Lawn care calendar for Maryland: when to fertilize and seed

The source calendar gives its planting dates for central Maryland.

Which grasses grow where in Maryland

University of Maryland Extension says that for most Maryland lawns the dominant grass is either tall fescue or zoysia, and that you should base care on whichever dominates a mixed lawn. Cool-season grasses (tall fescue, Kentucky bluegrass, fine fescue) are fed late summer into autumn; warm-season grasses (zoysia, bermudagrass) are fed late spring into summer.

Mowing heights from the extension: tall fescue 3 to 4 inches, Kentucky bluegrass 2.5 to 3.5, fine fescue 3 to 4, zoysia 1.5 to 2.5 and bermudagrass 1 to 1.5. Fine fescue lawns can go unmown for long stretches, and the extension says to cut at 4 to 5 inches once spring seed heads turn brown. Mowing the last time of the season half an inch shorter helps against snow mold.

Frost dates from NOAA

Dates are the NOAA 1991-2020 normals for the last spring and first fall 32 F freeze at 50% probability. Baltimore-Washington International averages April 10 and October 31. Salisbury-Wicomico Regional Airport on the Eastern Shore averages April 10 and October 30.

Our arithmetic: both stations have about 203 to 204 days between those dates, so a single central Maryland calendar fits both.

Spring

For tall fescue, skip spring fertilizing if you fed one or two times last autumn. A single spring application is warranted for weak, sparse or heavily used lawns, or ones with a history of crabgrass or red thread, and the window is April to about mid-May, or Memorial Day in a mild spring. Weed-and-feed products count against your yearly nitrogen limit, and the extension advises against them.

UMD says herbicide should be a last resort, including pre-emergents, and a pre-emergent usually blocks seeding in the same season. Check local rules too: Montgomery County restricts lawn pesticides. Seed in spring only if the project cannot wait until late summer, and not until soil warms, about mid-April in central Maryland.

Summer

Established tall fescue goes dormant in hot, dry weather and turns brown, which is normal. Skip irrigation or water just enough to keep roots alive in a prolonged drought, and do not mow or fertilize dormant grass. Grass in active growth does best with about 1 inch of water a week, which soaks about 6 inches deep; water in the morning to limit disease.

Zoysia is very drought-tolerant and shows stress by turning paler and not springing back after being stepped on. Feed it a second time only if the lawn was planted at least a month earlier or has poor vigor, and no later than mid-August to reduce winter injury.

Fall

UMD's tall fescue calendar for mid-August to mid-October: control weeds, apply lime and fertilizer by soil test, core aerate compacted areas before overseeding, and sow seed or lay sod no later than mid-October. Seed takes about two weeks to germinate, and killing frosts in November can damage young seedlings. Its nitrogen table for tall fescue is 0.7 to 0.9 pound per 1,000 square feet in September and again from October through November 15, with up to 2.7 pounds a year, and an optional 0.5 to 0.9 pound in May or early June.

From late October to mid-November, mulch fallen leaves with the mower or move them to beds, then fertilize before November 15. The extension warns that using fertilizer to melt ice breaks the state's law.

Maryland's Fertilizer Use Act

Agriculture Article section 8-803.5 covers anyone applying fertilizer to property that is not used for agriculture. No fertilizer containing nitrogen or phosphorus on turf before March 1 or after November 15, or when the ground is frozen, and none on an impervious surface. Keep 15 feet back from surface water, ponds, lakes, rivers, streams and ditches, or 10 feet with a drop spreader, a rotary spreader with a deflector or a targeted spray.

A person other than a professional applicator may not apply more than the University of Maryland's annual recommended rate, and fertilizer may not exceed 0.7 pound of water-soluble nitrogen or 0.9 pound of total nitrogen per 1,000 square feet per application, at least 20 percent slow-release. Phosphorus on turf is limited to cases such as a soil test taken within three years that shows a need. Lawn fertilizer sold for established lawns must be low in phosphorus under section 6-222. The lawn fertilizer calculator on this site shows how much of a bag stays under 0.9 pound of nitrogen for your lawn size.