Timing and Choosing Pre-emergent Weed Preventers, Spring and Fall

Pre-emergents (weed preventers) are applied to the landscape to prevent seeds from germinating.

The key is the timing. Pre-emergent herbicides MUST be applied BEFORE summer weeds (crabgrass, etc) seed germinate.

In general, to get good summer weed control in Atlanta you should apply a pre-emergent on March 1.

For winter weeds (annual bluegrass, henbit or chickweed) the apply date is September 15.

If you want specifics: Weed scientists use soil temperatures to determine the trigger point for their application of pre-emergence herbicide.

Crabgrass seeds germinate when spring soil temperatures tend upwards from 55 degrees F. 

Annual bluegrass starts germinating in late summer or fall as soil temperatures fall below 70°F.

The University of Georgia College of Agricultural and Environmental Sciences oversees a network of 50 weather stations across Georgia. Click here to chart your own soil temperatures.


Pre-emergents for lawns. Some prevent both grassy weeds and broadleaf weeds:

benefin (Amaze, Balan, Crabgrass Preventer ) click for sources

oryzalin (Surflan) click for sources

pendimethalin (Halts, LESCO 0-0-7) click for sources

dithiopyr (Bonide Crabgrass and Weed Preventer, Dimension, Preen Crabgrass Control)  click for sources

prodiamine (Barricade)  click for sources

isoxaben (Gallery) click for sources


Pre-emergents for Ornamental Beds (not lawns)

Trifluralin and isoxaben (Preen Extended Control ) click for sources


Pre-emergents for Ornamental Beds and Vegetables

Trifluralin (Preen Garden Weed Control) click for sources


PRE- and POST-emergent combo products for lawns

Prodiamine and sulfentrazone (Bonide Weed Beater Complete) click for sources

Quinclorac and dicamba (Ortho Weed B Gon with Crabgrass Control) click for sources

Isoxaben, mecoprop, dicamba (Bayer Season Long Weed Control) click for sources


REMEMBER: Read all herbicide labels thoroughly to be sure the product can be used on your particular turfgrass and that it controls the weed(s) you are trying to manage.

annual bluegrass in bermuda