elderberry growing in zone 3

elderberry growing in zone 3. this was my second winter with them, and even with a good snow cover all of the top growth wasn't alive in the spring, but maybe it's fine they easily regen from the roots. now that I know, will just plan to crop them all for cuttings in the fall, which is totally fine for me. I'm also going to take softwood, so these poor bushes might not get very tall. anyone else growing elderberry where it's -40 in the winter?