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Kill weeds in large area - cover the weeds in tarp?

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  • Jul 20th, 2020 10:28 am
[OP]
Sr. Member
May 23, 2006
863 posts
94 upvotes
Vancouver

Kill weeds in large area - cover the weeds in tarp?

I cover a large area of weeds in cardboard and tarp.

Is that an effective way to kill weeds in large area? how long would it take?
10 replies
Deal Expert
Jan 27, 2006
15433 posts
8327 upvotes
Vancouver, BC
A dark tarp will work especially in hot sunny Summer conditions as it will basically bake everything under the tarp. However, since it will bake everything, you have to be sure that's the route you want to go.
Moderator
May 28, 2012
11087 posts
3240 upvotes
Saskatoon
It takes at least a month in the summer and you use clear plastic. Make sure the ground is level and water it just before putting the cover on. Secure it really well around the edges. Cardboard and mulch is good for areas such as perennial flower beds to suppress weeds but if you are looking at cleaning up a large planting bed, clear plastic is the way to go.
Deal Fanatic
Nov 21, 2013
5537 posts
3830 upvotes
dark tarp, not clear. Dark color will "attract" the sun, will be much warmer under, and will bake and make the plants to suffocate, including grass. With temperatures we have this summer I'd say it can take 1 - 1½ month, at least depending on how much sun it gets.
Deal Guru
May 29, 2006
10163 posts
2735 upvotes
just get a bottle or two of wilson weed killer hose attachment, it kills everything but the grass. i use it every year and it works awesome, it costs 12 bucks here in Alberta.
Deal Addict
Sep 8, 2017
3958 posts
4070 upvotes
GTA
Glyphosate (Roundup), and a pump sprayer.
Deal Addict
Feb 4, 2010
4054 posts
2817 upvotes
Do not use toxic chemicals as others have suggested. Use a DARK plastic tarp (even black garbage bags will work) don't use cardboard or newspaper - weeds generally stop germinating by August. You will still have dig out the dead weeds though. What do you do plan to do with the space after? If you leave the space as is, weeds will be back next year- you'll have to fill it with something.
Moderator
May 28, 2012
11087 posts
3240 upvotes
Saskatoon
Look up "clear or black plastic for solarization" and you'll get this:

In general, transparent or clear plastic is most effective for solarization, as the heating rays from the sun will pass through the sheet and be trapped to heat the soil below. Usually black plastic is less effective because it absorbs and deflects part of the heat, rather than trapping as clear plastic does.

from: Agriculture and Natural Resources, University of California

For years, I thought black plastic would be best but did some research a while back as was quite surprised that clear works better.

Solarization, when done correctly, will also cook some or most of the weed seeds in the soil...something that herbicides can't do.
Sr. Member
Sep 3, 2019
689 posts
417 upvotes
GTA
Used cardboard a few weeks ago with moderate success. It's my little used side yard though so low cost was my only requirement.

If you go this route, line up the edges with heavy objects to prevent wind from flipping them over.
Deal Addict
Mar 22, 2017
1221 posts
1248 upvotes
West GTA
Mars2012 wrote: Look up "clear or black plastic for solarization" and you'll get this:

In general, transparent or clear plastic is most effective for solarization, as the heating rays from the sun will pass through the sheet and be trapped to heat the soil below. Usually black plastic is less effective because it absorbs and deflects part of the heat, rather than trapping as clear plastic does.

from: Agriculture and Natural Resources, University of California

For years, I thought black plastic would be best but did some research a while back as was quite surprised that clear works better.

Solarization, when done correctly, will also cook some or most of the weed seeds in the soil...something that herbicides can't do.
I've heard that in early spring and late fall black works better because then the greenhouse effect isn't strong enough to bake the plants, and you benefit more from the light blocking of black tarp. In late spring through early fall, clear works better because plants will bake. I have no idea if that's true, I did read it online and it makes intuitive sense but I didn't bother - I used landscape fabric, planted through it, mulched over it, then the next year I removed the fabric.

On a lawn that obviously wouldn't work!

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