Hello, UBC Botanical Garden members, I purchased some coastal Douglas-fir seeds from Vancouver island in an attempt to grow some here in Oshawa, Ontario. As a backup, I also have some locally gathered Douglas-fir seeds. This January was quite cold, getting down to, albeit only for an hour or two on a single night, -26C, or -15F. More commonly, our cold nights go down to temps just on the border of USDA Zone 6a and 5b, -21 to -24C or about -10F. My first question is: what subspecies (coastal or inland) is my local collection tree (images link here: What Douglas-Fir Subspecies?)? Despite the answers I received on Reddit, I am quite confident that it's an inland, hence why I purchased seeds from Vancouver island. Secondly: if my coastal seeds manage to germinate this spring, what should I expect for cold tolerance from this variety? I have seem mixed information. Some sites claim a USDA Zone 5 cold hardiness (-10 to -20F), although this could be regarding the Cascades as opposed to the Vancouver Island variety. I've also seen Zone 6, which would be dangerous for me (-15F) and, even worse, Zone 7. If the Cascades can do those temps, might I get genetic exceptions from the Vancouver Island batch that could do those temps also? I realize that heat may also pose a problem, but I thought I'd get the cold question out of the way first. I can always attempt to Bonsai myself a Lynn Valley Tree! Thanks!
I was fully expecting this (the existing tree) to be Interior Douglas-fir, but the photos look far more like Coastal, both in the branching structure and the cones. Coastal Douglas-fir will take temperatures down to -28°C to -30°C or possibly a little lower, so your current winter should not harm it. What's important here, is the difference between average winter cold (as quoted in the USDA Zone ratings) and extreme winter cold (the coldest winter that happens in the tree's natural lifespan of several centuries). To survive for the long term, a tree has to cope with the extreme, as well as the average. So its actual cold tolerance is well below the USDA Zone figure for its origin. A zone 7 winter (typical of Coastal Douglas-fir's native range) has an average minimum of around -15°C, but in an exceptionally severe winter, can reach down to around -27°C to -30°C. Likewise, your average Ontario zone 5 winter gets down to -25°C or a bit below (which won't hurt a Coastal Douglas-fir) BUT . . . an exceptional severe winter there would get down to probably -35°C to -40°C. Which will kill a Coastal Douglas-fir. So far, you've been lucky, and in the young tree's short life to date (my estimate from your photo: 16-18 years), that hasn't happened . . . yet. Whether it ever will now with global warming, is an unknown, but quite possibly not. I fear heat is more likely to pose a problem, particularly with warming. Douglas-firs are in particular not well adapted to the combination of summer night-time heat and humidity that characterises the eastern North American climate; in the west, summer heat generally has low humidity, so the nights cool off better, which gives the tree respite. Heat + humidity combined however, makes Douglas-firs very prone to fungal diseases (leaf blights) in particular. So you'll need to check out for those. PS - welcome to the forums!
Hello, Michael. First off, your answer is fantastic! Thanks! I know, right! Being highly curious on the matter of distinguishing coastal from interior, what about the branching and cones resemble the former variety, especially with regards to branching structure? I'm aware of the difference between coastal and interior bracts, that being that the coastal is not reflexed, but seeing slight refection on the lower bracts of the existing tree's cones, what "amount of reflexion" is normal for coastal trees? Does this apply to a seed from a Vancouver Island collection site the same as a Cascades and Sierras (see table of temperature: Pseudotsuga menziesii subsp. menziesii (coast Douglas-fir) description)? I've heard of variation within the coastal species, and know that Vancouver Island is warmer. But I've also heard of "cold spots" on the island, near Comox glacier, for example. Damn, I thought global warming might help with the extreme winters you mentioned. If global warming keeps us at -30c, the summer heat will be worse. The tree's between a rock and a hard place! To give it the best shot, where do you recommend I plant it to reduce blight (in an open field, the creek, a park, etc.) ? The existing tree is an an open field facing west, which is the most common wind direction. Also, should I be giving it anti-fungal treatment? Again, thanks!
Hello, Sulev. Do you know whether that Douglas-fir in Estonia is of the coastal or interior subspecies?
Best options for minimizing leaf blight diseases is to maximise ventilation, and well-drained soil, so there is less humidity held in the air..
