STRAIGHT FROM THE HORSES MOUTH

Duane A. Lienemann
UNL Extension Educator

                   

     “What in the world is that ugly short plant with the purple flower”?  I have had that question brought to me several times over the last several years and it is not just homeowners with lawns that seem to be thick with that particular weed, but farmers also, who are finding it in cropland. I have written before about this weed, but it seems we need to revisit this problem. So here goes…. This “new” weed is normally found in thin and infertile lawns but this year seems to be everywhere. It has actually been around since the early 20’s when people think it came to Nebraska via contaminated grass seed.  This weed is called “Henbit.”
     Henbit in Yards and Gardens: Henbit is a actually a member of the mint family (lamiaceae) and is a winter annual with upright, square stems and pink-purple flowers. What makes this weed a “Winter Annual” is that it germinates in the fall, overwinters as a green plant, begins growing again in early spring, then completes their life cycle and go to seed in the spring or early summer. Normally it is more common to find this weed in lawns but this year we are seeing a lot of it in croplands, overgrazed pastures, and particularly in wheat fields or in fields that were in wheat last year.  
     Lamium amplexicaule, the Latin name for Henbit, is often confused with creeping charlie, Glechoma hederacea. Both have square stems and are in the mint family. Both have lavender to blue tubular flowers, however henbit flowers tend to be more on the purple/lavender range and are clustered at stem tips with clasping leaves below the flower cluster. creeping charlie flowers tend to be more in the blue range without the clasping leaves. Both plants have round shaped, scalloped leaves. A couple differences between henbit and creeping charlie include the life cycle and flowering time, and therefore control measures. Henbit is a winter annual and creeping Charlie is a perennial. The original creeping Charlie plants come back every year. Henbit has to start from seed each year. Henbit as a winter annual blooms very early in the spring and well before creeping Charlie blooms.  My guess you have noticed this purple color across town and fields and it has bloomed a little later than normal, and seems to be more prevalent than in previous years.
     Henbit can be highly competitive in newly seeded areas and thin or dormant turf. It is highly probable that the decline in lawns by drought lends to its appearance.  Henbit thrives in cool, moist areas. Growing conditions can be made less favorable by lightening the soil or otherwise improving drainage, especially in shady areas. Heavy, constant shade should be lightened as well where possible. Shady areas should be planted with turfgrass species which do well in the shade and which will provide maximum competition to weed species that invade these areas. Propagation of henbit is through seed. If it is already present in your landscape, you may prevent its spread by removal of the plant before it flowers and seeds.  Roots are fibrous, so it is easy to pull small plants up by hand or hand-hoe. If you hoe, be sure to dig at least 3 – 6 inches deep to remove the whole plant and its taproot. Maintaining a regular mowing schedule will also reduce plant populations. 
      Chemical Control of Henbit in Lawns: There are several effective chemical applications available to the homeowner for control of Henbit. The use of pre-emergent herbicides at the right time of year may help with control of this weed. Use a selective post-emergent herbicide taking care to follow spray intervals if treating newly seeded areas. Optimum control will be obtained when henbit is actively growing and in the seedling to flower stage of growth.  It is not easy to control this time of year.  The best time for control is in the fall, but we do need to control it now.  There are a couple of sprays that work.  The most commonly used and probably effective chemical is Trimec.  It can be put on your lawns to control henbit, chickweek, and clovers not to mention the easier killed weeds like dandelions.  You may have to apply it a couple of times, about 2 weeks apart for the best control. If you want to stop the seeds, you need to spray now.
     For the more adventuresome, you can mix your own spray.  One of the common remedies is 8 parts of 2,4-D mixed with 1 part of Dicamba based herbicide (ie. Banvel. Clarity, or Sterling).  A note, if you use the aforementioned mix, be sure to be careful of flowers and bushes that you want to keep as you could have some drift damage, so be sure to go out when there is little or no wind. Always read the label on the product to ensure safe application without harm to existing plantings. Please contact your local Extension office for recommendations of effective herbicides for controlling henbit and other troublesome weeds. 
     Henbit Control In Cropland and Pastures: By now the majority of henbit and purple deadnettle plants have bloomed or matured, consequently, there is probably very little to gain economically by spraying these with a post-emergence herbicide. Cultivation however will take care of these plants. Mature plants will eventually die back as temperatures become warmer. There is of course the thought of thousands of seeds that will be in the same spot in coming years. “Valor” may be used in a spring burn-down program with Roundup for burn-down control of henbit and chickweeds and residual control of waterhemp, common lambsquarters and black nightshade. Warning: It must be used 30 days before planting corn, so we are probably past the window of opportunity.  It also may be used for pre-emergence and contact activity in soybeans. Now in pastures, a newer product from Dupont works well. “Cimarron” not only will get the Henbit but a lot of other weeds in pastures including musk thistle, common mullein, prostrate spurge and even marestail. 

 The preceding information comes from the research and personal observations of the writer which may or may not reflect the views of UNL or UNL Extension. For more further information on these or other topics contact D. A. Lienemann, UNL Extension Educator for Webster County in Red Cloud, (402) 746-3417 or email to: dlienemann2@unl.edu or go to the website at: http://www.webster.unl.edu/home