||Dr. Gouin's Bay Gardener
Cut It Tall and Let It Fall
Weeds don’t grow in a well-maintained lawn
If you resort to weed killers to rid your lawn of crabgrass, dandelions and plantain, it is likely you are not mowing your grass properly or you are fertilizing it at the wrong time of the year. You also may not have limed your lawn in the past five years.
You can control those weeds by adjusting the height of your lawn mower. If your lawn is mostly bluegrass or fescue, raise the mowing height of your lawn mower to cut at the highest position available, generally between three and four inches. If your lawn is Bermuda or Zoysia grass, set the cutting height of your lawn mower to cut the grass approximately one to one and a half inches. Mow your lawn frequently enough so that you remove no more than one-third of the height of the grass at any one time.
The next important step to a healthy lawn is to leave the grass clippings where they fall. Allowing grass clippings to remain in place reduces your need to fertilize: the grass clippings fall to the ground and compost in place. As the clippings decompose, they release their nutrients back into the soil.
If the pH of your soils is properly adjusted and your mower height is set according to the species of grass you are growing and if the lawn is mowed at least weekly, leaving the clippings where they fall, you’re providing your lawn all the nutrients it needs.
By raising the height of your mower, you allow each blade of grass to produce more food for its roots through photosynthesis. This encourages each blade of grass to send roots deeper into the soil to absorb more water and nutrients. The results are a lawn that is more drought-tolerant and more dense, which means that weeds are less able to become established.
Most weeds that invade lawns, such as crabgrass, dandelions and plantain, are spreading weeds. Most lawn grasses such as bluegrass and fescues tend to be upright-growing plants. A healthy lawn forces spreading weeds to grow upright, which weakens them, and they eventually get crowded out by the healthy grasses. Thus by properly adjusting the pH of your lawn, by properly adjusting the height of your lawn mower and by recycling your lawn clippings in place, you can grow a healthy weed-free lawn without chemicals.
Cut it tall and let it fall.
Professor Emeritus Francis Gouin retired from the University of Maryland, where he was the state’s extension specialist in ornamental horticulture. Follow his column of practical gardening and plant advice every week, only in Bay Weekly. Ask Dr. Gouin your questions at firstname.lastname@example.org.