When it comes to lawn care, it seems human nature is at odds with Mother Nature.
Minnesotans’ enthusiasm for yard work peaks in the spring, when we’re eager to get back outside after a long winter. But the best time to work on our lawns is right now.
According to the University of Minnesota Extension Service, late summer into fall is the best time to plant grass seed, fertilize, aerate, dethatch and control broadleaf weeds. It’s a great time to lay sod. The only task that’s best done in spring is pre-emergent crabgrass control, which is a nonissue now because crabgrass sprouts earlier in the year.
The cooler temperatures are ideal for renovating or establishing a new lawn. There’s less competition from weed seed at this time of year, and tough perennial weeds like creeping Charlie are vulnerable to chemical control.
Let’s tackle lawn projects one by one.
Probably Minnesota homeowners’ most hated weed, creeping Charlie is hard to eradicate once it’s established. Persistent hand-pulling or energetic raking with a stiff-tined rake will thin creeping Charlie, but every piece of the plant that’s left behind with a root node on it will start a new plant.
If you have creeping Charlie and don’t want to use chemicals, pull it early and often.
Years ago borax was recommended to kill creeping Charlie. That’s no longer recommended. Though borax seems benign — many of us use it at home — it can kill grass if used more than once and may poison the soil so nothing at all grows there.
Weed killers containing triclopyr are most effective against creeping Charlie. Follow label directions, apply in August, and be prepared to apply again about a month later if necessary. It’s a tough weed to kill.
Planting grass seed
Now into late September is a good time to plant grass seed. Buy seed appropriate for the area you’re working on; garden centers usually sell mixes for shade, sun or high-traffic areas. Sun mixes will have more bluegrass, while shade mixes contain more fescues.
You should kill or remove weeds first. Loosen the soil several inches down with a stiff rake or trowel, rake the area smooth and scatter the seed. Gently rake the area. Some seed will be on the surface of the soil, and that’s fine.
Large spots should be covered with burlap or other porous mulches to prevent erosion and to protect from squirrels and birds. Water regularly. The area can be mowed when grass is 3 or 4 inches high.
Because our bluegrass-heavy lawns require lots of water and maintenance, there’s growing interest in low-input lawns that have more fescue in them. U of M turf grass specialist Sam Bauer has more information on this trend here:
While it may take up to a year for a seeded lawn to tolerate traffic, sod gives you instant results. Prepare the area by digging up any dead sod and loosening the soil. Buy only fresh sod, and lay it in staggered rows so the seams don’t line up. Large areas should be rolled to make sure the sod is in contact with soil, but in smaller areas you can walk on the sod after it’s laid, making sure the edges are not curled. Sprinkling a bit of soil between rolls will fill any gaps.
Water regularly, but not so much that the sod is saturated. Gradually cut back as the grass gets established.
One of the things that weakens grass and encourages weeds is soil compaction from lots of traffic. Aeration can help fix that, and fall is the time to do it. Weed seeds are less of an issue then, and aerating before fertilizing will help fertilizer reach the roots. (If you have creeping Charlie, don’t aerate without trying to remove it first — the tines can spread the weed.)
Skip gimmicks like shoes with spikes on the bottom, and use an aerating machine that pulls plugs of grass and soil out of the lawn. Lawn services can do this for you, or you can rent an aerating machine. Aerate after a rain or after the lawn has been watered so the machine can penetrate the ground and pull out plugs. Run over the grass several times in different directions.
While a good aeration makes a lawn look ripped up, grass bounces back quickly, and the plugs deteriorate in a few days.
Lawns can be fertilized from now up to mid-October. Many garden centers sell fertilizer that’s labeled for fall use. At least half of the nitrogen should be in slow-release form, something the label will tell you.
While experts used to recommend fertilizing twice in the fall, research has debunked that. Fertilizer applied after mid-October tends to run off lawns, adding to pollution.
Detailed information from the University of Minnesota Extension Service on lawn care, including topics like dethatching and repair after flooding, is available at: extension.umn.edu/lawns-and-landscapes/lawncare
Mary Jane Smetanka is a Minneapolis freelance writer and a Hennepin County Master Gardener.