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Is a "cool climate" one that doesn't freeze? Is it one that doesn't freeze until such-and-such a month? Or is it one where the temperature almost always stays above freezing?
Related to this, would "cool climate" plants have a resistance to occasional night-time frosts?
I ask because I'm wondering what chance cool climate vegetables would have in my backyard garden, where it can be consistently frosty starting anywhere from the end of November until mid-January.
"How long is a piece of string?" :-)
Here in North Texas we get frosts in winter but most people would not call it a cool climate - we had highs over 100F for most of 3 months this summer (yes August was the hottest average month for any US State ever recorded).
What you are thinking of as "cool" is probably what I usually describe as "temperate" - typically 40-60 degrees north - places like Washington State, Maine, the UK, France, etc. They get frosts but don't get hot. However "cool" is definitely a relative term: in Costa Rica we'd use the term for areas at altitude which are cooler than the Central Valley.
So it depends on your reference point, but yes I'd expect a cool climate plant to have a good frost tolerance - but if you were buying a plant labeled as "cool climate" in Hong Kong, or Central America (say), then it probably wouldn't...
I see you're in Newfoundland/Labrador: So I'd definitely call that a cool climate. I would expect your vegetable growing season is from spring through to autumn. Similar to what we'd get in the UK, although if your last frosts are in January you may be able to plant stuff earlier (eg. February).
Cool climate plants are plants that grow best during the cool, damp time of year starting near the last frost in spring, and sometimes in the wet period of fall. The plants that grow best during this time are naturally tolerant to some frost. Read the seed packet instructions for the information needed to properly grow these plants.
Vegetables are either:
Cool-season veggies grow best at temperatures averaging 15°F cooler than those needed by warm season types.
Warm-season veggies require both warm soil and high temperatures (with a little cooling at night) to grow steadily and produce crops.
Cool season plants thrive in cool temperatures (40°F to 70°F daytime temperatures) and are somewhat tolerant of light frosts...
Warm season plants thrive in warm temperatures (65°F to 90°F daytime temperatures) and are intolerant of cool temperatures...
Some vegetables can take Wintertime, cold (freezing) weather much better than others, in fact some only reach their full potential (flavour) if they go through a few "light" freezes or a complete Winter (can be over Wintered in the ground) eg
Knowing the answers to the below questions, plus others, will enable you to work out the correct times of year to plant (sow) and harvest...
Q. What vegetables are you considering growing?
Q. What Hardiness zone are you growing in?
Q. What are the average first and last frost dates for where you are?
From your SE profile I see you are located in "Newfoundland and Labrador, Canada", therefore you might find the below article from Newfoundland Botanical Garden of some interest:
The use of "cool climate" in the question and "winwaed" opening comment, "How long is a piece of string?" :-) had me wondering if there was a definitive definition of "cool climate" used in horticultural...
I couldn't find one online (that's not to say there isn't one).
I asked some "experts" on twitter, no one could point me to a definitive definition.
I'm currently left thinking "cool climate" isn't a good term to be used in horticulture, it's too open ended...
Below are a few responses I got on twitter when I asked, "Help, looking for a definitive definition of "cool climate" used in horticultural..."
Well that is pretty subjective (used a lot in the US, where there is such a huge difference across the country).
"Cool Temperate" is the ecological term for the vegetation zone that most of the UK lies in. It is the area of deciduous forest that runs across Europe. To the south is the "Warm Temperate" or Mediterranean zone, and to the north is the "Boreal" or coniferous forest zone. /via Cool Temperate
"Cool season" crops that do best with daytime highs, max out around 60-70°F, with nighttime lows in the 40s-50s°F and can tolerate light frost. /courtesy of University of Illinois Extension Horticultural Educator, Jennifer Schultz Nelson, Ph.D.
While there's no "definitive" standard, our rough definition ranges from just above the frost threshold up to the mid-70s°F /via Missouri Botanical Garden
Köppen classification system probably best to use. UK is Cfb = maritime temperate with average temp > 10°C in summer etc
