around a number of Sieboldianum cultivars and upcoming Pseudosieboldianum X palmatum cultivars from Matt and Tim Nichols that I know are grafted to acer palmatum rootstock. I may just have to experiment by planting trees out, but I'd like to research as much as possible first. I've heard that grafting will cause rootstock to adopt characteristics from the scion plant, such as hardiness. This is also taught in the bonsai world, where say a Ponderosa pine can't be kept healthy in Southern California, but if you graft the foliage over with pinus thunbergii it can thrive. Does anyone here have knowledge in this area or know where I can access scientific studies regarding this scion to rootstock phenomenon? Thank you
Hi Dan, The pseudosieboldianum (hybrides) from Iseli are grafted on pseudosieboldianum. That's the only way to guarantee cold hardiness. I'm a little surprised to hear that Mr Maple is using palmatum rootstock, which sort of defeats the purpose. A. pseudosieboldianum rootstock is available in the US, and easy enough to produce. In EU, however, all of these selections are grafted onto palmatum, and the general understanding is they are not fully hardy. It's typically accepted that rootstock has a lot of influence on scion performance, in many ways, but the reverse is much less obvious though also well accepted, see https://academic.oup.com/jxb/article/70/3/747/5210403?login=false What seems clear is that modifications are less genetic, except in the immediate region of the graft (sorry, lost the reference for this and no time to find it), but more involve signaling pathways, see https://pmc.ncbi.nlm.nih.gov/articles/PMC7398338/ If anyone can point to a paper demonstrating genetic alteration of rootstock by the scion, I'd love to see it. I don't think rootstock hardiness would be among the set of parameters which the scion could modify, those being more restricted to aspects (as one might expect) like root mass and length. Further, I've had many JMs and others where less hardy palmatum rootstock died or was badly injured by low temperatures, where the Sec Palmata top was perfectly fine. HTH, -E