Killing weeds with black plastic - Ask Extension
Hi. I do not have any grass in my yard, but do have what seems like bzillions of weeds. Last year, I covered part of some paths with heavy 6ml black...
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Killing weeds with black plastic #855281
Asked November 14, 2023, 3:42 PM EST
Hi. I do not have any grass in my yard, but do have what seems like bzillions of weeds. Last year, I covered part of some paths with heavy 6ml black plastic and left it there until Summer. It helped somewhat and no weeds grew in those areas during the Summer after I removed the plastic. This year I am late in doing anything. Weeds of various types are already at least an inch high and cover much of the paths. Is it too late to put the plastic down once the weeds have started coming up? Would the weeds that are under there remain alive and then continue to grow once I removed the plastic in Summer? I could try to remove the weeds with an anchor hoe before putting the plastic down, but that would be a huge job. Help!!!
Thank you.
Lane County Oregon
Expert Response
If you are trying to create fairly permanent, weed- free paths, then yes, you can do that now.
The problem with your previous effort is that you removed the plastic
when grasses and weeds are going dormant for the dry summer anyway. Come fall, and rain, any surviving bits leaped into growth.
The key is to leave the plastic in place, and put a mulch (like wood chips) on top of it. Mow the weeds as short as you possibly can, cover with the plastic and mulch, and leave it in place. No weeds will grow through. Some may escape around the edges, and of course, some may seed into the mulch, but it will greatly reduce the maintenance needed.
If you want to kill weeds in a non-path area, the same thing applies, but leave the plastic on through the winter and well into the spring growing season. Then pull up a bit, water the ground, and make sure nothing is still alive before pulling it all up. You can also use a "smother mulch" of newspaper or cardboard topped with mulch. This is effective and doesn't need to be removed, but over a large area can temporarily reduce soil oxygen and possibly cause harm to soil life.
A deep mulch of arborist's wood chips is even better.
The problem with your previous effort is that you removed the plastic
when grasses and weeds are going dormant for the dry summer anyway. Come fall, and rain, any surviving bits leaped into growth.
The key is to leave the plastic in place, and put a mulch (like wood chips) on top of it. Mow the weeds as short as you possibly can, cover with the plastic and mulch, and leave it in place. No weeds will grow through. Some may escape around the edges, and of course, some may seed into the mulch, but it will greatly reduce the maintenance needed.
If you want to kill weeds in a non-path area, the same thing applies, but leave the plastic on through the winter and well into the spring growing season. Then pull up a bit, water the ground, and make sure nothing is still alive before pulling it all up. You can also use a "smother mulch" of newspaper or cardboard topped with mulch. This is effective and doesn't need to be removed, but over a large area can temporarily reduce soil oxygen and possibly cause harm to soil life.
A deep mulch of arborist's wood chips is even better.
