Answer: Thank you for your question. The goal: keep your lawn as healthy as possible through good cultural practices. This will enable it to out-compete weeds and tolerate the heat of the summer and winter cold. Here are some steps you can take to manage weeds in your lawn without chemicals. Note that these are considered "cultural methods" of management and must be ongoing to be continually effective.
- Re-think your idea of a "perfect lawn". Accept some non-grass plants in your lawn. Dandelions and clover are good plants for bees as they provide early season pollen and nectar.
- Raise your mower blade to 3". Longer grass blades keep plant crowns cool, moist and less stressed during summer heat. Mowing regularly also helps to manage weeds.
- Depending on the size of a weedy area, digging out weeds by hand and re-seeding is sometimes your only option. It is an ongoing maintenance task. You may choose to eliminate areas of grass altogether and re-plant with shrubs, perennials, and trees.
- Water grass deeply and infrequently. The top 5-6" of soil should be moist. This will cause grass roots to move deeper into the soil seeking the water. If you water a little at a time, the water only wets the top few inches of soil. This causes the grass roots to stay at the surface of the soil - where the water is - and thus are more likely to become stressed and dry during the heat of mid-summer.
- Avoid trying to grow grass under trees. Instead, mulch these areas and plant hardy perennials like Hosta, Heuchera (coral bells), and native wildflowers. This approach eliminates thin grass that cannot out-compete weeds. It also eliminates potential damage to tree trunks and tree roots by lawn mowers and weed whips that can lead to tree health issues. Plantings under trees also look really lovely and provide interest in the landscape.
- Fall is a good time to aerate your lawn. Aeration removes soil plugs from the ground, lessening compaction and creating a better environment for grass roots. Local equipment rental shops have aerators or you can hire a landscape maintenance company to aerate.
- After aerating, over-seed your lawn with a soil / compost / seed mixture. In Minnesota, we grow cool season grasses. They are most actively growing in spring and fall. Choose grass seed that is suitable for your conditions (full sun, part sun, shade, etc.). You can purchase this at a local garden center. Note that high quality seed usually costs more. Ask for help in choosing a seed mixture(s) suited to your yard. Some stores can also mix seed for you.