A yuzu tree grown from seed has proven to be reliably hardy for me unprotected on a roof terrace in an urban setting. I have found that the decisive factors for me for winter hardiness are next to the genetic predisposition of the plant the size of the stem and the pot size. The pot has to deep enough to minimize the perched water table and prevent it from completely freezing through when the Arctic temperatures hit. Aside from its hardiness, yuzu is attractive to me for be very fast growing when given the right conditions, namely warm days and nights and plenty of moisture and fertilizer. My loft apartment provides plenty of heat in the summer and I was able to get a meter and a half of growth on a tree in one summer. That was impressive. These factors make me consider using it as a rootstock for getting plants up to size before I try to overwinter them on the balcony. I recall reading that the Japanese used yuzu for a time as a rootstock for satsumas and it pops up as a rootstock every now and then in scientific papers but perhaps someone on this forum has experience with it as a rootstock already and can report of their findings. I presume it would be a good match for plants which are considered to be related to yuzu, like sudachi or kabosu. I plant to graft my yuzu on it this season if the seedlings that I germinated last month grow fast enough.
