Deadnettle (Lamium amplexicaule L)

Deadnettle is also known as Henbit Deadnettle, and earned the name of “Deadnettle” because of its resemblance to stinging nettles, but without the sting (hence the term “Dead”). Henbit Deadnettle has hollow stems that have a square cross section, is opposite leaved, and hairy.

It is a common, low growing, annual or biennial weed that is very competitive in turf areas. Deadnettle can also cause staggers if livestock eat it, with sheep being the most susceptible.

Deadnettle germinates from winter to spring, and is found in all States and Territories in Australia, including the ACT and Red Hill.

Being a Winter annual, it means it germinates in the Autumn, survives over Winter, and then flowers and develops seeds. Once temperatures rise in the late Spring and early Summer it dies off.

For more information, please check out our weed ID chart. Deadnettle is a good indicator weed of cooler, wetter areas..

 After you finish reading this, you will be able to:

• Identify Henbit Deadnettle or Deadnettle.
• Know the habitat of Henbit Deadnettle.
• Know the best cultural and chemical options to control Henbit Deadnettle or Deadnettle.

Deadnettle Identification.

Category: Herb

Flower: Has clusters of about 12 pink-purple tube shaped flowers, that are 1.5-2cm long, and it blooms in the Spring.

Height: Often grows up to 10 – 25 cm tall

Leaves: The leaves of Deadnettle are 2 – 3 cm in size. They are opposite in pairs, and each pair of leaves is at 90° to the pair below it. It does not form a rosette.

Reproduction: Reproduces by seed.

Root Sysyem: It has a fibrous root system, with a taproot.

Comments: Deadnettle has soft, hairy stems, that emerge from the base of the plant. The stems are often purplish in colour and the leaves are aromatic when you rub them. A good way to identify this weed, is that the upper leaves are generally more purple-red than the lower leaves.

Habitat: It is common in open disturbed sites, often in fields and along roadsides, and it is also found in lawns.

Being a Winter annual and biannual broadleaf weed, Deadnettle grows during any period of warm weather over the Winter. Other than unusual warm weather periods, it remains dormant during the Winter. Henbit Deadnettle resumes growth and produces seed in the Spring, and then dies as temperatures increase in late Spring and early Summer.

Henbit Deadnettle quickly invades thin turf areas, especially where there is overly moist soil. Shade also encourages growth. Its growth habit may be prostrate, so plants are not affected by mowing.

First, select a turfgrass cultivar adapted for your area, and then properly fertilize, mow, and irrigate to encourage dense growth. Water the lawn deeply but as infrequently as possible in the Autumn, as weed seeds need soil surface moisture to germinate.

You can pull small numbers by hand.

Implement cultural controls before applying herbicides for Deadnettle control. However, chemical control may still be necessary even if you modify your  lawn care techniques to further reduce the population. Apply chemical controls in the Autumn or early Spring for best results. Keep in mind that herbicide effectiveness reduces as this weed matures.

Also, as it it is a winter annual, it will naturally die in the summer so you probably don’t need to apply herbicides in the late Spring. You can see heat stress kicking in when the leaves start to turn yellow.

There are a few selective post-emergents that control this weed. Products containing MCPA, and Dicamba usually provide better results.

We recommend 2,4-D amine 625, and Dicamba 500 (Do not use Dicamba 500 on Buffalo grass). Treatment is best over the entire area rather than spot treating.