Deadnettle (Lamium amplexicaule L).

Deadnettle is a cool season annual also known as Henbit and Henbit Deadnettle. It has the name “Deadnettle” because it looks like stinging nettles, but without the sting (hence the term “Dead”).

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

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

For more information, please check out our weed ID chart.

Deadnettle is a good indicator weed of cool, wet areas, and is in all States and Territories in Australia, including the ACT and Red Hill.

The distribution map for Henbit is courtesy of The Atlas of Living Australia.

Table Showing the Differences Between Deadnettle vs Henbit and Creeping Charlie.

Henbit Deadnettle Identification.

It is often mistaken for Creeping Charlie and Henbit:

• They all have hollow, square stems.
• They all have small purple flowers.
• The key difference is Henbit Deadnettle is an annual that flowers in the early Spring, and then dies in late Spring. Creeping Charlie is a perennial that flowers in the late Spring.

Henbit Deadnettle is a common, low growing weed that is very competitive in turf. There are fuzzy hairs and prominent veins on the upper leaf surfaces.

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

Category: Herb

Photosynthetic Pathway: Deadnettle is a C3 Weed.

Flower: Henbit Deadnettle has clusters of about 12 pink-purple tube shaped flowers. These are 1.5 to 2 cm long, and bloom in the Spring.

Height: Often grows up to 10 to 25 cm tall.

Leaves: Deadnettle leaves are 2 to 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: Henbit reproduces by seed, but it also spreads from stem fragments. New seeds are dormant, and require one or more Winters before they germinate.

• Seed longevity: >5 years.
• Seeds/plant: 200.

Comments:

• Deadnettle has a fibrous root system, with a taproot that is up to 20 cm long.
• It has soft, hairy stems, that emerge from the base of the plant.
• The stems are often purple, and the leaves are aromatic when you rub them.
• The upper leaves of Deadnettle attach directly to the stem.
• It is frost and drought tolerant, and tolerates partial shade.

Habitat: You find Deadnettle in disturbed sites, in fields, along roadsides, and also in lawns.

Being a Winter annual and biannual broadleaf weed, Deadnettle grows in periods of warm weather over the Winter. Henbit Deadnettle resumes growth and produces seed in the Spring, and then dies as temperatures increase in the late Spring and early Summer.

• Henbit Deadnettle quickly invades thin turf areas, especially if there is excess soil moisture. So deal with any soil compaction and improve the drainage.
• Plants are not affected by mowing, as it can have a prostrate growth habit.
• Maintain a healthy turf cover. Select a turfgrass cultivar suitable for your area, and then properly fertilize, mow, and irrigate to encourage 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. The best time to do this is when the pants are small, the soil is moist and before Deadnettle seeds.

If you don’t use a pre-emergent herbicide, early Spring vertical mowing and hollow-tine aeration will increase Henbit in thin turf areas. 

Always aim to implement cultural controls before you use herbicides for Deadnettle control. However, chemical control may still be necessary to manage this weed.

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

Pre-Emergent Control for Deadnettle.

Control of Henbit with a pre-emergent is best in the late Summer or early Autumn.

• Battalia 435
• Envu Esplanade
• BASF Freehand.
• Metolachlor

Post Emergent Control of Deadnettle.

• The ideal time for control with a post-emergent herbicide is when it is small and actively growing. This is typically in the late Autumn after the weed germinates, but before the temperatures begin to drop and plant growth slows (aim for an air temperature above 10° C).
• Apply chemical controls in the Autumn or early Spring for the best results. Keep in mind that herbicide effectiveness reduces as this weed matures.
• When you see Henbit flowering in the Spring, like other winter annual weeds, it is then very difficult to control. At this stage it is likely to be too late to prevent the production of viable seed.
• If you do make Spring applications make sure you do these before it flowers. A three-way herbicide is most common to use.

There are a few selective post-emergents that control this weed. Products that contain MCPA, and Dicamba usually provide the best results. Treatment is best over the entire area rather than spot treating.

• Dicamba. Do not use Dicamba on Buffalo grass.
• Warhead Trio. Safe to use on Buffalo grass.
• Stature Herbicide. Not for use in the home garden.
• QualiPro Negate. Not for use on Buffalo, but is safe on warm season turf grasses like Couch and Zoysia.
• Bispyribac Sodium in the USA.
• Foramsulfuron in the USA.
• Metribuzin
• Trifloxysulfuron in the USA.
• Iodosulfuron in NZ.

Non Selective Deadnettle Herbicides.

You cannot use any of these on lawns or turf areas to selectively remove Deadnettle.