Is this a familiar sight? Bermuda grass is the bane of this gardener. Typically, directions for development of raingardens in native soil are to check permeability, clear the site, till in compost, and plant. But digging up sod in Illinois is different than removing the grass in Oklahoma.
Our primary grass seems to be Bermuda and it is invasive! Bermuda spreads not only by seeds but also by runners above and below ground. It can overtake over a foot of garden in a growing season. So, simply taking off the top layer of sod won't do. You have to kill it.
But how? I checked with the County Extension Office office for some direction. And their advice confirmed my anecdotal experience: Bermuda is tough stuff. You can try thermal sterilization of soil - putting down black plastic and allowing the sun's heat to kill everthing off. This kills the surface plants but doesn't address the deeper roots, which can be six inches or more below the surface. This also kills plants by depriving them of sunlight, but Bermuda can stay dormant under the soil for an extended period of time. I've also tried herbicides, which seem to work for a while, but Bermuda always seems to come back.
Bermuda, it seems, must be killed and killed again. They say up to 6 or 7 sprayings over time are necessary to really eradicate Bermuda from a proposed plot. And that takes planning ahead, about a growing season ahead, of when you want to plant.
And because it continues to spread from the outside, placing a good quality edge to 6 inches beneath the soil (not extending above the ground) will help minimize root intrusion. Surface runners take a hands-on approach. After all that, you should have a garden that is much easier to maintain. But it takes some time and planning (and a bit of grass-killer).
