I see some nurseries use D. Lotus for rootstock.
I was curious myself what rootstock my Saiju is on. Bought from Raintree which is west coast nursery 10+ years ago. Never sends root suckers. Does fine in East Coast Philly for me.
So if yours sends up suckers , maybe its more likely D. Virginiana
I should add that I keep my scions wrapped in a thin wrap of parafilm (or other) that is thin enough for the buds to push through. I let the buds push through. Keeping them wrapped has been important for me. If I remove the wrap (Iāve used things other than parafilm and sometimes the buds have a hard time poking through) for some reason, and then get hit by 100F, dry (15% humidity) and 30mph winds, the scion can get fried in just a day (been there and done that) even if the tree is well watered. Having an emerging bud (that has not yet poked through) wrapped by parafilm, and hit by very high temps does not cook the emerging growth. Itās generally similar for a scion well wrapped by parafilm with buds poking through. Occasionally issues can happen with any graft though.
I mostly wrapped in parafilm this year with no foil. I did wrap 3 in foil. I noticed no difference though even with grafts on the same tree, one with parafilm only and the other with parafilm covered then with foil. One was a little further ahead, one a bit behind, and one the same in terms of quickness to leaf out. Inconclusive results as to whether foil matter. Parafilm performed fine of course across grafts (~30 grafts total).