Lawn care calendar for Kentucky: when to fertilize and seed

Nitrogen amounts are pounds per 1,000 square feet from the University of Kentucky fertilizing guide; the other dates come from its turf care calendar footnotes, which give no dates for some jobs.

Which grasses grow where in Kentucky

The University of Kentucky says Kentucky bluegrass is only marginally adapted to the state and needs more inputs than other choices. It can work in parts of central and eastern Kentucky, while tall fescue suits the whole state and is the choice for shade, poor soil, heavy traffic and western Kentucky. Zoysiagrass can be a better option in the west. Perennial ryegrass and fine fescues turn up where conditions suit them.

The extension insists on a turf-type tall fescue rather than Kentucky 31 when you buy seed. Its mowing heights are 2 to 3.5 inches for Kentucky bluegrass and tall fescue, 1.5 to 2.5 for perennial ryegrass, 1 to 3 for zoysiagrass and 1 to 2 for bermudagrass, and it raises the mower in summer to reduce heat and drought stress.

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 Louisville International Airport the last spring frost averages March 31 and the first fall frost November 7. At Lexington (Blue Grass Airport) the dates are April 13 and October 28. At Paducah they are April 5 and October 28.

Counting the days between them, Louisville averages about 221 frost-free days and Lexington about 198 (our arithmetic). Louisville's season is 23 days longer than Lexington's (our arithmetic), and the extension separates early April in the south and west from April 15 elsewhere.

Spring

The extension treats spring nitrogen as a make-up feeding: apply it only if none went down in the fall, because too much in spring or summer lowers turf health and invites insects, diseases and weeds. Crabgrass preventer goes on in early April in southern and western Kentucky and by April 15 in central, eastern and northern Kentucky, with a second application in late May if pressure lasts all summer.

Spring seeding is the second choice. The window is mid-February to mid-March and no later than mid-April, with a blooming forsythia as the sign. Spring seedings need a pre-emergent that allows seed, because crabgrass competes, and the extension notes that irrigation and extra care are needed to carry young grass through the summer.

Summer

Mow any time the grass is growing and raise the height in summer. A half rate of nitrogen in late May or early June can help color after a rainy spring. If color is not a concern the guide prefers no spring feeding at all, because crabgrass, goosegrass and bermudagrass respond to nitrogen far more than cool-season grass does, and more spring and summer nitrogen raises the need for irrigation, thatch control and weed killers. The fertilizing guide schedules nothing from June through August, and weed-and-feed products are usually not recommended.

White grub control, curative or preventive, is only for lawns with a history of grubs or where grubs are found.

Fall

Late summer and early fall are ideal for seeding, with mid-August to late September as the best window: cooler temperatures, fall rain, no crabgrass or goosegrass competition and seven to eight months of root growth before the next summer. Sod can be laid in any month the ground is not frozen.

The nitrogen schedule is built on fall. A low-maintenance, mostly unwatered lawn gets 1 pound in October. A medium-maintenance lawn gets 1 pound in October and November. A high-maintenance lawn adds December and the optional late-spring half pound. A very high-maintenance lawn adds September. No single application should be more than 1 pound of nitrogen per 1,000 square feet.

Phosphorus and soil tests

The extension says phosphorus and potassium rates come from a soil test, that nothing should go on if levels are already sufficient, and that a lawn that recycles clippings almost never needs more. I did not find a Kentucky rule that restricts phosphorus in lawn fertilizer: the state fertilizer chapter I opened, KRS 250, deals with seeds, feeding stuffs and fertilizers as products.

Lime goes on only when the soil test says so, since needless lime lowers nutrient availability.

The bag math

The guide shows the sum with a 10-6-4 bag: 1 pound of nitrogen divided by 0.10 is 10 pounds of product per 1,000 square feet. The lawn fertilizer calculator on this site runs the same arithmetic for your bag and the size of your lawn.