What happens to your soil in Winter?
It is generally accepted that once soil temperatures drop below 7°C, biological activity slows to a crawl, and the soil and all its life forms hibernate through winter. By this logic, soil cannot be expected to change for the better during the winter months, and yet it does when given a little help.
One of the rituals that gardeners endure every winter is to periodically brave bitter temperatures and biting winds to check their plants to see what havoc the weather has wrought. But even the most devoted gardeners aren't likely to give much thought to what's happening beneath their feet as they crunch across ground that has become hard as a rock. If they did, they’d probably be surprised.
The frozen soil is still teeming with life but there are plenty of organisms that have evolved to survive the harsh conditions of winter. Prolific among these organisms are the microscopic ones invisible to the human eye. These include bacteria, amoebas and fungi as well as slightly larger organisms such as nematodes and tardigrades — also known as the water bear — and still larger ones such as earthworms.
One of the fun facts about microscopic organisms is that one teaspoon of healthy soil can have more microscopic organisms than there are people on the planet. There are billions and billions of these organisms in the soil year-round. They perform important functions in the garden, and all have developed biological or evolutionary strategies to survive winter. With good gardening practices, home gardeners can help them do that.
Some of the microscopic organisms in your garden die, of course, but even certain fungi or bacteria that that might not survive winter pass on their DNA to the generations to come by leaving spores or reproductive material in the soil: that material will bud and regenerate new organisms once the environment becomes more suitable for growth.