The other zonal denial

Since I don't have a greenhouse or room indoors to keep marginal plants alive when the temperatures fall, I've pretty much avoided growing things above my USDA Zone. But in the spring of 2017, I tried a little zonal denial by planting a beautiful Alstroemeria 'Inca Ice' and a Sarcococca 'Fragrant Valley.' Both of these are plants that typically need a zone warmer than where I live. But these varieties were both listed as hardy for my zone. Alas, they died along with a depressing number of older shrubs and trees in the winter of 2017/18 when we had extremely cold temperatures with little to no snow cover. In fact, our biggest snowfall last season happened in late April.

PHOTO: DEC. 15, 2017

When I look at the print garden catalogs that are now arriving in the mail, I always look to see what zones are listed at the end of a plant's description. When I go plant shopping online, I tend to click on all those special ways of digitally searching — like listings of new plants, rare plants or those that a nursery has hybridized themselves.

Now and then I look at what plants a nursery offers that are specifically appropriate for my USDA hardiness zone. When I used my Zone 5 as a search tool recently, I had a bit of a lightbulb moment. Something I've known for as long as I've gardened in Wisconsin was right there in front of me; I realized I had been seeing it but not really acknowledging it in recent years. 

What I saw were the temperatures that go with a Zone 5 designation:

USDA Zone 5a:  —20° to —15° degrees F.

USDA Zone 5b: —15° to —10° degrees F.

In reality, we recently woke up to a low temperature of -28° with a wind chill of -48°,  significantly colder than the expected lows for Zone 5.

PHOTO: MARCH 2, 2017

According to the map, I live in Z5b. I have an urban garden which makes it a little more protected but I have been ignoring, if not denying, that very cold zonal truth. We've had multiple snowstorms since the Winter Solstice (Dec. 21). They've beautifully covered garden with a deep blanket of snow which I hope was enough to protect everything from the Polar Vortex temperatures we just went through. We had a few days were the temps went up into the mid-40s: a change of 70°almost overnight. Then back to snow and freezing rain and snow again. 

Despite all of our talk about warmer weather as part of climate change, it is the drier winter with little snow cover and cold temps like we had last year that is deadly for gardens like mine. Rather than playing with Z6 plants, I should be thinking about Z4 or even Z3. Time to get real in the garden again. No more planting for hotter summers. It's the colder winters that I need to be thinking about when I go plant hunting from now on.

Comments

[Barbara H.]

It's getting kind of tough to plan and plant, isn't it? What I am finding so disconcerting is our periods in winter where it is unseasonably warm, springlike, encouraging so many plants to break out and say "Yippee! We're still here!" only to suddenly get zapped by a cold snap. Erratic temps are not good!

[Loree / danger garden]

Yikes, Zone 3!? I can't imagine.

[Lisa at Greenbow]

I have had these same thoughts. I am supposedly in z6b. That is crazy when we often get much colder temperatures. We rarely get enough snow to insulate any plant. When we do get snow it is normally gone in just a few days. I don't purchase anything for zone 7 even though I am temped from time to time. I lean more toward the Z5 plants. Our summers are too hot and dry for most plants for colder temperatures. It is often a conundrum as to what to purchase.

[Tracy]

I prefer the Sunset zoning, it takes more into account that just min. temp, like moisture. 50 zones in US. Alas, nurseries don't use it.

[Kris P]

I've found the traditional zonal designations unhelpful. I'm in 10b or 11a now, depending on the source, but then heat, not cold, is the biggest threat in my garden and the summer highs seem to be getting both higher and more prevalent. Sunset Western Garden Book uses an expanded criteria consisting of 24 zones plus 2 zones specific to Hawaii. It's of greater use to me because it deals with both the full range of temperatures, hot and cold, as well as factors like the marine influence, the amount of rain, etc. However, relatively few growers, even here in the western area, use that classification and Sunset's own listings, while substantial, are limited to 9000 plants. Sad as it can be, sometimes experimentation is the only way to know what works, at least in my area.

[Linda Brazill]

Yesterday's high was 41°. It was 2° when we got up a little before 8 am this morning and it is supposed to get up to 16° or a bit higher. Thank goodness for the snow cover but it is hard to know how it will continue to play out before spring gets here.

[Linda Brazill]

Since gardening is the hobby I spend money on and not much else like travel, I am glad that I am able to replace plants or try something different when this weather kills them. But it is the maturity that makes them big enough to enjoy and getting there is more and more of an issue.

[Linda Brazill]

I forget to check Sunset so thanks for the reminder. I am aware in my own garden/climate of moisture for the most part so I pay attention to that. But it is extreme winter cold with lack of snow that is what we are seeing more of these days. And that is a whole new ball game.

[Linda Brazill]

I think experimentation is where all of us are finding ourselves these days. I figure if I go down a zone it may help but we really need deep snow cover for winter plant survival and that is what is changing for us. I think we are all in different seats of the same boat.

[Nell]

Your sterner resolution is a good plan, especially for woody plants. But you do still need to be thinking about the peak heat of summer, especially night-time lows, because many trees and shrubs that will survive z4 winters will fail to thrive if they can't get the cool temperatures they need in the other seasons. They'll be stressed and more vulnerable to insects and diseases.

[Linda Brazill]

You are certainly right about that, which is what is making it harder to figure out exactly what makes sense to plant anymore.

[Cortney D]

I'm a pretty strict zone adherent, but then again I'm zone 4b so there's not too much lower zone-wise I can go. I've grown a few lavender (from seed) with success but every winter is a bit of a guess if they will come out the other side alive.
It is a bit crazy to think that even as we warm up in some seasons, we aren't really warming up on the cold end. Its almost the worst of both worlds!

[Beth @ PlantPostings]

Yes, this is a challenge, isn't it? I'll be curious to see what makes it through this winter, after being surprised about how few plants bit the dust last year. I've been moving more toward native plants. And the new non-natives have to be rabbit-proof (unless I'm willing to pamper them with caging) and very cold-hardy. (I do make a few exceptions, with lowered expectations.) I agree totally with what you and Lisa said--snow is a good thing in the winter.

[ceci]

It was 67 today here in Virginia; very nice for puttering outside but if it were to stay warm for long we would be in trouble. It was in the teens 2 weeks ago, and lows in the 20s are expected next week, its no wonder the plants are confused. Most summers we can expect 6 weeks with no significant rainfall, another big plant stressor. So its hard to plan!

ceci

[rusty duck]

It is a constant balancing act which I'm starting to lose. The problem here is winter wet tolerant vs. increasingly, summer drought.
There is a new Monty Don series (2 programmes) on Japanese Gardens, the first screened here last night. It's very good, hope it makes it across the pond. Raked gravel should survive climate change!

[Peter/Outlaw]

Yikes! Zone 3 winters and hot summers narrows the plant list. It's not the colors on the artist's palette but what she does with them that makes a masterpiece. You, my friend are an amazing artist and your garden reflects that beautifully. It's tempting to urge you to move to a milder climate but as Les Brake, garden designer and plantsman, who moved from a warm Texas garden to zone 2, Willow, AK told me when I asked why he stayed and worked so hard in the frozen north, "A gardener gardens."