Natural Weed Killers

I am sore.  It could be from all the hardcore gardening I did yesterday.  I pulled almost all of the broccoli and planted some scallions (I think that's what they actually are.  I always call them clump onions because I forget what they are really called and they grow in clumps and I used them like onions) and carrots, as well as moving some of the basil sprouting up under the lilac tree and rearranging the baby sunflowers under the dryer vent so it doesn't look so much like a two year old planted them (even though one did).

I'm pretty sure that it was the driveway that did me in though.  I really hate spending time, energy, and/or money on things that don't matter, like the appearance of the driveway (it's just a place to set a car when it isn't in use, for goodness sake!), but the latest newsletter from the trailer park indicated that they would like the driveways to be weed free and it did look pretty incredibly crappy in places, so I figured I should probably do something about it before someone complained and management either fined me or came over to "discuss it", in which case I'd be opening myself up for possible issues with the "over the top" garden as well.

I'd been kind of meaning to do something about the weeds in the driveway for a while, but it was one of those things that I wasn't sure what the best way to proceed, so I was procrastinating by waiting until I got a chance to research it.  I knew I didn't want to pour expensive toxic chemicals on it since A) we drink groundwater here so I didn't want to pollute our water, B) the kids play there, C) too expensive, and D) too close to the garden.  The other options I knew about were pulling them out by hand or pouring boiling water on them.  I didn't want to have to boil and haul that much water out, since you can see from the picture that it was getting quite bad in places, so I decided last night to start ripping them out by hand.  It wasn't difficult as far as weeding goes, since most everything had a really shallow root system, so they came out really easily, but all that bending and reaching and repetitive movement with my arms did a number on me! 

And I didn't even get it all done before it got dark (I started around 8:30pm, so I'm not really surprised)!  As sore as I am, I decided maybe I don't want to do the rest of it by hand, and still don't want to boil that much water, so here are some of the other options I'm now considering for the remainder of the driveway and for follow-up maintenance:

• Vinegar/water solution:  Is there anything vinegar can't do?  From what I've read, a mix of 1 part vinegar to 5 parts water ought to do the trick.  If I can find something laying around the house that would work well to distribute it, this probably will be my preferred method, since it is cheap and easy.  Looks like all you have to do for that one is apply it liberally every few days as needed until they die.
• Vinegar/soap solution:  I guess the soap helps the vinegar stick to the leaves and helps kill them, so this may be another path to pursue.  This would be a tad more expensive, since there's that soap element (I'd be using Dr. Bronner's of course!).  Looks like both of the vinegar solutions should be applied on sunny days, although I'm not sure why.
• Salt:  I've seen this listed by itself or in combination with vinegar.  I think I might add some salt to a vinegar and soap solution and see what it does, since the area I'm looking to kill weeds in is one that no one is ever going to want plants growing on.  If it wasn't, I wouldn't want to add salt to the area, since it might interfere with future plant growth as well.  In this case, that's a plus though!
• Citric acid/vinegar solution:  I have some of this laying around too, but I'm not sure I'd want to add citric acid, since it is the most expensive of the possible herbicides that I've discovered so far.
• Soap/water solution:  Looks like 5 tbsp liquid soap in a quart of water sprayed liberally on the weeds during the hottest time of the day (which is usually when I seem to want to do yard work anyway, for some reason!) should kill off plants within 24 hours.  If it doesn't, a stronger solution should within the next 24 hours.

So those are the options I'm looking at.  I don't think I have a spray bottle around right now other than the one holding my homemade mosquito spray, so I think I'll finish dealing with what I have in the driveway by hand, maybe pouring boiling water over just the weeds in the cracks in the sidewalk.  After that, I think maybe I'll spring for another spray bottle at the dollar store next time I'm in town so I can try some of these other ideas, probably using a vinegar/soap/water(/salt?) solution.

Have you used natural herbicides before?  If so, what and how did it work out?