Lawn care calendar for Louisiana: when to fertilize and seed

LSU gives the rates and the September rule; the monthly spacing between April and August is our reading, because its calendar chart marks mowing and watering across the whole growing season rather than dated feedings.

Which grasses grow where in Louisiana

The LSU AgCenter calls centipedegrass and St. Augustinegrass the most common lawn grasses in the state. All warm-season grasses can grow here. St. Augustine has the coarsest texture and moderate to high upkeep, and some varieties struggle with chinch bugs and a decline virus. Centipede is medium-textured, needs less maintenance and a lot of water in dry spells, and can slide into decline syndrome if it is overfed.

Bermudagrass wants full sun, high fertility and a reel mower if it is cut below 1 inch. Zoysia makes the best-looking lawns but grows slowly and builds thatch. LSU notes that severe cold in north Louisiana often injures or kills the less hardy grasses, among them St. Augustine and carpetgrass, and says low nitrogen and high potassium in late summer strengthens their cold tolerance.

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 Shreveport the last spring frost averages March 9 and the first fall frost November 18. At Lafayette Regional Airport the dates are February 13 and December 4. At New Orleans (Audubon) they are January 24 and January 2, so in half of all years New Orleans does not freeze until after New Year.

Counting the days between them, Shreveport has about 254 frost-free days and Lafayette about 294 (our arithmetic). LSU says north and south Louisiana differ by two to four weeks in when jobs start and end. Lafayette's average last freeze comes 24 days before Shreveport's and its first comes 16 days after (our arithmetic).

Spring and early summer

Crabgrass seed germinates when the soil warms to 55 to 60 F, which LSU places in mid to late February around Baton Rouge and early March around Shreveport and Monroe. That sets the preventer date. Healthy turf crowds out crabgrass, and the guidance stresses that thin lawns let light reach the seed.

LSU says to plant warm-season sod, sprigs or seed when the soil warms to about 70 F at 2 inches deep, and to have the soil tested at least a month before planting. St. Augustine is planted as sod or plugs, since it is not grown from seed, while common centipede can be seeded on sandy soil that will not crust.

Summer

Mid summer is the time to grow and thicken the lawn. St. Augustine takes three to four applications of 1 pound of nitrogen per 1,000 square feet a season and centipede half as much, and LSU warns that missing this difference can lead to centipede decline syndrome. A general fertilizer with a 3-1-2 or 4-1-3 ratio fits the average soil; a 9-1-1 product works if you add potash in early fall.

LSU says the old one inch a week rule means little, because clay holds up to two and a half times as much water as sand. Water when the first dry or off-color patches show, enough to wet about 4 inches, then check with a shovel. Mow St. Augustine at 2.5 inches in sun and 3 in shade, centipede at 1 to 1.5 inches, and sharpen the mower blade twice in a season.

Fall

In September the emphasis changes from growth to strength. LSU says to use a fertilizer with less nitrogen and more potash, or muriate of potash at 1 to 2 pounds per 1,000 square feet if you fed mostly nitrogen all summer, and to apply any fall feeding in September because it is not needed later. Northern-blend winterizers that are high in nitrogen are the ones to avoid.

Keep fallen leaves off the turf, water if the season is dry, and raise the cutting height a notch except on centipede. You do not need to aerate or dethatch in fall. LSU puts weed control in the cooler fall, late winter and spring so it does not stress the lawn.

Fertilizer rules

The Louisiana Department of Agriculture and Forestry runs a fertilizer program that covers registration, labeling and tonnage reporting. I found no state rule that limits phosphorus in home lawn fertilizer. The practical limit is on the bag: LSU recommends a 3-1-2 or 4-1-3 ratio, which has little phosphorus, and a soil test every few years.

The calendar needs one more input: the pounds of nitrogen in a bag. The lawn fertilizer calculator on this site converts the first number on the label into pounds of product for your lawn.