Did you hear about the guy who got rid of his old lawnmower? It just wasn’t cutting it.
Besides a good lawn mower, a healthy lawn depends on proper timing of tasks like fertilizing, watering and weed control. The when is as important as the how.
Our lawns in the Upper Midwest consist of types termed cool season grasses, because they grow most rapidly during spring and fall when temperatures are cool and moisture is usually plentiful. These grasses, including Kentucky bluegrass and fescue, become less active during the heat and drought of mid-summer, even becoming brown and dormant if hot, dry conditions persist.
Although our grasses slow a bit in midsummer, the Upper Midwest is still among the best turf-growing areas of the country. To the south of us, the nation’s wide midsection is nicknamed the “crabgrass belt” because conditions aren’t quite right for Northern cool season grasses or Southern warm season types.
In our region, lawns become healthiest if we follow and support the natural growth cycle of our cool season grasses. In spring, roots are long and full of nutrients from last fall. The grass uses this stored energy for spring growth. When summer’s warmer temperatures arrive, leaf and root growth slow down, and plants rest during heat and drought. When temperatures cool down again in early fall, grass becomes highly active, grows with increased vigor and stores up nutrients in the long roots.
Lawn maintenance should match these seasonal cycles to mesh with the grass’s natural rhythm. For example, fertilizer is best applied during the grass’s most active growth cycles in May and September.
The following is a month-by-month lawn calendar based on recommendations from North Dakota State University and the University of Minnesota.
- Rake lawns when turf is dry enough to kneel without getting wet.
- Begin mowing as needed in late April. Grass can be cut shorter during the initial spring mowing.
- Apply pre-emergent crabgrass preventer shortly before the soil temperature reaches 50 degrees, which is a trigger for crabgrass seed germination.
- Seed lawns or repair bare spots after the soil temperature reaches 50 degrees.
- Dethatching, also called power raking, can be done in early May when lawns become stable enough to prevent damage to grass.
- Core aeration, which lifts small plugs of soil and thatch from the lawn, is useful if the lawn is hard-packed from heavy soil, traffic or thatch buildup.
- Fertilize the lawn when it’s green, actively growing and best able to utilize the nutrients applied. Memorial Day is an easy-to-remember target date.
- Spot-spray weeds as they appear. Liquid herbicides are more effective than weed-and-feed products.
- Apply post-emergent crabgrass killer to visible crabgrass seedlings while they are tiny.
- Raise the mowing height to 3 inches for healthiest turf.
- The optimum amount of water for best lawn growth is 1 inch per week, either from rainfall or sprinkling, applied in one application. The amount can be divided between two sprinklings if the soil is light and sandy.
- Maintain a mowing height of 3 inches, which shades grass roots, keeps soil cooler, conserves moisture and is more likely to remain green in summer heat. Low-cut turf becomes hot and dry and turns brown more readily.
- Don’t spray for weeds during summer heat, which can adversely affect grass plants.
- Don’t fertilize in the heat of summer, especially if the lawn has turned brown from hot weather or drought.
- When sprinkling the lawn, water deeply and less frequently, applying 1 inch of water in one application, once per week, to encourage deep rooting. Frequent, shallow sprinkling causes shallow roots and wastes water.
- Continue to water deeply when sprinkling, instead of frequently and shallowly.
- Lawns can be dethatched or core-aerated from late August through September.
- Seed lawns or repair bare spots before mid-month. The first half of September is the most successful time of year for lawn seeding.
- Fertilize around Labor Day, which is the most important fertilization of the season, giving grass plants the nutrition to develop a deep healthy root system and thick turf.
- September is the most effective month for weed control. For hard-to-control weeds, apply herbicide in fall and again in spring or early summer.
- Gradually reduce the final mowing height from three inches down to 1 1/2 or 2 inches.
- Protect lawns from winter vole damage by placing rodent bait or traps in PVC pipe located in areas where vole activity has been observed. Granular fertilizer applied in October might also repel voles.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at firstname.lastname@example.org.