Soil microbes, like all living organisms, need food and energy. In winter, these are not readily available. Annual plants die and perennials reduce growth and consolidate sugars in their roots. With decreased warmth and nutrients, decomposition of organic matter slows as microbes settle into winter.
Many types of bacteria can freeze without harm because they have membranes that do not burst when their internal fluids freeze. With soil rich in humus, bacteria can hibernate through the cold weather well protected. Soil that drains well and has a good organic content creates an ideal environment for microbes in the winter.
Many species of soil fungi do not actively survive the winter. Instead, they release spores. As soon as soil temperature rises, those spores begin to sprout, sending out masses of thread-like hyphae, looking for a food source. Most fungi are beneficial to the soil, breaking down cellulose to produce plant nutrients and humus. Others can be noxious pests, colonizing mulch, depleting nutrients and attacking the grass plant.
Fungal spores causing rusts, blights, wilting, molds, damping off and root rot are everywhere, floating in the air and settling in the soil. Both spores and hyphae can survive winter temperatures
and, if left undist
urbed, can quickly colonize plant roots in the spring. Healthy winter soil, full of beneficial fungal microorganisms, defends tender spring seedlings from attack and gives a boost to early grass plant growth.
Worms can also survive the winter. Before the soil freezes, earthworms burrow down into the subsoil as much as six feet deep. There they form a slime-coated ball and hibernate. Because they are wrapped in slime, they can survive for long periods without moisture until spring rains arrive and wake them up.
Giving your soil the proper nutrients throughout the year will help the beneficial soil life survive the winter. These will, in turn, help you have a healthy, great looking lawn!