One of the best ways to prepare the garden for winter is by piling a layer of organic mulch onto your flowerbeds. This is especially important in regions of the country where snowfall is unreliable, which often leaves the ground bare and plants exposed to weather extremes.
Insulate the ground
Surprisingly, rather than keeping the soil warm, mulch acts like a deep blanket of snow to keep the cold in the ground, moderating fluctuating temperatures so that plants remain safely dormant all winter long. This protects roots from freezing during sudden cold snaps and thawing during mild spells, a cycle that can heave plants from the ground, damage roots and place plants under stress.
In most parts of the country, leaves are plentiful—if not in your own garden, then in a neighbour’s—and most make excellent mulch. But, not all leaves are alike. Small leaves from trees such as birch, gingko and lindens are beneficial because they allow rainfall and natural moisture to percolate through to the soil surface, ready for plants to absorb in the spring. These kinds of leaves also decompose more quickly than larger ones once the ground warms, adding nutrients to the soil and improving its texture. On the other hand, the large, leathery leaves of Norway maples, for example, mat together to form a barrier that blocks out water. If only large leaves are available in your area, shred them with a shredder/chipper or leaf-eater/shredder, or spread them on the lawn and run a mower over them.
In areas where leaves are scarce, straw makes a good organic insulating material (stay away from hay, which often contains weed seeds). However, it breaks down very slowly and adds few nutrients to the soil, so remove the mulch as soon as the ground warms up in the spring. Evergreen boughs offer good winter protection, too. They’re especially effective when gently placed over marginally hardy plants as well as alpines, which demand good drainage.
Time it right
Because the goal is to hold the cold in the soil over the winter, mulch should be applied as soon as the ground freezes. Earlier than this and rodents, such as mice and voles, will bed down in this cosy winter home and munch on succulent plant roots. It’s also safer to wait and mulch around the trunks and stems of trees and shrubs while they’re dormant because it reduces the risk of creating conditions where fungal diseases can thrive. To effectively protect your flowerbeds, apply a deep layer of between six and 12 centimetres of mulch. Once the ground starts to warm up in the spring, remove the mulch and reserve it for compost, which can be reapplied to the beds in the summer to help retain moisture in the ground and keep weeds under control.
Lorraine Flanigan is a freelance writer and editor with a passion for gardening. You can read her personal gardening journal at City Gardening.