Ortho WeedClear Lawn Weed Killer Concentrate states to use 2.5 oz per gallon of water for every 400 square feet
Ortho WeedClear Lawn Weed Killer Concentrate label instructs product should be applied when the weeds are small and growing in the spring or fall. Crabgrass, large and smooth- Apply in the spring before crabgrass is 4 inches tall or when crabgrass is first noticeable in the lawn. Make a second application after 3 weeks for dense weed populations. Most selective herbicides wont work below 55 degrees. For the best times to apply in your area we recommend conatcting your local extension office.
