Toka plum ripening and own-root propagation

toka plum, the bubblegum plum. ripe in the first week of september, they have the coolest flavour it has a strong hint of bubblegum, quite unique. it's an old Hansen introduction from South Dakota, a cross between the american wild plum and the Chinese apricot plum (Prunus simonii). This plum has the ability to graft onto wild chokecherry rootstocks, and the softwood has a rooting potential. So the way I propagate them is from chokecherry glafts, then with early June softwood to create own rooted plum trees - and these are good because you can grow them as a vigorous bush, Toka does grow quickly, and if you were to cut it back or have some winter damage or maybe from wildlife, the growth from the root crown is still Toka, there is no graft union. Own rooted plum trees are likely to be long lived and healthy, and it's been cold hardy to zone 3 over the past four years growing them we've had plenty of -40 nights in Jan-Feb. I have a set of own rooted bushes that are about waist height that are getting planted out into our orchard this fall to compare them to the grafted ones.