Weed Poison Alternative

I am responsible for keeping a gravel parking area looking nice.

There are many weeds that grow in it; mowing them is out of the question because of the gravel.

Last year I sprayed them with weed killer multiple times - it's not a permanent solution unless I applied a "No Grow" poison.

I would like to not use poisons etc., but I also need to keep the area looking nice.

Any suggestions?

You have to either change the land (poison, salt,  pavement), maintain it (temp poisons, weed burner, strong vinegar, weed puller) or live with the weeds.

That's what I was afraid of.

Would salt be the least toxic way to permanently (somewhat) stop growth?

Adding a decent layer of clean gravel every year after evening out the new "sub-layer" will help: the gravel will move around a lot and slowly disappear. Wherever soil's exposed, stuff'll grow. Organic matter and seeds will blow in whtever you do, so I think you'll find it a real challenge managing it organically to 'conventional' aesthetic standards, and one reason why glyphosate's so popular!                 

Too much gravel and people get stuck.

Salt is not an environmentally friendly option unless you live right next to the ocean.

Of course, potential vehicular  stickage!
Maybe check the maximum recommended grave depth in a carpark and ensure that's maintained.
All theory though...
Industrial-strength vinegar is relatively effective.  It doesn't kill roots though, so you'd need to pull any biguns at the start, then hopefully spraying will keep on top of the littlies.

How about a propane weed burner? My husband got me one for Christmas after I wouldn't let him spray round-up on our gravel driveway last year!  I can't wait to try it.

Thanks, I'll look into that.

In a situation like that, the propane burner is probably your best option.  Just make certain that you fry each and every one before it goes to seed.  (Most weed seeds can survive a forest fire!)  You cannot control seeds brought in by the winds and bird poop, but if you can control the existing weeds before they reseed, it can be a manageable task.  Every time you need a break, just tell the boss "I gotta go check the parking lot...I thought I saw some birds setting up camp there!"