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Quick answer
Mow bermuda low, to about 1 to 1.5 inches, just before you overseed, so the ryegrass seed reaches the soil. Make the first cut on the ryegrass when it’s about 30% taller than your target, roughly 2.75 to 3 inches. Keep it at 2 to 3 inches through winter with a rotary mower. In spring, lower the mowing height and mow more often. That stresses the ryegrass as the weather warms, and lets the bermuda take back over once soil and night temperatures approach 65°F.
Overseeding bermuda with ryegrass keeps a southern lawn green while the bermuda sleeps brown through winter. It’s common from Arizona to Georgia. It also turns mowing into a three-season job with different heights at each stage, and getting the spring stage wrong can leave you with thin, patchy bermuda in June.
This guide follows the mowing from seeding day to summer, using advice from the University of Arizona, the University of Georgia and Georgia garden expert Walter Reeves. MowReview quotes no prices and hasn’t tested the products mentioned. How we research explains why.
Should you overseed at all?
Walter Reeves says to overseed “ONLY IF your bermudagrass is in very good shape,” because ryegrass competes with bermuda for moisture, sunlight and nutrients, and “may retard the warm-season grass unless managed correctly in the spring.” A thin bermuda lawn is better left dormant and fed properly next summer.
The mowing heights, stage by stage
| Stage | Mowing height or trigger | Source |
|---|---|---|
| Just before seeding | Bermuda at 1 to 1.5 in, or lowered 25 to 30% more and clippings left | Walter Reeves; University of Arizona |
| First cut on the ryegrass | When rye reaches 2.75 to 3 in, or 30% above the target height | University of Arizona; University of Georgia |
| Winter, rotary mower | 2.25 to 2.75 in (Arizona); 2 to 3 in (Reeves) | University of Arizona; Walter Reeves |
| Winter, reel mower | 1 to 1.5 in on higher-quality turf | University of Arizona |
| Spring transition | Lower the height by 35% and mow more often; or mow to 1 in a few weeks before the last frost | University of Arizona; Walter Reeves |
Before seeding: get the seed to the soil
Timing comes first. The University of Arizona says “October is ideal for overseeding when daytime air temperatures are 80-85°F and nighttimes are about 55°F.” Seed too early and the still-growing bermuda crowds out the rye; too late and frost can hit the seedlings. In Georgia, Walter Reeves suggests about 30 days before the first frost.
Then lower the bermuda so seed can reach soil. Reeves says to mow it to “one to one and one half inches high.” The University of Arizona has a more gradual plan: raise the height 30 to 40% two weeks ahead, mow at the old height a day or so before, then lower it another 25 to 30% just before seeding, leaving the clippings as mulch.
The first cut
The University of Georgia’s advice, from turf specialist Clint Waltz, is to “begin mowing when seedling height is 30% higher than desired.” The University of Arizona puts it at 2.75 to 3 inches. Both say to mow only when the grass is dry, with sharp blades.
Use a rotary mower for the first cut, even if you’ll use a reel later. Georgia’s advice is that a rotary cuts seedlings cleanly rather than tearing them, and to switch to a reel mower only after the second or third mowing.
Winter: keep it at 2 to 3 inches
Through winter, mow the ryegrass at 2.25 to 2.75 inches with a rotary mower, as the University of Arizona advises, or 2 to 3 inches by Reeves’s guide. The University of Georgia stresses that the height should stop the overseeded grass from shading out the bermuda underneath.
Fertilizer timing matters too. Georgia’s guidance is to fertilize after the seedlings emerge, generally three weeks after seeding, and Reeves suggests feeding the rye again in early February. He warns that fertilizing the rye can make the bermuda more vulnerable to cold injury in a severe winter.
Spring: mow the rye out
This is the stage most people get wrong. Ryegrass loves cool spring weather and will happily hang on into May, shading the bermuda just as it tries to wake up. Mowing is your main tool for tipping the balance back.
- Lower the height. The University of Arizona says to lower it by 35% and mow more often. Reeves suggests mowing the rye and bermuda down to 1 inch a few weeks before the last spring frost.
- Watch the temperature. Georgia’s guidance says warm-season grass resumes growth when soil and night temperatures approach 65°F.
- Time the fertilizer. Reeves says to wait until the bermuda is at least 50% green, usually in early May, before feeding it.
- Keep watering. The University of Arizona says drying the lawn out can slow bermuda’s recovery.
- Finish the job. When about 80% of the lawn is bermuda, Arizona suggests a light verticut to remove the remaining ryegrass.
Then return to your normal summer bermuda height. Robot mowers for bermuda covers summer heights and which robots can cut that low.
The picks
Seed made for overseeding bermuda
Pennington Fairway Supreme Perennial Ryegrass
- Stated rate10 lb per 1,000 sq ft
- Germination7 to 21 days
- LightFull sun to light shade
Pennington describes it as “ideal for fall overseeding of Bermudagrass,” for temporary winter color on dormant southern lawns. It’s a perennial ryegrass, the type the University of Arizona’s seeding rate is written for.
Good for
- Healthy bermuda lawns in full sun
- Owners who want a finer-textured winter lawn
Less good for
- Shady lawns: Pennington says it isn’t ideally suited to heavily shaded areas
- Easy spring removal: Reeves warns heavier seeding makes rye harder to remove the next summer
- Reading coverage off the bag: Pennington’s listed coverage and seeding rate don’t fully match, so measure your lawn
For even seeding and feeding
Scotts Elite Spreader
- TypeBroadcast (rotary) spreader
- HopperUp to 20,000 sq ft of product
- Edge controlEdgeGuard
Ryegrass seeding rates are heavy, and the University of Arizona recommends spreading in two passes at right angles for even cover. A large hopper and a 6-foot spread pattern make that quicker, and EdgeGuard keeps seed and fertilizer off the driveway.
Good for
- Midsize to large lawns
- Seeding in fall and fertilizing through winter and spring
Less good for
- Small yards: Scotts positions it for very large lawns
- Long-term repairs: Scotts’ FAQ says it has no mechanical warranty, relying on a one-year refund guarantee instead
For a lower winter cut, after the first mows
Fiskars StaySharp Max reel mower
- Cut width18 in
- Height1 to 4 in
- PowerManual
A reel mower is what the University of Arizona’s lower winter height of 1 to 1.5 inches is written for. Bob Vila gave the StaySharp Max 9.2 out of 10, and found it handled typical lawns easily, even with twigs and weeds that stalled older reel mowers.
Good for
- Small to midsize overseeded lawns mowed regularly
- Owners who want a quiet, fuel-free winter mower
Less good for
- The first cuts on new rye: Georgia’s advice is a rotary first, then a reel after the second or third mowing
- Dense grass at low heights: Bob Vila says it may struggle to keep dense lawns low
- Overgrown grass: the reviewer had to raise the reel and mow twice where grass had fallen over
Questions
How high should I mow ryegrass overseeded on bermuda?
About 2 to 3 inches with a rotary mower. University of Arizona Cooperative Extension gives 2.25 to 2.75 inches with a rotary mower, or 1 to 1.5 inches with a reel mower on higher-quality turf. Georgia garden expert Walter Reeves says 2 to 3 inches through winter.
When should I first mow newly seeded ryegrass?
When it’s about 30% taller than your target height. University of Georgia advice is to begin mowing when seedlings are 30% higher than desired, and the University of Arizona says to mow when ryegrass reaches 2.75 to 3 inches. Mow when the grass is dry, with a sharp blade.
Should I scalp bermuda before overseeding with ryegrass?
Lower it, so the seed reaches the soil. Walter Reeves suggests mowing bermuda to 1 to 1.5 inches before seeding. The University of Arizona suggests lowering the height by another 25 to 30% just before seeding and leaving the clippings.
How do I get rid of ryegrass in spring so bermuda comes back?
Mow lower and let the heat do the work. The University of Arizona says to lower the mowing height by 35% and mow more often in spring. Walter Reeves suggests mowing the rye and bermuda to 1 inch a few weeks before the last spring frost.
When does bermuda start growing again in spring?
University of Georgia guidance says warm-season grass resumes growth when soil and night temperatures approach 65°F. That’s when the ryegrass starts to decline and bermuda takes over.
Does overseeding with ryegrass hurt bermuda?
It can, if it isn’t managed in spring. Walter Reeves warns that overseeding may slow the warm-season grass, and that ryegrass competes with bermuda for moisture, sunlight and nutrients. He says to overseed only if the bermuda is in very good shape.
The short version
Mow the bermuda low before seeding, make the first cut on the rye when it’s about 30% over your target, and keep it at 2 to 3 inches all winter. In spring, mow lower and more often as the weather warms, wait for the bermuda to green up before feeding it, and let the heat finish off the rye.
Bermuda lawn?
See which robot mowers cut low enough for bermuda in summer.
