Lisa from Glenmora, La writes
Princep Liquid Herbicide is a pre-emergent that will prevent weeds from germinating in the soil and will last about 4-6 months in the soil. It will not kill any actively growing weeds. Timing is always key when applying pre-emergents and will vary by region and the best person to ask about application timing is your local master gardener who works at your local cooperative extension office.
Answer last updated on: 08/27/2014