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Closeup of the center and partial petals of a deep yellow sunflower.

Pre-emergent Versus Post-Emergent Weed Control

We have lots of folks asking about the difference between treatments that claim control over annual broadleaf weeds like spurge versus post emergent weeds like dandelions.  This is often a very confusing distinction which only requires a brief explanation to clear things up and understand the differences between the two.
Annual broadleaf weeds germinate beginning in late April and continue throughout the summer.  The crabgrass suppression treatment often used to begin the season will inhibit crabgrass and these annual broadleaf weeds as well.  Therefore, these weeds have not and don’t even germinate because of this first treatment in many lawn programs.  This type of treatment will not control existing weeds like dandelions or clover.  A subsequent treatment which targets perennial or biennial broadleaf weeds works completely different by attacking the plants you see in your lawn right now.  This is done by contact with the leaf surface and by absorption into the root system.
Although there are some annual broadleaf weeds which will germinate later and not be controlled by the first treatment in April or May, subsequent broadleaf weed treatments in a post-emergent setting will address those villains.  Another option to naturally reduce broadleaf weeds involves turf building by adding compost tea, kelp, annual aeration/overseeding, lime, as well as natural or organic fertilizer.  A healthy lawn that is thick and growing will naturally crowd out a huge amount of weeds over time without the need for broadleaf weed control treatments.  However, many folks like to speed the process up by having a few select weed reduction treatments followed up by a conversion to natural treatments afterward.
So, if you are confused about pre-emergent weed control versus post-emergent weed control, I hope you feel a little better after reading this short blog post!  Have a great spring and don’t fear, “Mrgrass” is always near!