This commentary is by Ron Krupp, author of “The Woodchuck’s Guide to Gardening,” “The Woodchuck Returns to Gardening” and his forthcoming book, “The Woodchuck’s Guide to Ornamentals & Landscape Plants.”
With temperatures increasing due to global climate change, and long dry summers with more frequent storms, our vegetables have come a long way since their ancestors grew in sheltered valleys in Asia and Europe, where the best agricultural land was once found.
In the 21st century, North America’s agricultural land is suffering from wind and water erosion, acidity, salinization, chemical pollution, and the deadening effects of frequent droughts. As average temperatures rise, we need to provide mulching strategies in order to reduce water use, erosion and in maintaining viable plant root systems.
Plus, a layer of mulch can help fight climate change because covered soil holds on to carbon instead of releasing this greenhouse gas into the air.
I’ve been mulching for many years at the Tommy Thompson Community Garden in the Intervale in Burlington. I don’t like to leave the soil bare. Besides mulches, I plant cover crops like annual rye, buckwheat and oats in summer and winter rye in fall to keep the soil covered.
Mulches, like old hay, improve the condition of the soil. As these mulches slowly decompose, they provide organic matter that helps keep the soil loose. This improves root growth, increases the infiltration of water, and also improves the water-holding capacity of the soil.
By using mulch, you don’t have to water as often. In the hot sun, soil tends to dry out faster and harden. And once soil dries out, microbiotic life and earthworms disappear, and water is not taken up when applied. Mulch will help protect the soil from baking in direct sunlight.
Mulch also prevents weeds. Adding it to your planting bed will block light from reaching the soil, which keeps many kinds of weed seeds from sprouting. By adding a thick layer of mulch, you’ll ensure that the weeds never see the light of day!
While an even layer of mulch is ideal, don’t overdo it. The best depth for a mulch layer is 2-4 inches. Any deeper, and it can be difficult for oxygen to reach the soil, which can cause your plants to suffer.
Mulches do not have to cost much. Newspaper, cardboard, old clothes and stones cost nothing. Stones trap moisture when placed around plants, be they lettuce, cabbage, or tree seedlings, but they also attract slugs and snails. Take caution when using stone as a mulch because stones tend to get really hot in the sun. Stones are often used in cactus and rock gardens.
Straw mulch is pricey. Make sure it’s free of weed seeds, otherwise it can cause more weeds than it prevents. (Oat straw is often particularly weedy.) Hay mulch, which is less expensive than straw, is often weedy as well. It’s inferior in quality to straw, as its grown on poorer soil and is most likely mowed later in the season, which gives the grasses and other plants time to sprout weed seed.
When late fall rolls around, check on your mulch and reapply if needed. In the winter, a good layer of mulch acts like insulation, helping to regulate the soil temperature. This reduces stress on plant roots and can prevent frost heaving, where smaller plants are pushed out of the ground as it freezes and thaws repeatedly.
Make sure the ground has frozen a few times before adding mulch as a protective layer for the winter. This is the time I add mulch to my garlic beds.
So, fellow gardeners, by now, it should be easy to answer the question, “Too Mulch or Not Too Mulch.”
