If you’ve got perennials and you want to give them the best possible chance of overwintering, this tip is for you! We’ve found it very valuable to cover many of our perennials with 2 to 4 inches of straw, prior to the cold temperatures setting in.
What this does is create a second insulation barrier. It’s not actually the straw that insulates, but rather the air within the straw that creates an insulative effect. Furthermore, the snow itself creates another surprisingly effective layer of insulation against the cold temperatures. For some of our perennials, especially our most valuable and more “dicey” zone 2 & 3 perennials, this extra effort can make the difference between survival and not.
We normally do this a little bit earlier in the season, but with our late season, it was one of those things we let slip a little bit later. Honestly, it doesn’t make much of a difference if you do it after first snowfall like we have this year. The early cold and even snow isn’t what puts the plant at risk. It’s those -20F, -30F, -40F and even colder temps that we see through the depths of winter that create the most risk for our plants.
We definitely pick and choose the plants that we protect and those we let fend for themselves. Not every perennial gets this treatment! We primarily do it for our food producing perennials like strawberries, asparagus and horseradish. Chives could practically survive on Mars, so no need to protect those. Likewise, we also don’t protect our fruit bearing bushes, such as currants, raspberries and Saskatoons since these are quite hardy and extremely resilient against cold temperatures.
In the spring, we’ll remove the straw once the snow largely melts from the beds. We are able to compost the straw very effectively, meaning this investment doesn’t just go to waste. You can also save the straw over a few years, but it will break down and get a bit icky starting in the second year. You can probably see some of the dark spots in our straw, that’s because it’s two years old at this point.