For all practical purposes anything that will kill weeds will also kill or seriously harm any other plants or grass. So no, weed killers have no role in gardening. Even vinegar, the most organic of weed killer kills other things too.

But there are other alternatives - solarization with plastic, covering the area with a thick layer of cardboard and mulch, skimming and flipping the surface soil, hoes, tillers, etc.

Dave

See the previous discussion from earlier this week linked below.

Here is a link that might be useful: Weed killers in vegetable gardens

Straight Vinegar. BUT, it will kill everything it gets on. So use caution.

I would agree with Greenthumb's suggestions. Don't make my mistake and use the construction CLEAR plastic/vapour barrier stuff though thinking it will kill the weeds. USE black plastic or GT's cardboard suggestion. My weeds thought they were in a green house and grew LARGER instead of dying:)
Vinegar will kill the critters, worms and various other great microbs, bacteria and what nots that live in and improve the soil.
You might also consider making a raise bed OVER the weedy area.

We have fought back persistent perennial weeds for several years, and we gain substantial ground each year by staying after them. Tap-rooted burdock and dock are especially un-fun, but with persistence, you can gain the upper hand.

For weeds in walkways and other places away from cultivated plants, I use boiling water. Once canning season starts, all the used boiling water goes on walkway and driveway weeds.

Well, if you want to kill all plant life in the area, you can mow (if needed) till, then water and cover with black plastic. Most seeds under the black plastic will germinate, then die. I have done this and it works well. It takes maybe 2 weeks. Earthworms and bugs are not harmed at all, at least for me in my climate. I did this in spring, so it wasn't that hot.

Solarizing with clear plastic is something that people do on lawns, and I believe it works, but I have never tried it. (I kill all my lawns by forgetting to water them). But anyway, to solarize a lawn, you water like crazy, then cover with clear plastic in the middle of summer for several weeks. The heat kills plants and most pathogens, too, supposedly. I don't think it would hurt mobile organisms like bugs and earthworms (I assume they would go deep during the day, and come up at night).

In any case, the plastic needs to be close to the ground for this to work. It isn't going to work if you have shrubs sticking up everywhere.

Black plastic works by totally excluding light, and maintaining favorable conditions for germination underneath. Black plastic will eventually kill any plant that needs light to survive, but for healthy shrubs, this may take much too long to be practical. Oh, and the coverage must be fairly complete. If light leaks in, the process will take longer or not work. Also, I don't think black plastic it will stop rhizomes or ground-creeping vines from snaking through the area.

Clear plastic works by raising the soil temperature extremely high so that most living organisms die. The high moisture is needed to let the heat permeate as deep as possible. There may be heat-loving decomposer type organisms at work in solarization, too. I don't know. If so, the moisture may help keep them alive. I have seen reports that it works even on Bermuda grass, so I assume it can kill rhizomes and vines. Of course the bermuda may start to spread back in once the plastic is removed.

--McKenzie