Hi, I'm new to this climate zone stuff, and I'm trying to figure out how all the gardening books come up with these zone classifications for each plant. Can you suggest where I can find some information about a plant's climate zone classification, that would include references (as to how it got classified this way in the first place)? Is any of this based on scientific journal articles or is it more just word of mouth spread of information? Thanks!!
Thanks! Yeah that is a good summary. The question I was trying to ask though, and I probably wasn't too clear about, was not how the zones themselves were created, but the hardiness information about each individual plant species. In particular, I'm researching the monkey puzzle tree, and I read everywhere that it is hardy to zone 7, but I haven't found any references for this information. It just seems to appear magically in every gardening book. So I was wondering if anyone can give me some insight into how this zone 7 hardiness rating was established for the monkey puzzle tree? Thanks so much, sorry to keep bugging you guys!!
- Trial and error by gardeners and nurserypeople - Observation of native distribution range of plants, and assuming that plants growing in (or limited to) similar areas have equivalent zones - Research and field trials in an academic environment Hard to say without digging what method was used for a particular species. Also, what is published is not always correct.
Books and other sources typically give a range for each plant, there is no clearing house where an official hardiness is established using scientific methods.
Hardiness for commercial crops, such as fruit trees, is much better researched; often for ornamental plants there is much variability between what literature cites and actual garden experience. And many hardiness ratings do not take into account summer temperatures or unseasonable temperature swings. Many new plants to the trade have very conservative hardiness ratings based on where the wild populations grow. I know of one mail order source that no longer lists hardiness ratings for the ornamental plants they sell, as so many have survived in zones much colder than the literature cites. Use the ratings listed as a guideline only. Having said that, this current cold spell may show how much zonal denial I've been in the last 10-15 years....
Two nights below 20F (around Seattle) shouldn't be that big of a deal. Anything taken out by that really isn't hardy here at all. Early rhododendrons and others with tender flowers have already been turned to mush by previous nights in 20s, an additional set will probably be added by next two nights. But most such plants will lose flowers, maybe in some cases a little new growth only. In 1990 it was 5F (or lower) here.
