Lawn care calendar for Pennsylvania: when to fertilize and seed

Dates shift with the weather; follow the signs in the text.

Which grasses grow where in Pennsylvania

Penn State lists Kentucky bluegrass, rough bluegrass, perennial ryegrass, fine fescues, tall fescue and bentgrasses as the cool-season grasses adapted for turf in the state. They grow hardest in cool spring and fall weather and may go semi-dormant in hot or dry summer spells.

Warm-season grasses make their best growth in hot weather and are dormant from late fall through early spring. Zoysiagrass is the only warm-season turfgrass with enough winter hardiness to persist as high-quality turf, and only in the southernmost part of the state.

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 Philadelphia International Airport the average last spring frost is April 2 and the average first fall frost is November 10. At Harrisburg International Airport (Middletown) the dates are April 9 and November 2. At Pittsburgh International Airport they are April 23 and October 23, and at Erie International Airport April 26 and November 4.

From Philadelphia to Pittsburgh the last spring frost is three weeks apart on these averages (computed from the dates).

Spring

Spring is for crabgrass control and a moderate feeding. Apply preventer before the weed seed sprouts, using the window for your region: March 15 to April 15 in southeastern Pennsylvania, April 1 to May 1 in most other areas and April 15 to May 15 in the northern tier and high-altitude counties. Broadleaf weeds such as dandelion and ground ivy are best treated in spring or early fall while they are actively growing.

Core aeration suits early to mid spring or late summer to early fall, when the grass recovers quickly. Spring aeration can bring weed seeds to the surface. Dethatch only when thatch is an inch or deeper and the weather is cool and moist.

Summer

Mow at 2 inches or above, as often as the grass grows. Clippings can stay on the lawn if you mow often enough. In a drought the lawn may not need mowing until rain brings growth back.

Penn State advises delaying some practices in extreme heat, drought or cold. Sod can go down almost any time if water is available, but sod laid in hot, dry months needs more frequent watering and takes longer to establish.

Fall

Fall is the strongest season for a Pennsylvania lawn. New seedlings have fewer weeds to fight and get two cool growing seasons before their first summer heat. Seed in late summer to early fall and finish by mid-October.

Slow-release nitrogen goes on in late summer or early fall for lawns fed that way. Fall is also the preferred time for lime, because rain, snow and freeze-thaw cycles work it into the soil. Maintain a soil pH between 6.0 and 7.0.

Penn State Extension and soil testing

Penn State Extension covers turfgrass and lawn care in a set of guides, including a calendar-style article on lawn management through the seasons. A soil test is the only way to learn how much phosphate and potash the turf needs, because nitrogen need cannot be measured that way.

Penn State's lab is the Agricultural Analytical Services Laboratory. Test kits come from county Extension offices, or you can print the submission form and send your own sample. The lab measures pH, lime requirement, phosphorus, potassium, magnesium and calcium. Take cores 4 inches deep for lawns from 8 to 10 places and mix them.