What's that purple weed?

April 20, 2016 1:25 PM

I’ve received a few questions asking what the purple weed is that is appearing in the landscape. It is probably either purple deadnettle (Lamium purpureum) or henbit (Lamium amplexicaule).

These weeds often get confused because they look similar. They both belong to the mint family, have square stems, have an ascending growth habit, opposite leaves, purple/pink flowers, and are winter annuals. When trying to identify if you have purple deadnettle or henbit, key ID traits to tell them apart are listed below. 


Purple deadneetle that was found in Van Buren County this spring (2016).
Photo taken by Nancy Carr

Key ID traits for purple deadnettle:

  • Purple-tinged leaves on upper stem triangular with pointed tips
  • Upper leaves with petioles, not directly attached to stem

 


Henbit may look similar to purple deadnettle, but there are some key ID traits to look for to tell these weeds apart. 

 

 

Key ID traits for henbit:

  • Leaves rounded with deep lobes and venation on upper stem
  • Upper leaves directly attached to stem with no petioles
  • Densely pubescent (hairy) leaves

Since both are winter annual, preventing seed production is key to management. Tillage and herbicides are effective management options for these weeds. Both species are flowering now and management with herbicides will not likely result in full control. Fall or early spring herbicide applications will be most effective at managing problem infestations. Contact your local Iowa State University Extension & Outreach field agronomist for resources regarding control of these weeds.

Another weed that belongs to the mint family and is making lawns appear purple right now is ground ivy (Creeping Charlie). Unlike henbit and purple deadnettle that are winter annuals, ground ivy is a perennial weed, and also generally stays confined to lawns. 

Additional references:

Purple Deadnettle

Henbit

Ground Ivy

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Rebecca Vittetoe Field Agronomist in SC Iowa

Rebecca Vittetoe is an extension field agronomist in southeast/south central Iowa. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.

Areas of expertise include agronomy, field crop production and management of corn, so...