I am trying to propagate my own rootstock using the stool bed method where you just plant a whip horizontal, roots in dirt, stem in wood shavings and last year it worked pretty well with some Apple rootstock.
I have purchased some Pyrus Ussuriensis rootstock from Burnt Ridge and I want to know if I can do this with this rootstock, or if it is normally propagated through seed. Am I taking a risk of cloning a random seedling Pyrus Ussuriensis that might suck when I graft a bunch of them over to Euro and Asian pear? Thanks Much!
A perennial cultivar, by definition, is propagated asexually.
This should save you money and time FRUIT TREE SEEDLINGS | Willamette Nurseries rootstock clonal seedling fruit tree ornamental seedlings .if your in zone 4 i believe Pyrus betulaefolia will work for you. The problem is harbin aka Pyrus Ussuriensis die from pear decline. I do grow them both and it does happen. Pyrus communis should be fine in zone 4 also and might stay smaller but still large. Neither are as large as harbin. They will run out of rootstocks soon i think so if you want bulk its good to order early. If you want to buy ohxf rootstock in bulk try https://www.copenhavenfarms.com/
On your original question both BET and Bartlett are commonly propagated by seeds for rootstocks. Williamette sells both of those. I expect Bartlett may not be hardy enough for you but BET is. I have grown pears on both of these and they work fine. But the clones are overall a bit better.
To make your own either get one of the OHxF clones and propagate by stooling, or find some BET seeds (which could be hard to find). Clark has experience with Ussuriensis which sounds like you want to skip on that one. I never tried it myself.
Yes a zone or 2 colder it is a great rootstock when its to cold for other rootstocks. The decline is associated with psylla. “Select a cultivated pear tree that uses a rootstock from domestic Pyrus communis eg ohxf. Its chances of catching the pear decline phytoplasma are much less than for trees with Asian rootstocks like P. ussuriensis, P. serotina or P. pyricola.” https://www.gardeningknowhow.com/edible/fruits/pear/pear-decline-phytoplasm.htm .Out of the 25 harbin planted 3 trees remain alive. No other rootstock was lost to psylla related illness.