Visible timing varies by formula. Some products report wilting in as little as 20 minutes, many show visible action within about 1 hour, a few note noticeable effects by around 3 hours, and several list dead weeds within 24 hours. Expect variation by product and weed size.
They’re intended primarily for spot treatment around patios, driveways, walkways, pavers, and concrete, as well as in flower beds, raised planters, mulch beds, and around shrubs and trees. Specific product labels will list approved surfaces and any exclusions.
Product details commonly advise avoiding use on edible food or feed crops and, in some cases, lawns (depending on the formula). Labels also instruct protecting desirable plants during spot treatment. Always consult the product label for exact surface and plant exclusions.