Good soil-to-seed contact key to overseeding

Q: My backyard has a Bermuda grass lawn and I would like to overseed with a winter ryegrass seed. When I have done this before, I "burned out" the Bermuda by not watering it, then rented a power rake to dethatch it. This year with all the rain, my Bermuda is not turning brown. My concern is if the lawn is green, then the power rake will not remove the thatch. Also, which do you recommend: annual or perennial rye seed and why?

A: Overseeding Bermuda grass with a cool-season grass such as one of the ryegrasses has a window of time that is optimum in the fall. This window is from Sept. 15 to Oct. 15. If you overseed too early, the Bermuda grass is too active and will compete with your winter lawn. If you overseed too late, you run the risk that it will get too cold quickly and the overseeded grass may not all germinate and fill in your overseeded area.

The mantra for effective overseeding is having "good soil-to-seed contact." In other words, the seed should rest on the soil when you overseed correctly. If the Bermuda grass is too dense, much of the seed will not land on the soil and you will have a spotty winter lawn.

Sounds as if you have the correct sequence for overseeding. Time the overseed for around Oct. 1. On Sept. 15 turn off the water to the Bermuda grass. On Sept. 21 mow as short as possible , then power rake or dethatch until you see bare soil, apply seed, fertilizer, topdress the seed, fertilizer and water.

Bermuda grass lawns are usually mowed somewhere from ½ to 1 inch high. I like to let it grow to 1½ inches in August/September. This produces more stem so I can "scalp" it better and get the seed to fall onto the soil for that good soil-to-seed contact.

You can use annual ryegrass if you want, but it is coarse textured, light green and rough to the touch. Perennial ryegrass is a much prettier grass and softer to the touch. You can put all the nitrogen you want on annual ryegrass and it will just not get the same dark green color as perennial ryegrass. It is more expensive but will give you a much prettier lawn.

Q: I found this vine growing in my lawn and sent you pictures of it. I tried treating it with Ortho's Weed Be Gone. I still have the vine. Do you have any idea what it may be and how I can treat it or get rid of it?

A: From the look of this "vine," it appears to be Bermuda grass. Some old-timers call it devil grass, mostly because it is the devil to get rid of. Once it is in a lawn, it is tough to nearly impossible to get rid of.

It is easier to get rid of if it is in a shrub bed. Then you can cut it back to a foot long (as long as it has leaves) and "spot spray" what's left with Roundup. Other products that have reasonable success at some control include Poast and Fusilade, which can be used fairly safely among shrubs and ground covers.

Bermuda grass usually gets in a lawn if the lawn begins to thin or lose its density , which can be caused by not fertilizing regularly, mowing too short or an insect or disease problem.

Mowing too short can occur by lowering your mower too close to the ground or by using a line trimmer and whacking the grass low around sprinkler heads or along the edge of the lawn to make it look pretty.

The best defense is a good offense. Keep the lawn at 2 to 2½ inches if it is fescue. Keep it fertilized regularly. If patches of the lawn die, do not disturb the dead area and/or reseed or resod until mid-to-late September when Bermuda grass is going to sleep.

Bob Morris is a horticulture expert living in Las Vegas; he is on special assignment in the Balkh Province, Afghanistan, for the University of California, Davis. Visit his blog at xtremehorticulture.blogspot.com.