Why You Should Never Apply Grass Seed & Pre-Emergent At The Same Time

Keeping your lawn in good condition takes year-round care. Applying pre-emergent treatment in the spring is crucial if you want to avoid clumps of crabgrass throughout the summer. You also need to overseed your lawn to keep it healthy and lush. Timing is everything if you want to do both of these things. Giving your lawn a dose of new seeds and pre-emergent at the same time will be nothing but a waste of resources since the herbicide will kill the young seedlings.

You can have both things on your lawn, but you must leave space between each treatment. If you apply the pre-emergent in early spring, you should wait until early summer before planting grass seeds. However, the type of grass you use matters; summer grasses can be planted in warmer weather, while cold-season grasses can't be planted until after summer. Weather is ever-changing, so you can't set the same date for pre-emergent and seeds every year; play it by ear and apply them as needed.

Pre-emergent is an herbicide intended to kill annual weeds in the grass family. You'll apply it in early spring before the weeds sprout, so they won't pop up later in the year. Applying it at the same time as turfgrass seeds can prevent them from emerging. The herbicides can damage turfgrass roots when they're young and cause them to die before they have a chance to grow.

Applying the herbicide a couple of months before you apply grass seed will solve this problem. If you use pre-emergent in the spring, you can safely overseed your lawn in the fall. Warm-season grasses can be planted in late spring or early summer; if you wait about two months after using pre-emergent, you should be able to plant grass seeds safely. Cool-season grass will most likely need to be put on hold until fall since late spring might be too late in the season to plant it.

Avoid pre-emergents labeled as weed-and-feed. It includes fertilizers that may cause cold damage to your grass or cause diseases to spread rapidly. If you want to plant cool-season grass in the spring, look for pre-emergents called siduron or mesotrione. These have been designed to kill crabgrass without hurting turfgrass. However, it's still an herbicide, and you should take caution when using it on your new grass.