How to Overseed With Annual Ryegrass

Warm-season grasses thrive in temperatures between 80 and 95 degrees Fahrenheit and are typically green in the summer and lose color in winter. Annual ryegrass (Lolium multiflorum), a cool-season grass that thrives at 65 to 75 F, is seeded on top of warm-season grass, a practice called overseeding, to make it green in winter.

Most over-seeding with annual ryegrass is done on Bermuda grass (Cynodon dactylon, which grows in U.S. Department of Agriculture plant hardiness zones 6a through 9b. You can overseed St. Augustine grass (Stenotaphrum secundatum, USDA zones 7a through 11) and centipedegrass (Ermochloa ophiuroides, USDA zones 7a through 11) but they are overloaded by the winter fertilizer needed for the annual ryegrass. Japanese zoysia (Zoysia japonica, USDA 7a through 11) and other zosia grass species are so thick that annual ryegrass seeds have difficulty germinating and growing.

Over-seed when late summer or early fall daytime temperature drops to 70 to 75 F and soil temperatures are between 50 and 65 F, roughly two weeks before the first fall freeze.

Remove excess thatch of the perennial grass so the annual ryegrass seeds can reach the soil. You can remove thatch with a garden rake that has hard tines or rent a power thatcher to get the job done. Some mowers have attachments that remove thatch.

After removing thatch, mow the lawn as low as you can without scalping it, the term for cutting grass so low as to cut the stems. Collect the clippings or rake them up.

Sow 5 to 10 pounds of annual ryegrass seed per 1,000 square feet over Bermuda grass and no more than 3 pounds of seed over St. Augustine grass. Use ryegrass seed treated with fungicide to lower the chance of disease.

Mechanical spreaders scatter seeds better than doing it by hand. Sow the seeds in two passes with the second pass a right angle to the first. Refer to the seed bag as well as your spreader to correctly calibrate the rate.

Drop spreaders spread seeds in a 22- to 42-inch-wide swaths with calibrations set for a walking speed of 5 feet per second.

Rotary spreaders apply grass seeds less evenly. To calibrate a rotary spreader, use the manufacturer’s suggested application rate to scatter annual ryegrass seeds over a plastic drop cloth at a 5 miles per hour walking speed. Collect and weigh the seeds. Using the weight of seeds on the drop cloth as a guide, readjust the application rate to get the correct rate.

After you sow the seeds, pull the back of a rake, an old piece of carpet or a section of chain-link fence over the area in at least two directions to knock the seed through the base grass.

Water twice a day to keep the soil moist for the first three to five days, the usual time it takes for the seeds to germinate. Water only enough to moisten the seeds. Reach through the perennial grass with your fingers to ensure the ryegrass seeds are moist. Don’t overwater. Flooding the lawn will encourage disease or wash the seeds away.

After the seeds germinate, water the soil once a day for a week then two or three times a week. Use your fingers to check that the soil is moist as deep as the developing roots. Reduce or eliminate watering if it has rained.

When you see the annual ryegrass growing through Bermuda grass, apply 1/2 pound of 5-10-10 or 10-20-20 slow-release fertilizer per 1,000 square feet. Water it in. Use one-half of this rate if you are overseeding St. Augustine grass.

Fertilize with 1/2 pound of 12-4-8 or 16-4-8 slow-release fertilizer for each 1,000 square feet in November and February. If you’re overseeding St. Augustine grass that has been damaged when it was dormant in the past, do not fertilize the overseeded lawn.

Annual ryegrass will grow from 4 to 5 inches tall in three weeks. Use a mower with a sharp blade to mow it 2 to 4 inches high. Dull blades can rip the seedlings from the ground. Only mow over-seeded annual ryegrass when it is dry and never mow more than one-third of the blades at once.