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Will the recent Alaska cold snap affect spring planting? Here are some possibilities.

  • Author: Jeff Lowenfels
    | Alaska gardening
  • Updated: April 15
  • Published April 15

Wow. I just don’t know what to say, Alaska gardeners. Um, cold weather is expected in Alaska and is always followed by warmer weather? Or, this is why it is hard to predict if something from zone 5 is really going to be hardy in our gardens? How about, this is unusual? Of course, I could always fall back on wondering what last week’s low temperatures this late in the winter will do to the spruce bark beetle?

AGGGH. And now it is above freezing. What is going on with our weather this month? What we have right now is normal, but last week’s cold snap?

We all have our theories. If you are paying attention to gardening and farming start and end dates, you know global warming is happening in Alaska with very demonstrable certainty. You don’t double the length of a growing season in 100 years unless things are warming.

The simple facts of the matter is that climate change comes with extremes at both ends of the weather spectrum. The “April Cold Snap of ’21” will be remembered as one of the extremes. We can only hope that we get one on the other end of the spectrum this summer. It was just recently, in 2019, when we had a 90-degree Fourth of July in Anchorage, a extreme at the other end of the spectrum. We better get used to the swings.

I get asked, but have no idea what this cold weather will do insofar as gardening is concerned. The odds are the soil will be warm enough to safely plant in it by the later part of May. Remember, soil temperatures rule once things get above freezing — which they will from here on.

OK, let’s do consider spruce bark beetles for a moment. Contrary to an impression I may have left a month or so back, they are native to Alaska. They survived these extremes in the past. I don’t expect we will see the current infestation in Southcentral die off because it was extremely cold last week. Bummer.

However, one way a spruce becomes weakened is to endure an early thaw, followed by a cold snap. The tree starts to wake up and grow and then it gets hit by a cold snap. This is not the case this year. We have not had a thaw yet, and once the cycle begins, it is late enough in April to assume it will not freeze up again. Let’s hope those old trees get some benefit from this and are stronger going into this year’s beetle season.

As for your garden beds, while we have had an extreme cold snap, we are lucky in that we still have a nice — am I really saying this in April? — 2-foot insulating blanket of snow. I doubt things in the soil even knew the air was an unseasonable 7 degrees.

Even better, there is a zone just below that snow where the soil, grass and debris is not fully frozen, and microbes are able to work away. When we don’t have snow cover, this is not so. This means if you put leaf mulch on your beds, it is being turned into fertilizer the organic way, even as you freeze.

The same thing is going on in your lawn. Hopefully you mulched up the leaves that fell on it. If so, right now they are being decayed and the microbes they are feeding under that snow are going to green up your lawn all summer long. No need for Scotts (which, I might add, has a horrible glyphosate ad running this spring. There may be snow on the ground, but Alaskans sometimes need to be reminded we are organic, spring, summer, fall and late winter.)

I digress. This snow cover has kept your perennials from growing. Imagine what would have happened to your plants had we not had snow cover last week? One year a couple of decades back, Southcentral gardeners lost half or more of their perennials to a late cold snap without snow cover. It is one reason I insist on using fall leaves for mulch in the fall.

So, it has been cold. Now it is seasonably warm. Not all is lost. In fact, probably nothing will change and gardening will go on as it always does.

Jeff’s Alaska garden calendar for the week

Flower seeds to start: Asters, nicotiana, cleome, iceplant, zinnia, salpiglossis

Vegetable seeds to start: Broccoli, cauliflower, kale, cabbage

Herbs to start from seed: Summer savory

Alaska botanical garden: Join today. Check out all of the classes and workshops offered. These sell out fast.