It's a lot less vigorous growing than it's parent yuzu. I had a small plant inside a greenhouse, and we had an extremely mild Winter, and the leaves still got trashed. I mean they looked really bad, even though most of them did not fall off. That's not necessarily an indication of its cold hardiness though. I noticed some cold hardy citrus varieties are quick to drop leaves at the slightest bit of cold, and it's probably a protection strategy, to go into dormancy to avoid possible damage if temperatures get colder later.