Lawn care calendar for Utah: when to fertilize and seed

Intervals are USU's rotation for northern Utah and for St. George; each irrigation should wet the root zone, and the Division of Water Resources guide assumes about half an inch per run.

Which grasses grow where in Utah

USU Extension says most Utah lawns are cool-season grasses. Kentucky bluegrass suits full sun to partial shade and heavy traffic, tall fescue is a general-purpose grass with more heat tolerance, deeper roots and a little less water need, fine-leaf fescues suit shade and need little fertilizer, and perennial ryegrass is high-maintenance but formal. When buying seed it advises avoiding mixes with annual ryegrass, K-31 tall fescue or Linn perennial ryegrass.

Buffalograss is the low-water native: much less water is needed to stay green in summer, but it is brown in spring and much of fall. USU says common bermudagrass has become a well-established weed in many southwestern lawns, though it is sometimes grown on purpose.

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 Salt Lake City International Airport the last spring frost averages April 8 and the first fall frost October 31. At Logan (Cache County Airport) the dates are May 8 and October 2, and at Cedar City Municipal Airport they are May 21 and September 29. NOAA has no 1991-2020 frost normals for St. George, so St. George dates are not given here.

Counting the days between them gives about 206 frost-free days in Salt Lake City, 147 in Logan and 131 in Cedar City (our arithmetic), so a mid-August seeding in Cedar City leaves about six weeks before the first frost and the same seeding in Salt Lake City leaves more than ten.

Spring

Northern Utah mows from the first active growth until the grass stops in fall, removing no more than a third of the blade at once. USU suggests a minimum height of 2.5 to 3 inches, higher in hot weather, and a last cut of 1.5 inches to limit winter disease. Preventers go on in early to mid spring, before crabgrass and spurge germinate, and cool-season grasses can be seeded or overseeded in April and May.

USU says to test soil every two to three years for phosphorus and potassium, because nitrogen cannot be tested. The standard recommendation is 2 to 4 pounds of nitrogen per 1,000 square feet a year, 1 pound at a time. Aeration is for early to mid spring and for late summer to early fall on cool-season grass, using hollow tines 3 to 4 inches long.

Summer

Irrigation is required to keep a northern Utah lawn healthy. USU's rotation for the north runs every 6 days until the end of April if needed, every 4 days in May, every 3 in June, every 2 in July, every 3 in August, every 6 in September and every 10 days from October 1 to shutdown. In St. George the rotation is every 5 days until April 30, every 4 in May, 3 in June, 2 in July, 3 in August, 5 in September and 7 in October. Water early in the morning, avoid windy times, and check the system monthly for leaks and clogged heads.

The Utah Division of Water Resources publishes a Weekly Lawn Watering Guide built from weather data, assuming about 1/2 inch per irrigation event, plus a Low Water Use guide. On the page I read on October 2, 2026, it reported that the governor had declared a statewide drought emergency on May 21, 2026. Cities set their own rules, so the interval is a target and your city's limits may be tighter.

Fall

Late summer is the best seeding time in northern Utah, since warm soil speeds germination, and USU advises allowing four to six weeks before the first frost. Cool-season grass can go down in August and September, and sod can go down nearly any time of year if water is available and the ground is not frozen. The northern fertilizing months for cool-season lawns are May, September and November.

In the St. George area, USU names late summer the optimum seeding time too, with the calendar marking September to November, and puts cool-season feeding in February and March and in October and November, and warm-season feeding in April, May and August. Pre-emergent goes down in February to March and again in November, and broadleaf weeds are treated in May and June and in October and November.

Fertilizer rules and soil tests

The Utah Department of Agriculture and Food regulates fertilizer as consumer protection: products must be registered and properly labeled. I found no Utah rule that limits phosphorus in home lawn fertilizer. USU says turfgrass in Utah most often needs nitrogen and rarely phosphate or potash, and a soil test settles the question; a test that shows high phosphorus and very high potassium means a nitrogen-only fertilizer such as 20-0-0.

The lawn fertilizer calculator on this site converts that 20 percent into pounds of product for your lawn, so the 1 pound target works for any bag.