I asked my daughter who works in a tree nursery in zone 3a. She said that variety is a dwarf dogwood and gets 4 feet tall by 4 feet wide when mature.

Thank you, don! Hmm.... maybe I should get the regular one that is not a dwarf, since I want this to be closer to 6 feet tall? However, I heard that the other one (Elegantissma???) is a bit wild and big....

Does anyone have any experience with the Variegated Siberian dogwood?