Lawn care calendar for Michigan: when to fertilize and seed

Spring and fall dates move with the weather; degree days and soil temperature are the better guide.

Which grasses grow where in Michigan

MSU's guidance assumes cool-season turf. Kentucky bluegrass is the default across most of the state. Turf-type tall fescue is the suggestion for people who want better drought tolerance in a full renovation, and MSU advises passing over standard Kentucky 31 tall fescue for home lawns because of its wide blade.

Seeding rates from MSU: Kentucky bluegrass overseeding 1.5 to 2 pounds per 1,000 square feet, mixes with perennial ryegrass or fine fescues 3 to 5 pounds, and tall fescue 6 to 8 pounds, worked into the soil about a quarter inch deep.

Frost dates from NOAA

Dates are the NOAA 1991-2020 normals for the last spring and first fall 32 F freeze at 50% probability. At Detroit Metropolitan Airport the average last spring frost is April 20 and the average first fall frost is October 27. At Grand Rapids the dates are April 29 and October 20.

Our arithmetic: Detroit has about 190 days between those dates and Grand Rapids about 174, so west Michigan loses about two weeks of frost-free season. The northern Lower Peninsula and the Upper Peninsula, which these two stations do not cover, are shorter still.

Spring

Crabgrass germinates when the top two inches of soil sit around 60 to 70 F, and 80 percent of it comes up in that range. A pre-emergent must be down and watered in before then. MSU tracks this with growing degree days from February 15 on GDDTracker and gives an optimum window of 250 to 500, which lasts at least two weeks in a normal spring. In 2026, East Lansing had 318 by March 29. Forsythia bloom is the visual cue.

Do not combine seed with weed-and-feed or crabgrass preventer. For reseeding in spring, use starter fertilizer at about 1 pound of nitrogen per 1,000 square feet, with a nitrogen to phosphate ratio near 1:1 to 1:1.5, and wait for three real mowings, or at least 60 days, before any herbicide. MSU lists high mowing, returned clippings and adequate fertilization as the base of crabgrass prevention.

Summer

Mow at the highest setting your mower has, which MSU puts above 3 inches, to shade the soil and starve weed seeds of light. For a lawn that is also meant to feed pollinators, MSU says to apply at least 2 pounds of nitrogen per 1,000 square feet a year.

If weeds are in bloom, MSU says to mow the flowers off before applying a pesticide, or to pick a product that does not harm bees.

Fall

Fall is the season to rebuild: warm soil, cooling nights, short days that keep seed from drying out, and few annual weeds. Thin lawns with baseball-sized bare spots can recover with a fall feeding. Patches the size of a soccer ball or larger need seed, and a slit seeder in two directions gives the best seed-to-soil contact. Spread a thin straw mulch, about a bale per 1,000 square feet, so a third to a half of the soil still shows.

Early October is the best time to treat ground ivy, dandelion and clover, because weeds are moving energy into their roots. Fall is also MSU's preferred season for core aeration and dethatching, especially when thatch is thicker than half an inch.

Michigan's phosphorus law

Public Act 299 of 2010, in force since January 1, 2012, bars phosphorus on residential and commercial lawns unless a soil or plant tissue test shows a need or you are establishing turf from seed or sod. Biosolids, manure products and other natural fertilizers are limited to 0.25 pound of phosphorus per 1,000 square feet per application. Fertilizer cannot go on frozen or water-saturated soil, spills on hard surfaces must be cleaned up promptly, and MSU adds a 15 foot setback from surface water.

For starter fertilizer on new turf, MSU lists a limit of 1.5 pounds of phosphate per 1,000 square feet in one application and 2.5 pounds a year. The lawn fertilizer calculator on this site shows how many pounds of a given bag deliver that nitrogen figure, which keeps a starter application inside those limits.