What is a cold climate?

– Posted in: FAQ
32 comments
Image of snow covered woodland

This photo was taken two days before the digital thermometer bottomed out in January 2005

Quite a while ago, someone emailed me, asking what was a cold climate. I never did answer them, because I thought it was obvious. A cold climate is any climate too cold to grow the plants you really want to grow. If you live in Austin, and you want to grow pineapples outdoors, obviously your climate is too cold. If you live next door to me, and you want to grow crape myrtles; sorry, you live in a cold climate.

When I started this website, I defined a cold climate as USDA Hardiness Zone 4, because it got down to -30F (-34C) in the winter here. No, not the whole winter–three or four days here, a week there–just enough to kill Zone 5 plants. And as I thumbed through catalogs and consulted reference books (this was before there was much on the internet), it seemed to me there was a big dividing line between Zones 4 and 5, that quite a lot more plants could take Zone 5. It was difficult to find good information on cold hardy varieties, and techniques and tricks to help plants survive, and I wanted to collect the information I found in one central location.

I’m not such a stickler on my definition anymore, in part because I’ve learned that many factors contribute to a plant’s hardiness, and minimum winter temperature is just one of many things to consider, and also because, heh, I no longer live in a cold climate by my own definition. Yes, the coldest it’s gotten this winter is a balmy -4F(-20C), which is Zone 6! The last time it got colder than -20F(-28.8C) was in 2005, so it’s been warmer than Zone 4 for the last three winters.

Meanwhile, in Iowa (and elsewhere) it’s gotten much colder than typical. Seems to me, in these days of global weirding, we need to learn from each other more than ever. What do you think is worse, unusual cold or unusual heat?

About the Author

Kathy Purdy is a colchicum evangelist, converting unsuspecting gardeners into colchicophiles. She would be delighted to speak to your group about colchicums or other gardening topics. Kathy’s been writing since 4th grade, gardening since high school, and blogging since 2002.

In the end, this may be the most important thing about frost: Frost slows us down. In spring, it tempers our eagerness. In fall, it brings closure and rest. In our gotta-go world–where every nanosecond seems to count–slowness can be a great gift. So rather than see Jack Frost as an adversary, you could choose to greet him as a friend.

~Philip Harnden in A Gardener’s Guide to Frost: Outwit the Weather and Extend the Spring and Fall Seasons

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JJacobsen February 13, 2010, 11:36 am

I live in N. Minnesota, and except for Alaska, this is about as cold as it gets. Where I live, what’s even more of a killer than the cold is the soil — hard, clay soil. The soil has so much clay in my yard, I even had to install a mound system rather than a regular septic tank.

Kathy Purdy February 13, 2010, 1:07 pm

That is standard practice in my area, too. Have to go to a lot of expense to install a septic system that satifies regulations around here.

Christine Steendahl October 30, 2008, 12:13 pm

Beautiful photo. Hard to believe things will be looking like that in the not too distant future.

Nori Lane Bishop July 3, 2008, 10:52 pm

One of the first plants that will be recommended to grow in the conditions you describe will be goutweed, or Bishop’s weed, the Aegopodium podograria, native to the Himalayas. However, I’ve spent so much time battling this plant that I can’t recommend it to anyone, no matter what.
The good news is that there are other plants, even some natives, that will perform in this location. Some shrubs that would do the trick: Symphorocarpus (Snowberry and Coralberry); native species of Phododendron rosea; Viburnum opulus, Viburnum prunifolium; Vaccinium (blueberries); Cornus canadensis (bunchberry); Yews; and American Arborvitae. Some perennials that will grow in shade on the north side of the fence: Aconitum (monkshood); Aquilegias (columbines); Aruncus sylvester (goatsbeard); Asperula odorata (sweet woodruff); some asters species; Baptisia australis(false indigo); Cimicifuga (snakeroot); Campanula rotundifolia (creeping bellflower); Convallaria (Lily-of-the-valley); Dicentra eximia (fringed bleeding-heart); Dicentra spectabile (common bleeding-heart); Dictamnus (gas plant); Eupatorium maculatum (Joe-Pye-weed); Filipendula ulmaria (Queen-of-the-meadow); Iberis sempervirens (candytuft); Lobelia cardinalis (Cardinal flower); Mertensia virginica (Virginia bluebells); Myosotis (forget-me-nots); Platycoden (balloonflower); Pulmonaria (lungwort); and Violets.
This list was compiled from Wyman’s Gardening Encyclopedia, pub. 1971.
Good luck and have fun.

Nori Lane Bishop July 3, 2008, 10:50 pm

One of the first plants that will be recommended to grow in the conditions you describe will be goutweed, or Bishop’s weed, the Aegopodium podograria, native to the Himalayas. However, I’ve spent so much time battling this plant that I can’t recommend it to anyone, no matter what.
The good news is that there are other plants, even some natives, that will perform in this location. Some shrubs that would do the trick: Symphorocarpus (Snowberry and Coralberry); native species of Phododendron rosea; Viburnum opulus, Viburnum prunifolium; Vaccinium (blueberries); Cornus canadensis (bunchberry); Yews; and American Arborvitae. Some perennials that will grow in shade on the north side of the fence: Aconitum (monkshood); Aquilegias (columbines); Aruncus sylvester (goatsbeard); Asperula odorata (sweet woodruff); some asters species; Baptisia australis(false indigo); Cimicifuga (snakeroot); Campanula rotundifolia (creeping bellflower); Convallaria (Lily-of-the-valley); Dicentra eximia (fringed bleeding-heart); Dicentra spectabile (common bleeding-heart); Dictamnus (gas plant); Eupatorium maculatum (Joe-Pye-weed); Filipendula ulmaria (Queen-of-the-meadow); Iberis sempervirens (candytuft); Lobelia cardinalis (Cardinal flower); Mertensia virginica (Virginia bluebells); Myosotis (forget-me-nots); Platycoden (balloonflower); Pulmonaria (lungwort); and Violets.
Good luck and have fun.

Wyn June 25, 2008, 7:16 pm

I live in zone 2 and am looking for a non-poisonous shade plant for the north side of my fence. When I entered that info in google it sent me to this site. Lovely pictures and great info, unfortunately not really my zone. LOL.

Karin February 19, 2008, 8:44 am

There are huge differences between cold climates, too. I live in Stockholm, Sweden – I tend to think of this as a cold climate, but the winter temperatures here rarely go below -15 C, placing us in the equivalent of US zone 5 or even 6. We don’t have nearly as hot summers as some much colder US climates do, though. There’s much less of a temperature span over the year; from around -15C at the lowest, up to about 30C at the highest, which means that while plenty of plants are winter hardy here, many of them won’t grow very well anyway, because the summers are too cool.

Kathy Purdy February 13, 2008, 11:03 am

I confess I did hesitate a bit when naming my website, but I needed a title that would encompass many topics. I’d be the first to agree there are places colder than here. Of course, I could also point to places north of here that are warmer. There are a lot of factors that affect climate. And I hear you about the heat! Heat up here always comes with lots of humidity, which makes it worse.

wiseacre February 13, 2008, 10:38 am

I always laughed a bit when going to your site. You want cold come visit me 🙂 I’ve always liked to tell ‘southerners’ it only snows here when it warms up.

For me it was always a problem of low temps and no snow. The cold and frost heaving took a real toll on the plants. While most maps put us in zone 4 I’ve always considered it a 3 to be safe.

One reason I moved north was to get away from the summer heat. Climate change has now pushed that heat up here. For me I’ll always take the cold winters if it means the summers are bearable. There’s more than enough cold hardy perennials to garden with. Not that I don’t wish for a larger variety.

Kathy Purdy February 11, 2008, 6:53 am

Annie, we have years with reliable snow cover, and other years (like this one) where it freezes and thaws, snows and melts. Even when we do have reliable snow cover, we have the entire mud season (mid-March till sometime in May) of freezing and thawing before things settle down.

Annie in Austin February 11, 2008, 1:21 am

A great post, Kathy – with appropriately interesting comments. I always thought of Chicagoland as a cold climate, but it was zone 5A when I lived there so wouldn’t have qualified – we did get down around minus 25 F a few times.

It surprised me to realize that you have so much frost heave – guess I always think of NY State as under snow cover.

When I lived in zone 5, the plants I lusted for were zone 6 or 7… now I can grow plants for zones 8 and try some zone 9 plants, but still can’t grow the elusive sevens – too much heat.

Annie at the Transplantable Rose

Kent February 10, 2008, 6:49 pm

Kathy – I had thought that I’m at about the same latitude as you, but looking at a map just now I see that’s not true. I’m in heat zone 2 thanks to Lake Superior. My growing season is actually longer than one might expect this far north, again thanks to Lake Superior, but by September the days are so short that plants stop growing and just sit there.

When I moved here from Iowa 25 years ago, I had to forget most of what little I knew about gardening. I’ve tried lots of short season varieties of tomatoes with limited success. The best combination of productivity and vine ripening I’ve found is one called Jelly Bean Grape Tomato from Pinetree Garden Seeds.

Kathy Purdy February 10, 2008, 10:37 am

Diana, please do make a list of questions for the Spring Fling social hour. Depending on the question, I might be able to create a handout or provide a list of links to help out. I am planning on bringing my favorite web/blogging books for people to thumb through.

Diana February 10, 2008, 10:28 am

Kathy — Great post — and so true. I love the Henry Mitchell quote, don’t you find that true in so many aspects of gardening, that we are always trying to out-do or out-smart mother nature?!! Either we are eternal optimists or we like beating out heads against the wall! Loved the Austin mention – so funny. We do try to grow into the next zone here all the time, because we get teased with warmer spurts of weather and then all of a sudden, we get a dose of reality. I did live in Minnesota for 4+ years, though, where the coldest it got was -53 wind chill. I think it was -16 actual temp. Brrrr…but it wasn’t the cold that got me, it was the months and months of gray…. Can’t wait to see you again at SF! Pam suggested that I make a list of tech questions!

sherry February 9, 2008, 10:05 pm

I think it’s plenty cold this winter, and I’m OVER it. I’m so ready for spring. If we had snow as pretty as yours, it would make winter so much more tolerable. BUT, so far we have just had cold, yicky, rain. The worst.

Julie February 9, 2008, 6:54 pm

Dear Kathy-
I WISH for more cold. The plants I miss most since moving to Texas are lily of the valley, bearded iris and peonies — all need cooler temps.
February, however, is outasite here!
J.

Kathy Purdy February 9, 2008, 6:07 pm

Dee, we have a lot of trouble with heaving, too, because we can have a warm spell in March and a decidedly cold spell in late April.

Kent, thanks for stopping by. You are right about the snow. Unfortunately we don’t always have snow cover here. I know that Ellen Hornig of Seneca Hill Perennials can grow South African plants that are only rated Zone 6 or even 7 hardiness because of her incredible snow cover. Her free draining soil doesn’t hurt, either. Your growing season must be shorter than ours, or our summers are hotter. We usually manage to grow corn, though we do have to choose an early maturing variety. And we do ripen tomatoes, though most of them ripen after Labor Day. But in general I’d say your synopsis of cold climate gardening is right on target.

Kent February 9, 2008, 11:50 am

[M]inimum winter temperature is just one of many things to consider…” Agreed!

I’m in Duluth, Minnesota, at the western end of Lake Superior. I’ve found that even plants that are marginally hardy in zone 4 will be just fine under a foot or more of snow regardless of how cold it gets.

Cold climate gardening as far as I’m concerned means delayed spring (waiting for the frost to leave the ground, resisting the urge to plant beans and put out transplants before June 1st), a short growing season (forget about growing melons, sweet peppers, and sweet corn), and a lack of heat (the “typical” varieties of tomatoes won’t ripen). There are compensations though – longer days, extended harvests, and extended bloom time.

Dee/reddirtramblings February 9, 2008, 10:04 am

Kathy, I thought you meant gardeners too. As to plants, the ups and downs are most hard on them. In Oklahoma, we have so many varying temps, that we fight plants heaving out of the soil from now through April. Some of the ones who get the worst treatment are the heucheras. They have a terrible time, and if I lose one, it’s because of this.~~Dee

Kathy Purdy February 8, 2008, 9:25 pm

EH, that pretty much echoes my own sentiments on the matter.

Ellis Hollow February 8, 2008, 9:17 pm

I do think we live in a changing climate, and one that is warming. But I also think that the biggest challenge will not be warming so much as instability. While we may be tempted to grab plants from a Zone or two south, remember that it only takes one cold winter to wipe out our experiments with Zone creep.

It’s fun to experiment. But don’t bet the whole garden on Zone creep. Losing a few perennials here or there won’t ruin the scenery. But I’d be more cautious investing in trees and shrubs from warmerZones.

Kathy Purdy February 8, 2008, 7:23 pm

Jim, I am about as landlocked as you can get in NY state, and I live in a cold pocket to boot. And even though my sister lives over 100 miles north of me, because she is on the shores of Lake Ontario, she is still harvesting basil when my plants have been killed by frost. And she has better snow cover.

Kathy Purdy February 8, 2008, 7:15 pm

Carol, I remember that winter. And you probably remember Henry Mitchell saying, “It’s Human Nature, or at least a gardener’s nature (which is not quite the same thing), to want to live at least one and preferably two climatic zones warmer than where he gardens.” I thought about working that quote into the post.

Kathy Purdy February 8, 2008, 7:07 pm

Curtis, Jodi, and Pam: I was asking which was worse for the plants, but you three were thinking what was worse for the gardener!

Pam, I don’t think I’ve gotten much braver. I guess I recklessly plant Zone 5 plants now, but many of them could survive Zone 4, anyway, I think. We still get late freezes even though it doesn’t get as cold in the winter, so spring takes just as long to get here.

Jim February 8, 2008, 3:00 pm

I’m with everyone that doesn’t like the drastic dips in the cold weather. I think that does more harm than hot weather.

Buffalo can get unseasonably cold a few times a winter, but we’re blessed that we’ve got a big air conditioner, called Lake Erie, that keeps our hot summer days moderate. We’ve never hit 100 degrees.

We’re Zone 6a. If you’ve gone from Zone 4 to Zone 6, I should be able to put in a tropical garden!

The Germinatrix February 8, 2008, 1:00 pm

Great post! I have to say I find the cold much much harder to deal with as a gardener – but I’ve only experienced a freeze once, and not being prepared, I lost many tender succulents. While I love many plants that I can’t grow here in Southern California, I think I’d be truly sad if I couldn’t use Agaves or Dracena draco as structure/sculpture.

Carol February 8, 2008, 6:08 am

I remember the coldest day ever in Indiana. They recorded a temperature of -36 F in 1994 about 15 miles south of here. I didn’t like that! I wondered if any of my zone 5 plants would be alive once spring came. So I think unusual cold is worse.

Plus when it is really cold outside I can think “what global warming?” But when it gets really hot, I think, “what! global warming!”

And Kathy, I think there does seem to be a big dividing line between zone 4 and zone 5 plants, but me eye and desire is always drawn toward the zone 6 plants! We all want that plant that is not quite hardy enough for our gardens. Well, with global “weirdness” we might get our wish.

Carol, May Dreams Gardens

Pam/Digging February 8, 2008, 5:30 am

I’ve never lived anywhere that had unusual cold. A frigid New Year’s spent in Boston was my coldest experience, and I don’t care to repeat it. Then again, I’ve spent summers in Houston, and that’s icky too. Do I sound picky? 😉

How interesting that by your own definition you’re no longer cold-climate gardening, Kathy. Have you gotten confident enough in your new zone to try some tender plants, just to see?

jodi February 7, 2008, 11:26 pm

Global Weirdness indeed! Perfect description. And an excellent post, as always. I prefer unusual cold to ususual heat because I don’t like it too hot. Here on the North Mountain looking down at the Bay of Fundy, our garden is often 10-15 degrees F cooler than down in the Annapolis Valley–and that’s on sunny days. On foggy days, it’s much cooler. But I like it that way. In the winter, the Bay usually moderates our climate a bit but we do get some days worthy of zone 4; mostly because we’re right on a hill with nothing between Isle Haute 30 miles down the Bay and us for a windbreak. However, with a little mulch and some microclimates, we get all kinds of things through that wouldn’t cope with longterm zone 4 weather.

Curtis February 7, 2008, 11:01 pm

I would say unusual cold to heat. Thats just me as I dislike the cold weather. My zone is 6 the lowest lows have gotten down to -10 F here. A few times to -12 but just a few times over the years.