Hi, I'm in Olympia, WA and trying to grow hardy citrus outside. Most of them are rarer varieties. Olympia, WA has a similar climate to Seattle but the Winters get a tiny bit colder and the Summers get a bit hotter. Also night temperatures in Olympia often tend to be maybe 2 degrees lower than Seattle. This is the progress of how various varieties have done outside here: Yuzu, on dwarf rootstock, bush only 20 inches big, survived the first Winter (2017-2018) covered in a clear plastic bag weighed down by a gallon container of water. Some of the outer leaves looked scorched, but mostly was fine. It was a very mild Winter, there were camellia bushes that Winter blooming on new years day, and even a rose bush that still had a partially frozen but fresh bloom on it and was trying to bud out more blooms. The Yuzu began recovering very quickly in late May to early June. The second Winter (2018-2019) was more difficult. The plant was unprotected (except for one night when the temperatures dropped their lowest) and was completely buried in deep snow (which is not common here). The temperatures did not get that low though. On the coldest night I measured 24 degrees F ( -4.5 C) right outside the doorstep 3 and a half hours before it was forecasted to drop to the lowest point of that year. Keraji seedlings, growing on their own roots, both rather small, one of them maybe 4 inches high, the other 6 inches high. They were both covered with clear plastic containers, and ended up getting buried in snow. During the coldest night a gallon container of warm water was set next to them (3 and a half hours before the lowest temperature point during that night) and they were covered with a paper grocery bag on top of that. As of late March, the bigger one of them appears like it's not going to make it. The leaves are all dead and there's only a streak of green on the upper stem. As for the smaller seedling, most of it got killed back but the very bottom part of the stem is still green and there's still one very small green leaf down there close to the ground that's still alive and looking well. From my research, Keraji is supposedly able to survive 12-14F in the South (but maybe that's on trifoliate rootstock), and is closely related to Satsuma mandarin. (I've pieced together some DNA studies done in Japan and Keraji appears to be a triple backcross of Kunenbo to Shikuwasa, whereas Satsuma appears to have originated from a cross between Kishu and Kunenbo. Kunenbo 九年母 was the variety that preceded Satsuma in Japan 400 years ago, and is basically a large sized mandarin, very aromatic, that has some distant pomelo ancestry, it is also seedy, and probably the origin of Satsuma's cold hardiness) Dunstan citrumelo, on trifoliate rootstock, this variety is supposed to have better flavor than Swingle, almost like a more sour grapefruit or lemon. Seem to survive very well through the deep snow. The full extent of damage did not become fully evident until late March, the leaves look fried, but for the most part still retain some green color (new leaf growth will probably replace them). The stems are still all green and it will likely have no problem growing back. It was completely unprotected. It's branches actually got weighed down and bent over by the all the ice freezing onto the leaves, but even by the end of February when the snow had all melted the leaves still looked very green, more so than all the other varieties. Satsuma mandarin, on dwarf rootstock, about 3 feet high. Was covered by clear vinyl plastic. Some of the branches on one branch got fried, but the leaves on the top branch are still green, though a bit yellow in hue. The plastic cover got weighed down by the snow. There were 3 gallon containers of water under the cover that never froze even on the coldest night. The Satsuma doesn't look the best but it appears to have survived. Actually the Winter here was very mild until the early part of February when winds from the Northeast started blowing in down the Puget sound and large amounts (relative for this area) started falling. Probably in a typical year, a light snow might fall but it does not stick to the ground for long.