I used vinegar on growing hairy bittercress in my yard. I have a lot of this weed all over. Vinegar for whatever reason does not seem to be killing it. Does vinegar take a long time to work or what? I want that weed dead before it explodes with all of those seeds.
Organic weed control products are non-selective, contact herbicides. They can also kill turfgrass and are not effective on mature or perennial weeds that have a substantial root system.
Household vinegar is not effective and horticultural vinegar can be caustic and cause skin and eye irritation. The assumption is that organic products are safe to use but that is not always the case. These products may kill some top growth but not get down to the root.
Here is our website on hairy bittercress with information on management. Take a look at conditions in your lawn that favor its growth. For example, mowing your lawn too short and shade. See our mowing practices http://extension.umd.edu/hgic/topics/mowing-grasscycling-lawns
Overseed in the fall to thicken up your turf.