Friday, July 8, 2011

Preen for Garden Weed Control -- Just what’s in that stuff anyway?

 Preen herbicide has long been used in home gardens for preemergence control of many annual weeds.  The active ingredient, trifluralin, is labeled for use around many woody and herbaceous ornamental plants as well as many vegetable and fruit crops.  Although, not the most efficacious herbicide, Preen controlled many of our most common landscape weeds including henbit, chickweed, oxalis, crabgrass, and annual bluegrass, without injuring landscape plantings.  This product is still widely available in garden centers throughout the country.  However, look closely at the label – the Preen you purchase today may not be the same product you previously used. 

Today the Preen name is used to identify a diverse product line that includes preemergence and postemergence herbicides.  Several Preen products contain 2,4-D for broadleaf weed control in lawns; these products should not be used in landscape beds.  The active ingredient in Preen Weed Preventer for Southern Gardens is dithiopyr – the same ingredient found in the herbicide Dimension.  This is safe on most ornamentals but should not be used around any food crops. There is Preen Mulch Plus Premium that contains isoxaben plus trifluralin (think Snapshot TG); not to be confused with Preen Plus Mulch Midnight Black that contains trifluralin (but no isoxaben).  The isoxaben-containing mulch will damage pansies but the trifluralin-containing product will not.  Confused yet?  There is also Preen Brush Weed Killer that contains 2,4-DP + 2,4-D + dicamba; Preen Weed and Grass Killer that contains glyphosate (same ingredient as Roundup); and an organic product for vegetable gardens, Preen Vegetable Garden Weed Preventer, that contains corn gluten meal.  Many different active ingredients, all sold under the Preen name can lead to confusion. 

So, if you go to the garden center to purchase Preen for weed control in your garden or lawn – READ THE LABEL.  Make sure you purchase the right product for the right job. 

Labels and material safety data sheets for the Preen products are available from the manufacturer’s web site at

Written by: Joseph C. Neal, Professor and Extension Specialist -- Weed Science


  1. The weeds are the unwanted plants that grow naturally. No One actually wants them to grow in their lawns and gardens because these weeds destroy the natural look of the garden. Thanks to weeds control fabric because these fabrics have controlled the growth of weeds naturally with out any side effects. The website weed control fabric offers the best quality over the internet.


  2. I spent most of my earth day in bed. I was working at a flower garden and I was left instructions to spread preen in the garden. After I spread the product within minutes I was sick at first I did not know it was the Preen so I returned to the garden. I literally fell to the ground and started to throw up. I had to leave immediately and spent the rest of the day in bed sick. I was shocked that this had such a harmful effect on me. BAD NEWS-ugh