Lawn care calendar for South Carolina: when to fertilize and seed

Clemson publishes the same calendar for the whole state and tells you to adjust for the year and the region; green-up is mid-April on the coast and as late as mid-May inland.

Which grasses grow where in South Carolina

Clemson publishes yearly programs for bermudagrass, centipedegrass, zoysiagrass, St. Augustinegrass and tall fescue. Bermudagrass wants full sun and a mowing height of 1 to 2 inches. Centipedegrass is the low-input choice at 1 to 2 inches, or 2 inches in partial shade, and gets half the nitrogen of the others. Zoysiagrass is cut at 1 to 2.5 inches, with 1.5 inches typical, and St. Augustinegrass at 2.5 to 4 inches, with 3 to 4 inches in shade.

St. Augustinegrass is the least cold tolerant of the group, which is why it dominates the coast. Tall fescue, the one cool-season grass on the list, runs on a different calendar, with feeding in September, November and February.

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 Columbia the last spring frost averages March 25 and the first fall frost November 7. At Charleston International Airport the dates are March 7 and November 27. At Greer, which serves Greenville-Spartanburg, they are March 28 and November 7.

Counting the days between them, Charleston has about 265 frost-free days against 227 at Columbia and 224 at Greer (our arithmetic). Clemson puts green-up in April on the coast and as late as mid-May inland, and warns that bermudagrass and centipede can green up and get burned back by frost more than once before settling.

Spring

Weed control starts first. Clemson says to apply pre-emergent herbicide in mid-February in coastal and central areas and mid-March in the Piedmont and mountains, with a second application 8 to 10 weeks later. Do not spray post-emergent weed killer during green-up; wait until the grass is fully green.

Lower the mower to about 1 inch for bermudagrass and centipede just before green-up, then wait for full color before feeding. Early May is when Clemson starts nitrogen at 1/2 to 1 pound per 1,000 square feet, with the rate depending on soil. Core aeration comes after the threat of frost has passed. If a pre-emergent is already down, Clemson says to hold off until just before the next application, because disturbing the soil breaks the barrier. May is also the month Clemson picks for replanting bare areas with sod, plugs or sprigs, and for seeding centipede at 1/4 to 1/2 pound per 1,000 square feet.

Summer

Bermudagrass, zoysiagrass and St. Augustinegrass lawns total 2 to 4 pounds of nitrogen a season, the higher figure on sand and the lower on clay. Centipedegrass takes 1 to 2 pounds. Bermudagrass gets a mid-summer feeding in June or July with a potassium-rich fertilizer such as 15-0-15. Clemson sets the last warm-season feeding before August 15, and for centipede the cutoff is August 15 in the Upstate and September 1 on the coast.

Clemson says to water when the whole lawn looks dry, with 3/4 to 1 inch the next morning, and to wait for stress before watering again. Tall fescue gets no feeding and no herbicide from June through August, and its mower is raised to 3.5 inches.

Fall and winter

No nitrogen goes on warm-season lawns from September on, and the mower stays at its normal height until nights drop below 70 F, when Clemson tells you to raise it slightly. September is the month for a pre-emergent against winter annual weeds, with a second pass 8 to 10 weeks later. Overseeding is for bermudagrass only; Clemson says the extra water, feed and shade will damage centipede, zoysia and St. Augustine.

Ryegrass overseeding is timed about 30 days before the first frost, when daytime highs are near 70 F and nights stay above 50 F. Clemson gives 5 pounds of seed per 1,000 square feet over an established lawn and 10 pounds on bare ground, and mows ryegrass at 1.5 to 2 inches. Tall fescue is the other fall seeding: a blend at 6 pounds per 1,000 square feet in September and early October with a high-phosphorus starter fertilizer.

Fertilizer rules and soil tests

South Carolina fertilizer law is Title 46, Chapter 25 of the state code, which covers registration, labeling and the grade of fertilizer, and defines specialty fertilizer as the kind sold for home lawns and gardens. The chapter I opened contains no limit on phosphorus in lawn fertilizer. Clemson sets the rule in practice: established centipede lawns should get phosphorus only if a soil test shows a deficiency, and the other warm-season calendars leave phosphorus to the soil test as well.

Clemson says to base lime, sulfur and fertilizer on a soil test, and county Extension offices take the samples. Bermudagrass wants a pH of 6 to 6.5 and centipede 5.5 to 6.

The bag math

Clemson gives a shortcut: divide 100 by the first number on the bag to get pounds of product for 1 pound of nitrogen per 1,000 square feet, or 50 for half a pound. The lawn fertilizer calculator on this site does the same for your lawn size and any bag, including split slow-release blends.