I said it before and I'll say it again: 'The More I Learn...

19 years ago

... the More Confused I Get."

OK, so the latest thing to tax my brain is this:

Since I am zone 6/7, and my garden is a container garden, I always heard that the rule of thumb is to subtract 2 zones when looking for (container-intended) plants that will be hardy to your area. So I therefore thought that, for perennials, I should only look at plants for Zone 5 or below. Yesterday I was looking through a book I have, that shows all kinds of plants and their characteristics. I saw some plants listed as Zone 3-8 for example. Some of these same plants were then described as "moderately frost hardy". Conversely, I saw other plants listed as Zone 6-9 for example, and some of these were described as "fully frost hardy". So I am confused.

The only thing I could think it means is this: one particular plant might be normally found in Zone 6, and while it is "fully frost hardy" (meaning one night of frost isn't going to kill it?), that it could not survive the longer term frosts that would be found in lower zones. And conversely, while another plant might be normally found in Zone 3, if it is only "moderately frost hardy", that might mean that that particular plant, while found in parts of Zone 3, may not survive if it is exposed to long periods of frost?

So am I not only supposed to be looking at a plant's hardiness zone, but am I also supposed to find out how frost hardy it is? Is a plant's zone and its frost-hardiness mutually exclusive?

Thanks!!

Comments (4)

sara_the_brit_z6_ct
19 years ago
I've noticed that sometimes books can be extremely confusing, if not downright sneaky: a plant described as Zone 3-8 but "not fully frost hardy" sounds to me like something that will survive a Zone 8/7 winter, but is probably to be considered an annual in Zone 3/4!

What plants in particular were they? It's always good to cross-check hardiness claims in several books.
Lynn Nevins
Original Author
19 years ago
I can't recall offhand what plants they were, but I do know they were all perennials. And yes, I have noticed that when I get a plant, the zone info on the tag, versus the info I later research online, versus my books at home, often vary by 2 zones for the exact same plant. So I usually go with an "average" of all the zone indications. :--)
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gardener_sandy
19 years ago
The zone info can be very confusing, and to add to that is the fact that every yard has it's own little "micro-climate" areas. On the north side in the shade, you will need to go at least one zone down to get hardy plants, while on the south side in the sun you can go one zone up and still have plants that survive most winters. And to complicate matters further, the heat in the summer also plays an important role in which plants will thrive and which will curl up and cry "uncle!"

Personally, I try almost any plant that is listed as zone 7 (in ANY reference!) in whatever area of the yard seems right for the plant. Zone 8 plants get put in a foundation bed on the south side of the house and so far I've had good luck with them.

Like so many of the so called "rules" of gardening, zones are not set in concrete. If you like the looks of a plant and want to give it a try, find the spot in YOUR yard that seems like the best bet and go for it!
mycalicogirls
19 years ago
This is my take on the haridness info, but I'm not a professional horticulturist. I read those ranges as being a top end and a bottom end...so, zone 3 would be the coldest and you may have the top killed, but still get some root life (our classic here is hydrangeas and many roses, where you have to totally regrow the top each summer) and the top of the range would be the important for plants which need vernalization (winter cold temps) to live. For example, daffodils don't grow well in areas with very warm winters. I hear they don't grow in Texas and Florida, for example.

The Extension Service experts here tell us that no plant will survive in a pot outside over the winter here, but I have hostas sheltered on my front porch in a very large cauldron and they're fine. Molly