By Maureen Gilmer
While a student in the 1970s, I was faced with caring for a project where black plastic was laid over an old lawn and the whole thing covered with bark as a low-maintenance, water-conserving yard alternative.
By the time I came onto the scene, the running grasses were traveling up to 10 feet in the dark under that plastic as they sought light at its edges. The few creeping junipers that were planted through the plastic became nests of runner grasses after the first growing season. It was irreparable. The whole project had to be thrown out so the old lawn could be removed properly to prevent such rapid reinfestation of aggressive running grasses.
For projects where the lawn is removed in favor of more water-conserving surfacing, the removal of running grasses becomes very important. Failure to get them out means that such pernicious plants will inevitably rise again to infest your new surface. To avoid this, it’s vital to remove grass properly so it won’t come back.
Out west and in the South, Bermuda grass is a good example because it grows virtually everywhere and travels almost as fast as I can walk. This grass and its kin demonstrate the characteristics of other running-grass species as well.
Bermuda is composed largely of thick, ropy runners that are very hard to break. This is key to its spread and establishment. Each original plant is composed of a bundle of deeper feeder roots. From the root crown at the surface extend traveling stems. Stolons grow on top of the ground and rhizomes underground. Both of these are segmented by regularly spaced growth nodes, with each able to produce roots, shoots or both.
A single stem may be over a foot long, with many rooting points along its length. Try to pull it by hand and it breaks at the weakest node, leaving all the others steadfastly rooted. Each root or stem left behind can create a whole new plant. That’s why established runner grasses and their cousins in turf grass are so hard to remove permanently without chemicals.
Translocated herbicides such as Roundup remain perhaps the best solution to permanent running-grass removal because they kill right down to the root tips. The process takes about two weeks from the date of application to completely finish the job. The herbicide is applied to green leaves, which take it in through their natural processes. Then it moves throughout the rest of the plant. This ensures that no roots left in the ground will root and start the invasion all over again.
The more actively growing the grass is, the better it’s able to take up and translocate the herbicide thoroughly. Therefore, it must be applied during the growing season. If done in late spring, when the grasses are growing rapidly, they are still relatively small and easier to coat with spray. Some folks have discovered that watering and fertilizing plants and weeds before applying the herbicide helps the chemical to better enter and travel throughout the entire grass. When applied when grasses are becoming dormant or are already browned by frost, such an herbicide won’t work at all.
Removing an old lawn can be a challenge, but if you plan to take a month or more to get it done, you will find a much cleaner environment to begin a green, low-maintenance landscape.
First apply the herbicide to a growing green lawn. Do not water for a day or two after application to make sure the chemical remains on the lawn. Wait two weeks for full results. Once all has turned brown, dig out the remnants. Then till the area to bring everything to the surface that has been lying dormant. You may choose to water at this stage to encourage new growth for the second application of the herbicide.
While I am not keen on garden chemicals, runner grasses are an exception. Take your time in removing the old lawn and you’ll save yourself many hours of weeding in the seasons to come.