Can I Apply Pre-Emergent and Seed at the Same Time?

When fall rolls around, many homeowners look forward to two important lawn care tasks: preventing pesky weeds from taking over and planting fresh seed to thicken up their turf. But here’s the big question we often hear: Can I put down pre-emergent and seed at the same time?

The short answer? Not if you want your new grass to grow. Here’s why, and what to do instead.

Pre-emergent herbicides are designed to create a barrier in the soil that prevents seeds from germinating. That’s perfect for stopping weeds like crabgrass and poa annua—but it will also block your desirable grass seed from sprouting. If you apply both at the same time, your new grass seed will struggle to grow, leaving you disappointed with thin or patchy results.

Fall is an excellent season for seeding because of cooler temperatures, consistent rainfall, and less weed pressure. To get the best results, you’ll need to choose which goal is most important this season:

• If your lawn needs new seed: Skip the pre-emergent. Instead, focus on aeration, seeding, and feeding your lawn with a starter fertilizer that supports germination, such as New Lawn Starter 20-27-5 or EcoFusion™ Starter 16-21-4. Once your grass is well established (usually after the second or third mow), you can begin to use selective post-emergent weed control if needed.

• If your lawn is already thick and healthy: Skip the seed and go with pre-emergent, such as Barricade®, Barricade® Plus Lawn Food 18-0-4 or Crabgrass Preventer Plus Lawn Food 26-0-6. This will stop grassy weeds from sprouting and keep your lawn looking clean and uniform through fall and into next spring.

Always refer to the product labels to ensure they are suited for your grass types and the weeds you are treating.

If you’d like to do both, you’ll need to separate the applications. Seed in the fall to give your lawn a strong start, and then plan on applying pre-emergent early in the following spring. That way, you’ll get the best of both worlds: a dense, thriving lawn and fewer weeds.

Whether you’re seeding or protecting, feeding your lawn with the right fertilizer is key. A starter fertilizer high in phosphorus helps new seedlings establish strong roots, while a balanced fertilizer, such as Core™ 12-8-12, supports established turf preparing for winter.