So far, 2020 December temperatures have been slightly above average with very little snow across the state. For gardeners growing strawberries, this means you still have time to do one critical task. Before the temperatures drop and snow covers the ground, cover your strawberry patch with 2 to 3 inches of mulch. Also, insulate any container-grown strawberries or bring them to a protected area.
What mulching does for strawberries
Our Minnesota climate is too cold in the winter for strawberries to thrive from year to year without some sort of winter insulation. If left uncovered, winter temperatures below 18-19 degrees F will freeze and injure the dormant flower buds that produce fruit next summer.
Even a couple of inches of mulch over the strawberry plants in the winter is enough to protect the buds from extreme cold.
If you're thinking “I have never covered my strawberry plants in the winter, and they’re just fine,” there could be a couple of things going on.
- First, it is very possible that your plants have been getting injured, but either you have not noticed or you have attributed the low fruit production to something else.
- Secondly, maybe your garden got lucky and didn’t experience the extreme cold temperatures characteristic of Minnesota winters.
- Third, your garden may have had enough snow cover to insulate the plants before extreme low temperatures set in.
Do not bank on a snowy winter to protect your plants against damaging cold.
Types of mulch for strawberries
The most common mulch for strawberries is straw. Straw can be purchased from local garden centers in rectangular square bales. It typically costs about $5-7 per bale, and a bale is enough to cover about a 10-foot-long row of strawberries, 2 to 3 inches thick.
You also could use leaves. It is best if the leaves have been mulched by a lawnmower first; the smaller pieces tend to stay in place better than full leaves when a wind gust comes through. I use two loosely packed wheelbarrows full of mulched leaves to cover 12 square feet of strawberry plants by 2 inches.
What to do with potted strawberry plants
Potted strawberry plants must also be protected from winter temperatures, but the roots must be insulated as well. This makes protecting container plants a bit more complicated than in-ground plants.
One option is to move your container strawberry plants to an area that stays between 20 and 40 degrees F all winter. For many gardeners, this space does not exist in our homes. In January and February, my garage gets well below 20 degrees for multiple weeks.
Most gardeners should consider insulating the roots and leaves with mulch or soil.
If the soil is not yet frozen and you have soil to dig into, you can dig a hole slightly wider than your container and place the container in the hole so that the strawberry leaves are just above ground level. Backfill the hole with soil around the container. Then, cover the strawberry leaves with mulch.
If you are unable to dig a hole for your container plants, then another option is to mound several inches of potting mix or soil around the container in order to help insulate the roots. Then cover the strawberry leaves with mulch.
If your gardening situation prohibits you from insulating container strawberry plants with these (admittedly inconvenient) methods, consider growing day-neutral strawberries instead of June-bearing strawberries.
Day-neutral varieties are meant to be grown as annuals rather than perennials, which eliminates the need to insulate them over the winter.