Inspiring!!
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Semi-tropicals like citrus and avocados aren’t frozen out by the average low temperature as indicated by Zone, but the absolute lowest temperature. For example Houston which is zone 9a had a low of 10F(8a) in February 2020. That low killed all unprotected citrus, rootstock and all. Since the last low of 10F in 1989 thousands of citrus trees had been planted around town and became very common. Not so common now!
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Some of those areas on Vancouver Island have impressively mild absolute minimums, though there isn’t great weather station coverage. For example, in the late December freeze when @JaneSquier was 7°F and my yard in Seattle was 16°F, the Tofino airport bottomed out around 19°F, and was above freezing during the day every day of the weeklong freeze.
Vancouver limitation for citrus would be low summer heat. Summers are very mild with most highs in mid 70s. Grapefruit wouldn’t do but meyer lemon might.
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Here are some photos of the trees after a virtually unprotected cold winter and cold wet spring. They are sprouted from fruit I grew in the greenhouse here in British Columbia.
Two trees died back to ground level, and both making spectacular comebacks, the bucket is for perspective:
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This one had buds survive and sprout at 5 inches above ground level. It’s having a tough time as the bark was damaged and now the new growth too. It seems an advantage to die back all the way!
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Here’s a tree I planted in April 2022. It is the same age as the previous two trees.
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And a photo I just took of the Holiday fruit set - July 2022.
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Looking great! What size is that tree, and what size is the greenhouse? And did you hand pollinate in any way?
My greenhouse multi-graft trees took off with growth this year, but I’ve had to do lots of pruning to try to keep them balanced among all the varieties on each tree. Even with aggressive pruning, though, they have added 4+ ft of new growth this year. Hoping for decent fruit set next year.
The greenhouse is 6,000 square feet. I also have 35 varieties of citrus in there as well as some other hardy-ish sub-tropicals. I prune to 8.5 feet which, is just below the gutter, so I can put up an energy curtain in the winter.
I don’t hand pollinate anymore, it never seemed to make a difference. The vents are open for pollinators and if there seem to be no pollinators around at bloom time I buy bumblebees from Kopperts.
If they set fruit they don’t grow much, if they don’t, they put on so much new growth!
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7F! That sounds like the temperature at the summit of Mt. Maxwell!! Victoria saw temperatures ranging from 15-25F during that week. I kept a Wurtz outside covered in remay and xmas lights. It died back considerably, grew back and then I killed it with too much nitrogen 
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Very jealous of that… that’s the size of my entire lot, house included! My greenhouse is just over 300 sq ft, which will hopefully be enough to have a few fruiting avocado trees to provide seeds for the outdoor trials.
This year I had flowers on Duke, Royal-Wright, and Aravaipa, but they were way too early for the bees to be out and about (January/February) and I didn’t hand pollinate since I figured the trees needed to get bigger anyhow. Next year I’ll hand pollinate or at least shake the trees to release pollen. Based on the amount of growth this year, I’m hoping for at least a chance of fruit on those three varieties, plus maybe Brazos Belle, Linh, Joey, and Jade. The other dozen varieties I’ve collected are smaller grafts and will definitely need another year before a chance of fruit.
Hi JaneSquire, thanks for posting.
One of my friends (who lives in Burnaby, BC) has a cold-hard avocado tree that he planted in his backyard by accident, 4 years ago.
This past winter (late Dec 2021) it got down to -14 degrees Celsius. (that’s 6.8 degrees F). His little Avocado tree is still alive!
He told me that 4 years ago, during its first winter, the little avocado tree barely survived (it only reached - 7 degrees Celsius that year). The next two winters both reached a minimum of - 8 degrees Celsius, and the tree wasn’t even fazed by the cold.
This year, in May, after winter ended, all the leaves fell off. But a month or so later, they came back out again!
My friend gave me this photo of the tree.
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Welcome to the forum, George! That’s a pretty impressive claim. Was that without any protection at all? I’d love to see what the base of the tree looks like, since my plants that survived even much milder temperatures are all regrowing from near ground level or even below, so you can see the dead stalk next to the new growth, like this:
Out of ~30 outside, it seems like I’ve got about 13 survivors, with only 8-9 of those growing vigorously. None of them had their stems survive more than a few inches above ground level. The Hass seedlings died entirely, the Mexican-race seedlings survived at around 50% rate. Only 1 out of 3 Lula (West Indies avocado) seedling rootstocks survived, and those were all about 4 years old. The survivor lost its graft, though.
Would love to get my hands on some Duke scions sometime. Have you read this blog regarding Avocado bloom time in colder climates?
It’s got me convinced that the Reed and Carmen Hass will be the best for our climate for fruit production. However these trees would certainly need frost protection as we do for citrus.
I’m not sure those would make it up this way (even with significant protection), but I look forward to updates on your attempts! I have seen that post and also a couple of good ones from the Western Australia ministry of agriculture, which have more detail on changes in flowering in cold climates. My takeaway was to disregard the A/B dichotomy entirely and instead focus on the cold hardiness of each cultivar. I’m also only growing var. drymifolia cultivars, or at least hybrids that show drymifolia traits, so that eliminates most of the commercially available trees. I’m not even going to attempt anything like Reed or Carmen Hass unless I have such unexpected success with the drymifolia trees that it seems worthwhile.
I’m not set up for phytosanitary certification, so can’t send to Canada (assuming that’s where you are), but feel free to reach out if you’re ever going to be in the Seattle area and want to pick up some scions in person.
Hi Jane. I’m new to avocado growing in BC but was inspired by videos of your growing on Saltspring. I’ve built a geothermal greenhouse and am looking to grow an avocado tree, but am limited with space (8-10’ tall). Do you know of a dwarf variety supplier that would ship to BC?
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You don’t need a dwarf variety, you just need to prune aggressively. Avocados like to get bushy if you cut them back, so once your tree is starting to get a little tall, cut it back in early summer so you get good regrowth later in the summer. That bushy new growth will go dormant in fall and should produce fruiting buds the next spring.
And welcome to the forum, @climber!
Edit:
I went down a bit of a rabbit hole trying to find good guidance on aggressive pruning for avocados, and this excerpt from a 2020 UC-ANR report on high-density avocado groves has some pretty good advice, which is to prune aggressively once per year:
Their “after harvest” advice is for Hass, so it won’t be as applicable for Mexican types, which will usually ripen in fall/winter. I think pruning after fruit set is clear in early summer is better in this case, but I might be wrong.
Here’s the full report, which is otherwise pretty inapplicable to greenhouse growing:
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