Hardiness zones

7 years ago

If a plant is said to be hardy in zones 5, 6, 7, 8, and 9, I assume this means it can tolerate the lowest colds in those zones. Why aren't the higher zones listed? Why would a plant only be hardy to zone 9; what happens in zones 10 and up where lows are even higher? And why don't they just say zones 5-9 or hardy in zones 5 and up? I think I'm missing something in my understanding of hardiness zones.

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rina_Ontario,Canada 5a

7 years ago

last modified: 7 years ago

socks

I am not absolutely sure, but think they list highest zone that plant would do good in. It will, I think, grow in higher zone than listed, but perhaps suffer a bit from high temps. For example Semps: they are Alpine plants, most listed z4-z9. But I think some ppl in higer zones grow them too - keeping them in more shade or having bit of difficulty...And perhaps there isn't enough cold for plants like that during winter -they will survive, but may not be in A1 condition...JMO.

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Comments (6)

Vance Evans
7 years ago
I agree with Rina. I believe those zones might not be listed due to the plant needing a dormancy period and those zones not allowing that period due to temps
socks thanked Vance Evans
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socks
Original Author
7 years ago
Yes, that must be it. It can grow in higher zones but maybe not as well or will need special care, like part sun not full sun, as Rina said.
Rob Blomquist
7 years ago
last modified: 7 years ago
I think of it in relation to the water availability. I think of 10/11/12 as desert zones with little water, and plants that need to have developed a means to deal with the lack of water.
socks
Original Author
7 years ago
I tried some semps in full sun. They did not survive, zone 10a.
cactusmcharris, interior BC Z4/5
7 years ago
socks, no cold period, ergo short lifetime for the semps.

Rob, hardiness zones aren't in any way related to water / lack thereof. It's all about the temps.
socks thanked cactusmcharris, interior BC Z4/5