“Poor mans fertilizer” – this is what people used to call a heavy layer of winter snow, and particularly a late spring snow. You may be concerned that the bitter cold and heavy snows of this winter have killed your perennials, but in fact, we may have a vigorous blooming of bulb flowers and perennials this summer because of it. A deep layer of snow acts as an insulator, keeping the ground at an even temperature and protecting plants from sub-zero temperatures and icy winds. In a more typical winter we would see a pattern of cold and snow then a thaw, cold and snow, then a thaw. While periodic thaws make it easier for us to remove snow, drive, and otherwise get around, fluctuating ground temperatures cause movement in the soil which can expose plants roots, bulbs, or rhizomes – leading to plant death due to cold or exposure to animals. Since we have had snow covering the ground since early December (or before; snow fell all over West Michigan before Thanksgiving this season) we can be fairly certain that plants are where they were in the fall and have been protected by a generous snow mulch.
Snow also contains nitrogen, a greater amount now than in the past because of air pollution. When precipitation comes down in the form of rain, it passes through the topsoil too quickly to fix the nitrogen and can leach nutrients out it, but the melt of accumulated snow lasts longer and can be absorbed by lawn plants that need more nitrogen than whats generally available to them.
One final way that a cold winter is better for plants than a warm one is that many plants require a cold period of dormancy followed by a warm up to germinate well. Thats why a late spring snow can be a blessing – its like a second wake up call for seeds that might not germinate otherwise. Bitter cold will also lessen populations of plant predators including insects and rodents.
While it may seem that winter has taken large toll on Michigan this year, good things may come of it, if we have the patience to wait for and observe them. Deep winter is a great time to start planning changes to your landscape and garden. Get out your catalogs and start dreaming!