Mow the grass each week to cut down any weeds that do sprout up and to maintain a healthy lawn. Grass that is maintained is generally denser, shading the soil so that weeds cannot grow and their seeds can’t get close enough to the ground to germinate.
Weeds often get out of control in yards that are not maintained properly. To keep the weeds at bay, you must keep your grass healthy and thick. One way to prevent too many weeds is to frequently mow your grass. Follow a plan with your mowing schedule to kill the weeds and get the lawn you always wanted.
Timing is everything. If you see weeds starting to sprout up, you might want to run the lawn mower over the lawn even if it doesn’t need it. If the blades of grass haven’t grown, the mower won’t harm them, and you can cut the weeds down before they go to seed.
Bag the cut grass blades if your lawn is riddled with weeds, so that the lawn mower doesn’t spray any weed seeds over the grass. The weeds eventually stop growing after repeated cutting, at which time you can allow the grass clippings to be scattered from the lawn mower, adding their nutrients back to the soil to feed the lawn.
Set the blades of your lawn mower at the right height. This depends on the type of grass you are growing. Grass cut too short allows weed seeds to make their way to the soil more quickly and provides them with sunlight. Find the range of height at which your grass should stay, and set the blades at the highest point allowed.
By maintaining your lawn at a taller height, you will have a lawn that requires less watering, and is more heat, insect, and disease tolerant throughout the growing season. Finally, by mowing according to the 1/3rd rule, you will also have to mow your lawn less frequently throughout the year.
While your mower may technically be capable of mowing your lawn from 6-8 inches down to 2 inches every two weeks, it is not recommended. Mowing more than 1/3rd of the leaf blade in a single mowing event can damage the turf plants, making them prone to other stresses such as drought, heat, insect, or diseases.
As an example, when mowing your lawn at 3.0 inches, you would want to mow the lawn when it gets to 4.5 inches (removing 1.5 inches of turf is equal to 1/3rd of the lawn height at 4.5 inches), which would occur about every 7 days for most of Minnesota. But when mowing your lawn at 4.0 inches, you would want to mow the lawn when it gets to a height of 6.0 inches, which would occur about every 10-12 days.
Misconception #2: Collecting or bagging lawn clippings will reduce the amount of thatch in my lawn.
Generally speaking, if you have weeds in your lawn already, there is a very strong chance there are thousands of other weed seeds already present in the soil. These weed seeds can be viable for years or decades, so removing lawn clippings and weed seedheads will likely not actually reduce the amount of weeds present.
Furthermore, by removing lawn clippings from the lawn, you are removing up to 2.0 lbs N / 1000 ft2 per year that the lawn would use to be thicken and reduce weed pressure over time. After all, a dense, healthy turf is the best defense against weeds.
Another misconception with collecting or bagging clippings is that it will reduce or prevent thatch in the lawn. The thatch-mat layer that can build-up over time is made up of partially dead or decaying plant material containing lignin. Turf leaves (which are what we are cutting when we mow) contain little lignin and are easily broken down by soil microbes over the span of a few weeks and do not significantly contribute to thatch.
Some species, such as Kentucky bluegrass, spread by rhizomes and grow a little more aggressively, naturally creating a thatch-mat layer. Other species, such as tall fescue or the fine fescues, do not readily create a thatch-mat layer.