Mulch saves water and weeding
A mulch is simply a covering for the soil. Gardeners have used almost any material as a mulch, including old newspaper, foot-deep straw, grass clippings, tree leaves, roofing paper, and plastic. These and many other materials will work if they satisfy these two basic conditions: The mulch should help to retain water in the soil on hot days, and it should smother weeds. A third but less important condition is that it looks attractive. (Mulch can also insulate plants in cold weather.)
If you leave soil uncovered, hot sun and wind will quickly dry it out, forcing you to water more often. The additional water may also produce unwanted weeds. Another disadvantage of bare soil is that the top layer often gets too hot for good root growth. Even if you manage to keep the soil moist, your plants won’t grow as well as they should.
Three inches of mulch keeps the root zone of a plant cool and moist even in hot weather. Mulched plants may grow twice as big as those without a mulch, produce better flowers and fruit. Plant roots grow thicker, and water won’t evaporate as rapidly. Weeds may grow on mulch surface, are easy to pull out.
Even though sun will heat the surface of a mulch, the soil below is insulated because the mulch holds air. And any moisture in the soil has a hard time evaporating through the differently textured mulch. Because the soil is kept cool, the roots stay near the surface, ready to take fertilizer. Most weeds are smothered, but those that grow are rooted in the loose mulch and come up easily. You should not let mulches build up against the trunk or stem of a plant (commonly called the “crown”) because the trunk may rot if it stays moist too long.You can use any of the materials mentioned here as mulch. When you choose a mulch, consider the following:
• It should be fairly easy to wet. For example, peat moss dries out quickly, and once dry it may become impermeable.
• It should be dense enough not to blow away.
Fir bark is a good choice for a mulch, since it meets all of the above requirements even when finely ground (for certain very windy areas, you may wish to use large chips).
Most organic mulches should be dug into the soil every year or two and a new layer added. Spade the mulch under as winter begins and replace it just before weed growth starts in spring. Where winters are mild and rainy, you may want to replace the mulch immediately to maintain weed control. To measure the effect of mulching, scientists in Connecticut used four different cheap mulching materials around petunias. They used old grocery bags, double layers of newspaper, roofing paper, and 3 inches of grass clippings. The mulched plants grew better than those in bare earth, but those with a grass clippings mulch grew twice as big. There were also more flowers on the mulched plants. Surprisingly, nematode worms (a common pest in some soils) were less numerous under all the mulches except the roofing paper.
One disadvantage of a grass mulch is that it tends to rot and breed flies. A 2 or 3-inch bark mulch is a good substitute for grass.Mulches can also be used around trees, in play areas, or in other areas where you don’t want to plant grass or ground cover but don’t want to pave either. You can use rock, gravel, or the largest size of bark chips. Because these mulches do not shut out light, weeds may be a problem. You can solve it by covering the ground with black polyethylene plastic before spreading the mulch.The same black plastic is also valuable in the vegetable garden. It tends to absorb extra heat and warm the soil, so root growth is fast at the beginning of the season and the amount of the crop is greater at the end.
Before spreading the plastic, prepare the soil by adding a complete fertilizer and watering thoroughly. Leave enough room between the sheets of plastic for planting rows of small seeds (carrots, lettuce, or radishes). For larger seeds (beans, peas, or squash) make planting holes in the plastic. The gaps and holes will let water through, and because moisture evaporation is cut down by the overall covering, you won’t have to water as much.
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Tim Lundie, Editor
