Wednesday, May 17, 2006

Solarizing and Vinegar: organic weed control

For weed control nothing beats solarizing. It's cheap--$12-13 for a 4' x 50' roll. It's easy, organic and it definitely works!

We have lots of bermuda and foxtail grass and I have begun solarizing in earnest this year to help keep things better until control.

For small, spot weed control, full strenth vinegar works as good as RoundUp. This works on tender leafed plants. I keep a spray bottle handy. Works good around rocks, brick pathways, etc. For serious weed control go to Solarization.

To try solarizing:

  1. Buy 4' x 50' rolls of CLEAR medium to heavy plastic (3-6 mil) at the hardware store. Anything larger is too cumbersome to work with.
  2. Thoroughly wet the area you want to rid of weeds, harmful bacteria, insect larva, etc. The deeper the ground is soaked the better.
  3. If you want to take the extra step of loosening up the soil, this is recommended, although I have not tried this yet.
  4. Unroll the plastic and lay it out flat. It's handy to have an extra person (if you can find one).
  5. Lay it on the area you want to solarize.
  6. Put something around the edges to hold it down. Anything handy, but the more you 'seal' the edges the better it works. I use old garden 2x2's from past tomato cages, etc.
  7. Go do something else for a week or until everything looks really dead under there. The more sun the area gets, the better. If you slide your hand under the plastic after a day or so, you can feel how hot it is under there.
  8. For thorough pasteurization of the soil, you can leave it on for 4-6 weeks. The best time to solarize soil is in the hot summer months of course. If it rains during this time, simply sweep off the puddles. Don't punch holes in plastic.


  1. Vinegar is absolutely not as effective as Roundup. That's simply impossible, given the chemistry involved. It may kill some small plants, but not as effectively as Roundup will.

    Solarizing your soil is a fine weed killer as long as you are willing to kill everything else living in the soil, including beneficial bacteria, at the same time.

    The reason clear plastic works better for solarizing than black is that it admits UV radiation and then traps it, like a greenhouse. Unvented (you must seal the edges down well) it heats up really fast in direct sun and kills everything under it. The black plastic doesn't transmit UV radiation; it just absorbs and re-radiates heat to the plants underneath, which is less effective.

  2. I realize that I left out an important step for solarizing!

    The ground should be thoroughly wet before laying on the plastic.
    Although it has worked well for me without the soaking, I am taking this extra step now.

    I have update this post on the instructions for solarizing. Sorry for any negligence on my part, but I am still learning too

  3. I have found that using black plastic is far more effective that clear plastic. The clear plastic allowed the light and heat to make the plants grow faster. They just pushed the plastic up. Disclaimer: I live in Minnesota, but it does get hot here (it's about 95 today). My garden is carved out of a former quack grass field. It took a full season of tarping to kill the quack grass, but when I rolled the tarp up the next Spring, it was the richest, blackest most friable soil I've ever seen. The earthworms (which are not native here and considered an invasive species in our woodlands) and other critters soon returned. I think many of them go deeper in the soil to avoid the heat.

  4. I would be interested in hearing other peoples experience with vinegar. I've heard you need to use a stronger acidity than what is sold in the grocery store(maybe 20%??)

    Nothing is as good as RoundUp for killing things, but I'm not sure that is the point. Gardening teaches me that in the long run we can't control nature. At best we can only guide it along a little (and I have to confess that I have to keep relearning this lesson) Vinegar is considered an organic weed control. RoundUp certainly isn't.

  5. I purchased a product called "Perfectly Natural Weed and Grass Killer". It is clove oil and vinegar. So far, it's working well, though for some perennial weeds, like thistle, I have to hit it twice, but I expected that. It is expensive but I think has a fairly strong vinegar ingredient, stronger than the 5% of "household strength vinegar.

  6. Store strength vinegar is not choice for this. Higher acidity strength is much more useful. BUT vinegar is NOT allowed in certified organic control of weeds, yet.