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.