Lawn care calendar for Missouri: when to fertilize and seed

Timing is for central Missouri and can vary by two weeks or more across the state and with the weather.

Which grasses grow where in Missouri

MU's calendar covers the cool-season grasses: Kentucky bluegrass, perennial ryegrass, tall fescue and fine fescue. For zoysia and bermudagrass lawns it points to a separate guide, G6706. Perennial ryegrass and the fine fescues other than tall fescue should not be grown alone without irrigation, because they bunch in drought, and perennial ryegrass alone often does not survive a Missouri summer. Annual ryegrass is not a suitable turfgrass here.

The Missouri Botanical Garden, writing about the St. Louis area, says warm-season zoysia and buffalograss are brown from mid-October to mid- to late May, and that zoysia and bermudagrass invade fescue lawns, showing as brown patches from fall through late spring.

Frost dates from NOAA

Dates are the NOAA 1991-2020 normals for the last spring and first fall 32 F freeze at 50% probability. St. Louis Lambert averages April 2 and November 4. Springfield averages April 9 and October 27, and Kansas City International averages April 13 and October 24.

Our arithmetic: St. Louis has about 216 days between those dates, Springfield about 201 and Kansas City about 194. Kansas City starts spring about 11 days later than St. Louis and ends fall about 11 days sooner.

Spring

March is for broadleaf herbicides on perennial and winter annual weeds not controlled in fall, overseeding thin spots, a soil test and, before growth starts, power raking or mowing off old growth. In April, apply 0.5 to 1 pound of nitrogen per 1,000 square feet, preferably slow-release, begin mowing, and aerate if thatch is heavy or soil compacted. MU says crabgrass preventers go on by April 15.

No nitrogen after May 1: quickly available forms late in spring encourage foliar disease. Seeding in spring is much less successful than seeding in fall, because crabgrass is a major competitor.

Summer

Start watering as needed in June. Water infrequently, to a depth of 6 inches, and avoid puddles. In July, irrigate only enough to stop wilting, about 1 inch of rain or irrigation a week, two to three times a week and between 6 and 10 a.m. in hot, humid weather. Tall fescue has the deepest roots and stays green longest without irrigation, while Kentucky bluegrass goes dormant and thickens again when rain returns, usually in September.

Mowing heights in MU's table: tall fescue 2 to 3.5 inches in spring, 3 to 4 in summer and 2.5 to 3.5 in fall; Kentucky bluegrass 1.5 to 2.5, 2 to 3.5 and 1.5 to 2.5; perennial ryegrass 1.5 to 2.5, 2.5 to 3.5 and 1.5 to 2. Use the summer height in shade. Remove no more than a third of the blade, and look for white grubs in brown areas in July; treat at 5 to 10 per square foot.

Fall

Seed cool-season grasses between August 25 and October 10, and prepare the seedbed in August. MU says seeding in late summer is preferred because temperatures favor seedlings, and that fall seedings are much more successful than spring ones. If you plan a full renovation, kill the old vegetation with glyphosate about mid-August.

September is the most important feeding, at 1 to 1.5 pounds of nitrogen per 1,000 square feet with a balanced fertilizer. If you want only one feeding, make it September; a second in mid-October is a good choice, and moderate rates in October or November, after daytime temperatures fall to about 50 F, extend green color and root growth. Late September is the best time for broadleaf herbicides, especially perennial broadleaf weeds.

Nitrogen by grass and the bag math

MU's annual totals: common Kentucky bluegrass 2 to 3 pounds of nitrogen, higher-quality bluegrass 4 to 5, red fescues 2, bluegrass with red fescue 2 to 3, and tall fescue or ryegrass 3 to 4. Each application is about 1 pound per 1,000 square feet, with April cut to 0.5 to 0.75 pound.

To turn 1 pound of nitrogen into product, divide 100 by the nitrogen percentage on the bag: a 20 percent fertilizer takes 5 pounds per 1,000 square feet. The lawn fertilizer calculator on this site does the division and multiplies by your lawn size.