If you can clean the stuff out of the cracks, you can backfill them with crushed stone. Many home building centers sell an epoxy that can be used to set the stone dust.

If you don't like the idea of epoxy between the stones- then you're stuck with periodic treatment with vinegar, etc.

Filling with stone isn't an option. The cracks were already fillled with gravel and the weeds grew right through it w/o a problem. Looking for a simple solution and so far it seems like mass amounts of vinegar to prevent them from growing back is the best solution. Either that or spreading sulfur in the cracks.

Crushed stone, or maybe sand- might be able to get it to fill in a bit, then set in epoxy

Mix a bunch of salt with water, make up a good strong batch, and pour/spray it on the weeds, they'll be done by the next day.

Salt is ok to kill weeds but not to prevent them, I would think, because the salt would wash out probably even quicker than the vinegar once rainwater hits it..

but then again, salt is very easy to spread.....hmm..this is a good idea, might consider it instead of vinegar

Something is going to grow in the cracks, so crowd the weeds out by planting something pleasing instead. I have creeping thyme and violets volunteering between pavers where I had potted plants sitting last year. I like it much better than the grass that was trying to take over, so I'm going to spread seeds deliberately when I finish my patio this summer.

Catherine

It won't help to prevent those seeds from germinating, but once the weeds are there, you can pour boiling water on them to kill them immediately. It saves on the nails and fingers. I always pour my leftover corn water on our brick walkway.

Corn gluten is very effective as a preemergent and is organic. I put in a stone terrace around my new house a year ago, and planted a variety of low thymes, Armeria, small dianthus, etc. in between the stones. But to keep down grass etc, I applied corn gluten liberally. It worked very well.

The thyme is a good idea. I've heard of packing lime dust in between the pavers. I guess this stuff packs tight enough to prevent most weed emergence and maybe even raises pH high enough to delay germination. Who knows, but it seems like a viable option.