How to Apply Pre-Emergent to New Lawns

Remove obvious weeds by hand when they first appear in a new lawn. It's common for weeds to appear in new lawns, even if the correct species was chosen for the space and the lawn was laid properly. Removing weeds by hand as they begin to pop up prevents them from becoming widespread, requiring the use of post-emergent herbicides.

Identify the weeds that are growing in your grass. Specific herbicides are required for specific weeds and grass species. Selecting the wrong one may fail to kill your weeds and could possibly damage your grass. Consult an expert if you're unsure of the type of weed growing. Pre-emergent herbicides include enefin, bensulide, dithiopyr, oryzalin, pendimethalin, and prodiamine, and they often come in combination to accomplish the killing of two or more weed species.

Test your sprayer before using with herbicide. Remove the lid and fill the sprayer with water. Pump up the pressure and test the shot by pressing the trigger down. Slightly untwist the lid to relieve pressure slowly. This also flushes out the sprayer from previous use.

Measure the amount of herbicide according to the instructions on the product. Pour the herbicide into the sprayer and tighten the lid to retain pressure.

Apply the herbicide the moment weeds appear, as the optimal time for application is 2 to 3 weeks prior to weed germination. Pump the handle to increase tank pressure. Spray the entire lawn until there is a visible layer of moisture on the weeds. Make sure all of the herbicide is gone from the sprayer.

Water the herbicide into the grass with a hose. Apply a single layer of water over the entire lawn, helping the herbicide to sink in fully.

Rinse the sprayer three times with clean water. Rinse over an empty dirt area, not a concrete area or other area where the leftover herbicide could run into a gutter.