When Can I Plant Grass Seed After Crabgrass Killer?

Crabgrass Killer

• Crabgrass killer is the trade name for MSMA, or monosodium methanearsonate. This is a spray designed for young, small crabgrass plants and does not generally kill mature, seed-bearing plants. MSMA will also not affect crabgrass seeds. Do not use MSMA on your newly seeded lawn, as it will harm new sprouts.

Preemergent Herbicides

• Because crabgrass grows rapidly and aggressively, preventing the seeds from sprouting is easier than controlling actively growing plants. Use a preemergent herbicide in early spring, before crabgrass seeds sprout. Plant lawn seed two to four months after using preemergent herbicides. Many homeowners wait until early fall to seed lawns, when temperatures and fading annual weeds enable new lawns to establish quickly.

Safe Herbicides

• Siduron is a preemergent herbicide safe for newly planted lawns. It will not harm or delay turf grass seed but prevents crabgrass and other annual weed seeds from germinating. Always read the label for proper application, as many manufacturers combine fertilizers and other chemicals with siduron.