Do You Water in Pre-Emergent?Updated 2 months ago

Yes, you must water in pre-emergent herbicides for them to be effective. Pre-emergent herbicides create a barrier in the soil that prevents weed seeds from germinating, but they need water to activate and move into the top layer of the soil where weed seeds are present.

How Much Water is Needed?

Most pre-emergents require about ½ inch of water within 48 hours of application. This can come from:

• Irrigation (sprinklers or hose)
• Rainfall (natural watering)

What Happens If You Don’t Water It In?

If a pre-emergent is not watered in, it will remain on the soil surface and break down from sunlight, becoming less effective. Without proper activation, weeds may still germinate.

Best Practices for Watering in Pre-Emergent

• Check the product label for specific watering requirements.
• If no rain is expected, run sprinklers or irrigation within 48 hours of application.
• Avoid overwatering, as excessive moisture can dilute the product and reduce effectiveness.

Bottom Line

For the best weed control, always water in pre-emergent herbicides after application. This ensures the product moves into the soil and creates an effective barrier against weeds.