The best plan is still and sadly pulling them before they seed.  Especially if you want to garden organically.

Another less toxic option that works is using vinegar as an herbicide.  However, vinegar will still seep into the ground and expand its area of effect well beyond where you want.  For driveways, sidewalks, and street weeds, this shouldn’t be an issue.  But use caution when using it anywhere near where you have planted or want to plant.