How to Kill Bermuda Grass

In its proper place, Bermuda grass (Cynodon dactylon) makes a good lawn or good pasture. Unfortunately it doesn't stay in its proper place. The underground roots and the above ground runners spread everywhere. Soon you have Bermuda grass erupting from your flower beds, creeping through your cactus, tangling in your shrubs and even invading your garden shed. Killing Bermuda grass is not difficult, but it's not going to happen overnight.

I'm a desert landscaper. I spend a lot of time killing lawns, especially Bermuda grass lawns, to replace them groundcovers that use less water. I have learned that no matter what the herbicide package says, it will take at least a month and several applications of herbicide to kill 90 to 95% of the Bermuda grass, then several months of spot application on surviving sprigs to get the remainder. It's a tough plant. It's so tough that it grows in the cracks of the concrete medians in the middle of a Phoenix freeway.

The most frequent mistake people make when they try to kill Bermuda grass is to yank out, mow down, or clip off as much visible growth as possible, then use an herbicide "to finish the job". Herbicides must be absorbed by the leaves to be effective. If you remove most of the leaves before you apply the herbicide, very little of the herbicide will be absorbed. The grass will regrow from the roots.

The second most common mistake is to try to kill the Bermuda grass by withholding water, then resorting to herbicides when the grass refuses to die. This is a native of the African savannas, where 6 months without rain is normal. You aren't going to kill it by shutting off the sprinkler for a few weeks. Bermuda grass can survive herbicides better when it is water-deprived because it absorbs less herbicide when it is dormant from drought.

A third mistake is trying to kill Bermuda grass during cool weather. The days and nights must be warm enough that the Bermuda grass is actively growing. Let it "green up", and don't start killing the lawn unless you have at least 6 weeks of warm weather left.

How to Kill Bermuda Grass
When the grass is green and actively growing, follow these steps:

1. Water the Bermuda grass thoroughly to encourage it to grow. Herbicides work best when the plants are actively growing.
   
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3. Wait a week, water the Bermuda grass in the morning.
   
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5. The following morning, thoroughly spray the Bermuda grass with an herbicide that contains glyphosate. Make sure you follow the package directions for diluting the herbicide. Spray the grass thoroughly, making sure you cover all the leaves.
   
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7. Wait at least three days to give the herbicide time to be absorbed and spread through the plant tissues.
   
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9. Now you can yank, clip and mow, because the herbicide has spread into the roots.
   
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11. Keep watering deeply every few days, as if you were trying to grow the best lawn on the block.
    
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13. Give the survivors a week or so to grow some leaves, then spray them with the herbicide again.
    
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15. Repeat the cycle of water, herbicide, water, herbicide until the sprouts stop appearing.
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17. Patrol the area for the next two or three growing seasons and apply herbicide to any new sprouts. The roots of Bermuda grass can be as deep as six feet, and they persist for several years.
    
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About Glyphosate
Glyphosate kills plants by shutting down an important metabolic pathway. Insects, birds, and animals do not have that pathway, so glyphosate is safer to use than some herbicides. However, follow the precautions in the instructions for diluting, applying and cleaning spray equipment.

Glyphosate was first introduced by Monsanto as Roundup® but the patent has expired and it is available from various manufacturers. Regardless of the brand you purchase, the active ingredient for all glyphosate products is exactly the same. For the most cost-effective herbicide, look for a brand with the highest concentration of glyphosate, then dilute it according to the package directions.

CAUTION: Glyphosate kills almost all plants, and even a small amount of spray will retard their growth. Do not spray herbicides on breezy days. Protect the plants you do not want to kill with a shield. I slide paper bags over small plants and drop a box or trashcan over larger ones, spray the neighboring weeds, then remove the shield.