Killing Weeds in Bermuda Grass
Perhaps the biggest problem with weeds in bermuda grass occurs during the cool winter months when bermuda grass becomes dormant. Grassy and broadleaf weeds can invade quickly and spot the otherwise sandy-smooth look of dormant bermuda grass as seen by the invasion of annual bluegrass shown below.
One proactive measure is to put down a layer of pre-emergent like Halts® as soon as it begins to turn cool in the fall and again when it begins to warm in late winter. However, our experience has been that this is simply a limiting measure and not foolproof by any means. Particularly in late winter it is hard to predict the warming cycle and a pre-emergent may need to be applied twice.
Fortunately, a number of weeds can be killed with a granular or liquid application of weed killer and the sooner you apply a weed killer to your lawn the better. Young weeds are typically easier to kill and getting them early reduces the chances that they will spread. If necessary, mow your lawn and bag the clippings to keep some types of weeds like annual bluegrass from going to seed.
Some grassy weeds are very hard to kill and can be more like a human disease - manageable but sometimes impossible to cure. Our personal "most hated weed" is annual bluegrass which rarely responds to off-the-shelf herbicides and is best managed by proper lawn care techniques. However, our bermuda grass lawn restoration project recently exposed one herbicide as a candidate for annual bluegrass control.
Young annual bluegrass is shown in the image to the right. It is a deep green color and grows in a spherical clump from a central root ball. It spreads by seed so it is important to regularly mow and bag your clippings if invaded by this weed to minimize the number of seeds that will lay dormant in your bermuda grass all summer long until the fall when they begin to germinate.
Small nuisance areas can be addressed by pulling the weed by hand when the soil is moist. This can be a great job for kids.
However, annual bluegrass often thrives in part because the soil in your bermuda grass lawn may be compacted. This can be an even bigger problem for lawns with a clay-type soil like the infamous Georgia red clay. So be sure to implement a regular aeration routine to your lawn if annual bluegrass is a problem. Core aeration is usually best in this instance.
Another factor in the growth and spread of annual bluegrass is the thickness of the bermuda grass in your lawn. And if your soil is compacted then it is quite possible that your bermuda grass is not doing its best. We suggest you consider following our Bermuda Grass Lawn Calendar for recommended lawn care tasks throughout the year to help improve the health of your bermuda grass.
The good news is that annual bluegrass does not like heat or drought so as soon as your days are hot and your nights are warm you will see this pesty weed grass disappear until cooler days return. During the heat of the summer, when bermuda grass is at its peak growing time, you can focus on making your bermuda grass thicker and healthier to help choke out the annual bluegrass next season.
Bittercress (Hairy, Wavy)
Bittercress is an interesting weed with two very different looks depending on the phase of maturity. At the ground level this weed appears like a dense, low-growing clump of small, roundish leaves that begin to turn yellow as the plant matures or daytime temperatures rise.
As bittercress grows it sends up spindly, straight stalks that can exceed ten or twelve inches if left unchecked. It is on these stalks that thin long seeds pods of an inch or more grow. When mature, these pods will explode sending their seeds several feet away (or even further on a windy day. If you happen to brush against a bittercress plant while wearing shorts it is possible to feel the seeds hit your legs as the pod explodes.
Bittercress can be controlled with a liquid spray post-emergent herbicide from companies like Spectracide, Ortho, or Bayer. However, if bittercress has already gone to seed in your lawn you should plan to put down a pre-emergent in the fall and spring, keep your lawn cut so that new seeds pods cannot develop, and use a post-emergent herbicide early next season.
Mouseear chickweed forms a dense mat at ground level as it grows outwards and eventually sends up long, purple stalks with white flowers. The leaves are a medium-green with a hairy surface that is particularly apparent in the morning dew.
This weed can spread quickly in short lawn grass grasses because the thick, dense leaves block out sun.
Fortunately, mouseear chickweed can be controlled by many common herbicides that can be found at big box retailers and small family stores alike.
In our informal April 2010 weed test, spray herbicides from both Ortho and Spectracide performed similarly and did a good job killing off the mouseear chickweed. When selecting an herbicide be sure to read the label for specific weeds controlled and follow the manufacturers directions for application.
Expect that your mouseear chickweed will take four to six weeks to completely disapper from your lawn after application of herbicide but our test lawn did not require a second application.
If your mouseear chickweed is flowering then there is a chance it is going to seed. Keep a close watch for reappearance in fall or spring. A pre-emergent can help reduce the amount of this weed that re-emerges the next growing cycle.