Commercial scale citrus in the cold?

[Peasefamilyfarms]

Random question, I was listening to a podcast the other day and they were taking about potential commercial scale yuzu groves being planted in Oregon. And that got me to thinking, is there any commercial scale citrus being grown in any non traditional usda zones?

[caladri]

USDA zones are misleading, and I suspect not what you're really asking about. The Pacific Northwest is challenging in terms of heat units more than in terms of annual low, although prolonged cold periods can be problematic. Walter Raleigh grew groves of sour oranges in Surrey, England, which were quite long-lived before being wiped out by a single bad year. There is a bit of commercial citrus in cooler parts of Japan and China (possibly also Korea?), and there are piles of (mostly failed or poorly-performing) Soviet efforts across some parts of the USSR that are certainly not traditional citrus-growing regions.

It would be interesting to know what rootstock those plantings are using, as my own experience talking to commercial growers who are considering growing yuzu up here in BC is that they have absolutely horrible ideas about rootstock selection.

[drymifolia]

It would be interesting to know what rootstock those plantings are using, as my own experience talking to commercial growers who are considering growing yuzu up here in BC is that they have absolutely horrible ideas about rootstock selection.

Is there any reason not to just use yuzu seedlings as rootstocks for yuzu? Most yuzu selections are so seedy that they would at least be an easy rootstock to come by for anyone with a fruiting yuzu nearby. I have one (strongly suspected*) yuzu seedling that went in the ground recently here in Seattle that I'm not even intending to graft, and it's been very vigorous. It did spend last winter in my somewhat heated greenhouse, but was basically the only citrus in there that stayed deep green all winter.

* We did a weird citrus tasting thing with some friends and all the seeds got mixed up, but both statistically (# of seeds) and in terms of phenotype, yuzu is my presumption.  I can't recall what % of nucellar seedlings they make, but mine looks very similar to the rooted yuzu clones in terms of leaf shape and such, so it's either nucellar or yuzu x yuzu I'd guess.