Last fall my family and I set up a number of key hole lasagna gardens. Once the snow lifted and we had a peak in the ground we were delighted at the quality of soil left behind as well as with the quantity of insects that were taking up residence. Despite our laying down cardboard, as soon as the spring rains hit there was grass everywhere! It's taking over and I'm not sure what to do. Someone suggested chopping and dropping it and then mulching heavily in the fall to take care of it but I'm not convinced that that will work. Grass can be so vigorous and invasive. I'm here looking for a second opinion. Any and all help would be greatly appreciated. Thanks you!
It sounds like the grass seed was in the mulch, the fastest thing you can do if you have the weather for it is solarize the grass with black plastic. In that heat and lack of light they will die off and shrivel up the roots. It's not the greatest thing for your bed's soil life but neither is a grass garden. You could try flipping it and all sort's of things, but if it's really from the mulch, new seeds will keep germinating in waves. I made that mistake long ago, now i only mulch with hay that is rotten. If it's not the hay seed it's something else, the method still works in hot weather. I tried it with clear plastic in boggy ground and it failed, the plants had enough light to pump the ground dry sweating into the plastic.
If you have enough mulch, just mulch it heavily. Do not cut the grass! If you cut it, new shoots can just start growing even if you mulch it. I never cut existing vegetation when making no dig beds, i just mulch it. Let the grass be and just mulch it, that way it will take lots of energy from the roots. Then you have to look for shoots of grass when they appear. The most effective way here is that i just put more mulch on it or if i don't have mulch i push the vegetation under existing mulch. How many mulches in this post, haha. Have a good time!
There's grass and then there's GRASS
Do you have lawn? Near the garden? Any idea if it's 'running' or 'clumping' grass?
Running grass can be a nightmare. I suggest digging around in the lawn and new bed. See any horizontal, fat, pale roots?
If so, stop! Cutting just encourages running varieties
I think grass is a total pain (but I have no HOA, kids, or dogs...)
Spraying the grass with a light mist of veggie oil will kill it real quick. Within the week it should be dead and drying out. the oil will break down in the soil with no issues and the soil life won't suffer. Oil will prevent respiration and will also magnify the heat and light from the sun, thus burning it while it suffocates.