The miracle of mulch: It protects roots, conserves water

Mulch works miracles in the summer garden.

Mulch for vegetable gardens is simply organic matter spread on top of the soil around plants. It works best in a layer about 2 inches thick. At that depth, it will act as an insulating layer to keep the root zone of plants ideal for growth.

Mulched soil won’t swell and shrink, crack or create a water-repelling surface crust. It remains evenly moist under this airy cover that blocks surface evaporation. Water you apply remains in the soil to be used by plants. Water trapped in the mulch itself further enhances this benefit. It means you won’t need to water so often, which means mulches reduce maintenance, too.

Mulched soil never receives direct sun because it’s always shaded by that thick layer of organic matter. Roots in mulched soil rarely overheat, making the plants more resilient in high heat or wind.

Every weed seed in your garden is just waiting for you to give it enough water to grow. But if that seed is buried under 2 inches of mulch, it may sprout in darkness, but won’t grow because the mulch cuts off light. This is why decorative mulches are used in ornamental gardens as weed control. When mulches are used in the food garden, they do the same thing so you won’t have to weed.

It’s never too late to mulch. Start with the aisles, then move into your started seedlings. Keep the mulch 1 inch clear of the plant stem.

Vegetable-garden mulch is cheap because it isn’t a decorative thing, so don’t buy ground bark or other bagged materials. Try a bale of straw, which generally runs from $3 to $6 at feed stores. A single bale should be more than enough to cover a large garden, and it fits in the trunk of most midsized cars. Once the bale is open, break apart the flakes and spread the straw into an even layer, then water it down.

Hay for livestock feed becomes unusable if it gets wet and moldy. You can pick up cheap or free spoiled bales of straw, hay or alfalfa from farms, ranches and feed stores. You might even find free bales at the end of agricultural fairs and picnics where bales are often used for seating.

Consider baled alfalfa a superior mulch. Alfalfa is a legume, and every part of these plants is rich in nitrogen. In fact, farmers grow legumes in their winter fields so they can till the nitrogen-rich plants back into the soil before spring planting. The process is called green manure. If you till alfalfa mulch into the soil at season’s end, you reap the very same benefit. Alfalfa can cost from $15 to $20 a bale, but spoiled bales may be far less expensive. This is literally green gold for your garden.

Other mulches you might find in bulk include pine needles, but do not till these in because they are highly acidic. Wood ground up in a community chipping program or carpenter’s wood shavings are also usable but they offer no nutrients and take a long time to decompose. In some regions agricultural byproducts such as rice hulls can be obtained from processing plants.

For a truly sustainable garden, make sure you provide plenty of mulch. You’ll save water, labor and money.