Why Use Mulch?

by Jim Winkle

Wondering why some gardeners use mulch on their plots? There are many reasons to use a mulch like straw, marsh hay, or shredded leaves.

    • KEEP THE WEEDS DOWN. Once you've weeded your garden, you probably don't want to spend that much time weeding again. Putting a mulch down greatly reduces the need to weed your garden. Weeds that do poke through are easier to pull as the ground stays loose and moist (more on that below). Weeds compete with your plants for soil nutrients; help the good guys win!

    • RETAIN SOIL MOISTURE AND MODERATE SOIL TEMPERATURE. While it generally rains a lot in the spring, it can go weeks in the summer without raining at all. Mulch will greatly help the soil retain water, since it won't evaporate as easily. The deeper you pile it, the more moist it will stay. During dry periods minerals are not as available to plants; keeping the soil moist solves that problem.

      • In addition, mulch helps to regulate soil temperature. This is especially important for shallow-rooted plants. An added bonus: earthworms love a moist environment, and will multiply. They're good for the soil because they help loosen it up, and their castings are food for your plants.

    • PREVENT THE SOIL FROM BEING COMPRESSED. When it rains, it can come down with brutal force. This compresses the soil, which makes it harder for tender young roots to penetrate. Also, root crops like potatoes and carrots like loose soil since they need to displace a lot of dirt. (For these same reasons, it's a good idea to avoid walking in your garden when it's muddy.)

    • INHIBIT VEGETABLE ROT. Cucumbers and other vegetables that touch the ground can partially rot. Put a little mulch under the cuke, and it will be happier. It's best not to mulch a whole area where viney things grow; they often need to put down roots along the vine, and this will be hard to do if the whole area is mulched.

    • WINTERIZE YOUR GARDEN. OK, it's a little bit early to be thinking about this, but some perennials like strawberries need a four to six inch blanket in late November to keep them from getting too cold, and/or to prevent premature thawing in the spring. Mulch carrots, parsnips, and leeks and you can harvest them partially into winter!

Look at the soil in a woods, which has leaves as a natural mulch. It's dark, rich, moist, cool, loose, and full of worms; all things we're trying to attain by using mulch in our gardens. The soil life is fed in a ongoing, slow release way that helps the smaller organisms that build and maintain soil aggregate structure as well as providing additional organic matter as it is incorporated by worms.

Two to three bales is about how much is needed per plot, depending on whether you mulch your paths and how deep you pile it. According to UW Extension publication A3383, mid to late June is a fine time to apply your mulch. Applying it too early to heat-loving plants can slow their growth. In the meantime, keep it dry by covering bales with plastic, or mold will grow in it.

This information pertains to organic mulches. Synthetic mulches like plastic or landscape fabric share some of these benefits, and have some of their own.