It’s a lot of work. It’s dirty. It’s dusty. It strains our muscles, makes us sore. It’s expensive. It takes time. It takes hours, days. It involves tools and equipment. It takes deliveries and trucks. It takes planning. It requires mathematical calculations. It commits us to lifting and hauling and shoveling and raking. I’m tired already! So…why do we mulch our gardens? Because it’s so good-looking, of course. Wouldn’t we gardeners rather spend a hundred bucks to lay down a rich layer of steer manure than on a new haircut? Doesn’t three inches of compost out-compete a day at the spa? And since the mulch is always deeper on the other side of the fence, we keep at it. Covering the soil with compost, bark, shredded leaves, straw, grass clippings, sawdust and more are common mulching practices. In addition to absolute perfection and beauty in our landscaping, there are a few other reasons to mulch.
Weed Control. One of my favorite quotes from a gardening book is ‘pay particular attention to the presence of horsetail, which will cause years of agony if it finds your landscape.’ Weeds, especially perennials like horsetail, can be agonizing. Those pushy little plants are true survivors. Some weed seeds, like lambsquarter and purslane can survive for forty years! Their malevolent existence competes directly with garden plants for light, nutrients, water and space. Better to leave them in the earth, covered with a thick layer of mulch, than dig them up, closer to sunlight and germination. Studies on commercial vegetable farms (from the book Sustainable Gardening, 2008) show that viable weed seeds in the top six inches of soil average 900 seeds per square foot! Covering soil with mulch will keep the weed seeds where they belong, in the dark and powerless. Weeds seeds can and will blow in and settle on top of mulch, but that’s another story, for another blog.
Water Conservation. November arrives. Storm season is here. Rains pound the ground, carrying away the precious loam and nutrients. Washed down the hill, into the rivers, into the Sound, out into the deep blue sea. We want to keep the soil around our plants and mulch will help hold it in place. A layer of mulch can prevent soil erosion. It holds dirt in the winter and moisture in the summer. During our days of heat and drought in July and August, a few inches of mulch will prevent rapid water loss from evaporation. Soil won’t dry out so quickly, and you won’t have to water as often. So many benefits, such an unassuming title: mulch.
Temperature Moderation. The turn of seasons again. Cold frosty weather can be held back with an insulating layer of mulch. A one to three inch layer protects the surface roots by retaining soil heat. More than three inches of mulch is dangerous. Besides sheltering rodents, it can smother the root system. If it covers too much of the stem/trunk of shrubs and trees it can lead to damage and disease. As the mulch works to maintain soil heat during freezing temperatures, the plants can continue to absorb water, suffering less stress in the winter. Mulch also protects against temperature fluctuations such as freezing/thawing each day, and from desiccating winds.
Disease Control. Clean up your garden! Many pathogens, such as fungal spores, can overwinter in the soil. An example of this is black spot on roses. A layer of mulch in the early spring can shield the new growth from these diseases. Some woody organic mulches, such as sawdust, wood chips or straw will cause a nitrogen deficiency in the soil as they break down. Signs of this are poor growth and yellowing leaves. If this occurs, add a nitrogen fertilizer to compensate.
It looks good! Finally, back to the basics. Why do we mulch? It’s pleasing to the eye, creates a consistent landscape and really good exercise. Also it’s valuable to soil and plant health and keeps those alarming weeds at bay. My favorite is Pacific Garden Mulch, or PGM, from Pacific Topsoils, Inc. It is dark and chunky composted plant material that will add nutrient rich organic matter to our clay soil. Perfect as a layer of mulch as well as a soil amendment. Give your garden a blanket this winter, an all-purpose layer of mulch.