Mystery Weed in Garden Turns out to be Dreaded Pigroot

Q: Attached are pictures of a weed that I have been battling for the past few years in my garden.  It only occurs in my gardens, both vegetable and flower.  It appears where I break up ground where grass once was.  I need help in identifying it and how to control it or get rid of it completely. I use newspaper and mulch or straw to help control the weeds in my garden and that helps for those spots, but this weeds grows anywhere that is not covered. Because I rotate crops and move things around from year to year, the weed will reappear the following year on uncovered and unmulched ground. Can you help me with this?

C.L.

Republic

A: This is a weed called Red-Root Pigweed.  Red-root pigweed is a major weed problem in much of the area, especially in agricultural production because of its resistance to glyphosate.  Also, one plant can produce up to a million seeds which can build up in soil and be a problem for years to come. 

Once pigweed is established in an area it can be very difficult to control.  Hand pulling or using a cultivation tool when the plants are small and applying a pre-emergent herbicide listed for broadleaf weeds can be the most effective for homeowners. 

Here is a link about pigweed and plant relatives of pigweed: http://ipm.missouri.edu/MEG/2010/11/Worst-Weeds-2010/

Kelly McGowan

Horticulture Educator

University of Missouri Extension; Greene County; Southwest Region