Let’s discuss an important winter preparation for subarctic perennials. If you’re on the edge of a growing zone or putting in new perennials in extreme cold climates, like we are, this can be the make or break thing that results in survival of your valued perennials!
For particularly high value perennials, we opt to put several inches of straw over the beds and plants for insulative benefits. It’s not actually the straw providing the insulation, but rather the air barrier that it creates providing the insulative benefit. Snowfall will cover this straw, providing another layer of insulative protection. Just like with greenhouses, these insulative benefits “stack” upon one another.
Our primary focus here is to protect plants that are slightly outside of the growing zone we live in. For example, our property usually experiences zone 2 temperatures and we’d be “classified” as zone 2, but we successfully grow a number of zone 3 perennials. It’s this kind of protection that creates a small “zone 3” microclimate that allows these perennials to survive.
This is also a valuable technique to employ with first year perennials, regardless of hardiness levels. Since these plants still have limited root systems, anything we can do to give our plants a fighting chance to survive their first year will be of benefit. We’ve observed that this greatly aids our first year survival rates.
It’s probably important to communicate that we don’t go “overboard” with this method, it’s very much in a triage type of stance. Some perennials we’d prefer to be “on their own” as we want them to prove themselves against our extreme climate. Often, we’re looking at perennial cost or contribution to our food supply as measures of “value” for whether this protection is desirable. Also, plants like chives might survive on Mars, so there’s no need to protect them.
Although straw input does have a cost, it’s not entirely wasted. This material can be easily composted the following spring, and is loaded with carbon, so it ultimately becomes a garden input. It’s also possible to re-use the straw, if it’s well taken care of. Which means keeping it dry and reasonably protected, but we see our “dry space” as too valuable to use for straw.
One can use other inputs for this same kind of protection as well. Fall leaves are an example that will provide similar benefit. If you have a lot of fall leaves and are raking them up anyway, this is a potential use for them. In our case, we don’t have easy access to easily collected leaves, so straw is the better input for us.
We’ve proven this method to ourselves, many times. Even through the rare winters where we’ve dipped into zone 1 temperatures for periods of time! While it’s hard to “prove” the effectiveness of preparatory techniques like this, having perennials survive two zones below their rated survival is compelling evidence. Thus, it’s a prep we do not skip!
