Just like you, I put a lot of time and effort into creating deep, fertile soil for my homegrown vegetables. As fall turns to winter, my efforts focus on holding onto what I have, which means covering all exposed soil with mulch for the winter. Organic mulches cushion the soil from compaction and erosion caused by heavy winter rains while safeguarding the soil’s storehouse of nutrients. In addition, winter mulches can enhance the cold tolerance of perennial vegetables, herbs and fruits, helping to insure a strong comeback in spring.
In autumn, the most widely available organic mulches include leaves, compost, pine needles, wood chips, sawdust, and evergreen boughs. Which mulch should you use where? One of the advantages of using the GrowVeg Garden Planner is that you can decide now where you will plant your main crops next year, and tailor your winter mulching to suit the needs of the bed’s future residents. For example:
- Vine crops like squash and pumpkins can be sown or transplanted into a plot prepared the previous fall and mulched through winter with leaves. Because you want the leaves to persist into the next growing season, there is no need to shred them, though coarse chopping with a mower helps keep leaves from blowing about. Research has shown that leaf mulch leads to bigger, better pumpkins, with radically reduced problems with weeds.
- Tomatoes and wood chip mulch doesn’t sound like a likely partnership, but as more gardeners are using wood chip mulch (which often can be obtained free from tree trimming crews), reports keep coming in on the glories of wood chip-covered garden beds. When allowed to decay at the surface, the chips host a huge range of fungi, which enrich the soil along with the decomposed wood chips. Best of all, a perpetual wood chip mulch provides poor habitat for slugs and small rodents compared to most other materials.
- Strawberries thrive when given a moderate mulch of pine needles or straw in late fall, after they have stopped growing, with more mulch added in spring. Sawdust also makes a fine winter mulch for strawberries, as well as blueberries, raspberries and other small fruits.
Beds where I plan to grow broccoli, spinach and other heavy feeders get the best winter mulch of all – four or five layers of whatever organic materials I have on hand – leaves, rotted sawdust, garden waste, etc., -- stacked and dampened until it’s about 6 inch (15 cm) deep. Then I cover the moistened mulch with a piece of burlap or old garden blanket to create comforter compost – a quilt of biodegradable materials that can be turned under or raked aside in spring.
The folks at the Interbay P Patch Community Garden in Seattle, Washington, take such layered winter mulches even higher with Interbay mulch, wherein beds are stacked with mulch up to 18 inches (35 cm) deep, and then topped with burlap coffee bags. Covers that block light are a special aid to decomposition because they provide good conditions for microorganisms that need darkness to thrive.
Gardeners who grow perennial flowers are familiar with the practice of placing boughs cut from junipers and other evergreens over dormant plants, which protects the crowns from ice and harsh winter winds. I find evergreen boughs equally effective when placed over marginally hardy herbs like rosemary and parsley. Evergreen boughs also can help nurse hardy veggies like spinach through winter, because they shelter the plants while still admitting filtered light.
In home vegetable gardens, tunnels covered with row cover, plastic, or cloth (such as thrift store window coverings) keep soil safe through winter, just like mulches. Tunnels generally keep soil warm and dry compared to surrounding soil, too. While not exactly mulches, tunnels made from cloth or row cover attached to wire arches are a winter treatment worth considering for beds you plan to use for your earliest spring plantings.
Especially in small gardens, don’t forget that pulled plants, piled on the garden’s surface, can be the easiest way to mulch some beds in winter. Until you move the debris piles to a larger compost heap in early spring, each little mound of decomposing material will serve as an oasis for earthworms and other soil-building critters. Little piles of garden garbage also make great habitats for field crickets, which have huge appetites for weed seeds.
Last year we had an unusually snowy winter, and snow can double the beneficial effects of any mulch by maintaining steady temperatures at the surface. But snow cover is always an iffy proposition compared to winter mulching - the most dependable way to safeguard precious garden soil between now and spring.
By Barbara Pleasant