How to Make the Grass Greener on Your Side : ‘Renovation’ is often answer to a lawn that’s full of weeds or shows only brown stubble.

Fall-planted flowers are coming into full bloom, deciduous trees are leafing out, shrubs are flowering and the garden is beginning to look its best. Except for the lawn.

The annual rye you tossed on top in the fall is fading fast and all that’s left are weeds--dandelions, clover, coarse grasses. The Bermuda or the Kikuyu--Southern California’s two most common grasses--are present but struggling.

Or, perhaps this better describes your lawn: You have a stand of Bermuda or Kikuyu so thick that it is like a mattress, but every time it is mowed, all that’s left is brown stubble.

One or the other of these descriptions probably fits most of the lawns in Southern California, and both types of lawns beg for “renovation.”

Specializes in Lawns

Renovation generally means to renew or revitalize an existing lawn, but it can also mean replacing it entirely. To sort this all out, I asked Bob Cohen, what he would do for these two common lawns that are faring poorly.

Cohen is a former engineer who has turned his attention to lawns, and now runs Green Scene in Tarzana, a specialized lawn-care company. Some of his suggestions run contrary to popular opinion and practice, but are backed up by a lot of firsthand experience, caring for a lot of lawns (5,000 lawns in 20 years).

He says that first you must know what is growing out there--what your lawn is made up of. Bermuda and Kikuyu grasses are the most common, so at home in Southern California that Cohen calls them “indigenous.”

They are warm-season grasses--they grow during warm weather--and they are spreading grasses, sending out runners in all directions. In winter, they may go completely dormant, and that is where the practice of “over-seeding” them with an annual winter grass, usually annual rye, comes from. The annual rye covers the dormant grass from November through March.

‘Low and Close’

Bermuda and Kikuyu grasses should grow “low and close,” according to Cohen, but in time they grow too tall, so every time they are mowed, only the brown base remains.

Renovation for a thick cushiony lawn like this is straightforward if you have the right equipment.

A machine called a vertical mower, or “dethatcher,” rips out mounds of tall growth and gives the lawn a fresh start. Make no mistake, this is a big job, and Cohen figures it will cost $200 to $500 per each 1,000 square feet of lawn to have someone else do it. The job includes a good fertilizing and chemical conditioning of the soil (including the use of a wetting agent to help water soak in), plus the addition of an herbicide to keep crab grass from invading this renewed turf.

In two to three weeks the lawn fully recovers and is low, lush and green again and should be mowed from then on at a height of 1 inch for Bermuda or three-quarter inch for Kikuyu. The time to renovate a lawn this way is from late February into June.

Sun and Warmth Needed

This kind of renovation may also be the ticket for the lawn that is struggling along full of weeds and dead spots, but sometimes this is an indication that conditions do not suit the common Bermuda or Kikuyu, both of which need lots of sun and warmth. Perhaps trees have grown and are shading more of the lawn.

In this case, “renovation” may mean “replacement.” Cohen suggest that first you try to get the existing grass to grow this spring and summer with proper watering and fertilization plus weed control, and perhaps dethatching,

By late summer, if things have not improved, consider replacing these grasses with another perennial grass, most likely one of the modern, turf-type tall fescues that are doing so well in Southern California. (Green Scene maintains test plots of 13 varieties of grasses; they can be seen at 5842 Tampa Ave., Tarzana.)

This costs, ballpark for 1,000 square feet, about $30 to kill off the existing grass, $150 to $300 for a vertical mowing that rips most of it out (so the seed can come in contact with the soil), and then around $100 for the new seeding, fertilizing, weed control and soil conditioning.

Tilling and Sodding

This work should be done in late summer or fall, when the warm-season grasses are actively growing so the herbicide (Roundup or Kleenup) can work and so the new lawn has the cooling days of fall and winter to look forward to.

You can also get more deluxe, by having the soil tilled at this time and sod installed for a total cost of around $1,000 for 1,000 square feet.

Interestingly, Cohen seldom sees need for the addition of organic soil amendments (though he does add chemicals to loosen clay soils), or aeration--the removal of plugs of soil to let water and air penetrate.

He thinks most Southern California soils are just fine if properly watered and fertilized, though he says there are pockets of sandy soil that require the addition of organic matter (he favors peat moss).

Soaking in Deep

Improper watering is the chief villain, Cohen believes, not clay soils, and his recommendations on watering are going to surprise a few people:

He thinks most lawns rarely require watering more than once a week near the coast, twice a week in the inland valleys; less in spring and fall. This goes for Bermuda, Kikuyu and the tall fescues (bluegrass is another story and is not recommended for Southern California).

However, the water must soak in to at least 6 inches, so this means watering for 20 minutes or more. (If you want to figure out how deep the water is getting, 1 inch of water soaks 6 inches deep in most soils. See how long it takes your sprinklers to fill a cup with 1 inch of water--that’s how long to water each time.)

If the water runs off the lawn, water in short bursts instead. This is easily done with automatic systems. Water for five minutes, turn it off, then on for another five, 15 minutes later, and so on, until the water has soaked deep into the soil, with little or no runoff. Then don’t water for a week.

If it gets really hot one afternoon, turn on the sprinklers for a minute to cool the grass off, but this doesn’t count as an irrigation.

To further help the water soak in, Green Scene uses wetting agents such as Water-In.

In fact, if neither of the descriptions above fits your lawn, suspect too frequent watering--you may be drowning your lawn, killing off beneficial bacteria and starving the roots for air. Because of the drought, this is the perfect year to try watering less often. Just make sure it soaks in.