Asthma Weed (Euphorbia hirta)

Asthma Weed is also known as Hairy Spurge or Cats Hair. Hairy Spurge is an annual soft leaved plant, that produces a few spreading to almost upright reddish stems. It usually grows up to 40 cm tall, and its stems have a cover of yellowish hairs and contain a milky sap.

The sap is toxic on ingestion and highly irritant externally. It causes photosensitive skin reactions and severe inflammation, especially on contact with eyes or open cuts.

You often find Asthma Weed in turfgrass or in mulched planting beds. However, you can also find it growing in sidewalk cracks and between patio pavers.

Being semi-tropical and tropical warm season weed,  Asthma Weed does not tolerate frosts and prefers warm and sunny locations. It also grows in dense shade.

Asthma Weed has its name because it treats asthma and several lung diseases. This plant is effective against several diseases, such as worms, dysentery and colic, warts, asthma, bronchitis and dengue fever.

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

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

• Identify Asthma Weed and Hairy Spurge.
• Know the habitat of Hairy Spurge or Cats Hair.
• Know the best cultural and chemical options to control Cat’s Hair.

 

Asthma Weed or Hairy Spurge is an annual stemless or short stemmed weed. It has tap root and a basal rosette of leaves about 500 mm wide. As it grows, it sends out stolons and quickly spreads across the ground.

It has one a main taproot is up to 60 cm long but is usually around 15 to 20 cm long. The rest of the root is made up of secondary fibrous roots that grow off the main taproot.

Category: Broadleaf (Dicot).

Photosynthetic Pathway: C4 Weed.

Flower: Hairy Spurge flowers from Spring to Summer. The flowers are in the upper leaf forks. These green/yellow/creamy coloured flowers look like dense rounded clusters.

Height: It grows up to 40 cm high.

Leaf length: It has paired leaves which are 4 to 50 mm long. These leaves have a dark green/red colour with purplish markings. They are on short stalks about 1 to 3.5 mm long, and have a fine-toothed margin.

Leaf width: Leaves are 2 to 24 mm wide.

Reproduction: Asthma Weed reproduces by seed, and creeping stems that root at the stem joints. When the seed pods mature they explode to disperse the seeds.

A mature plant produces several thousand seeds over the course of just 8 to 10 weeks. It germinates best at temperatures between 24°C and 29°C, but germination occurs at any time temperatures are over 16°C.

This coupled with a life cycle that takes only about 60 days from germination to seed setting, means the population can rapidly build up.

Comments: Both the upper and lower leaf surfaces have a cover of close-lying hairs. As the plant matures it loses the upper leaf hairs.

Habitat: Hairy Spurge is a weed of verges, footpaths, lawns, bare areas, and playing fields.

Asthma Weed is a good soil indicator weed of compact soil, and bare or thin lawns. For more information check out our weed ID Chart to Identify Weeds by photo.

 

 

 

You can control Cat’s Hair by cultural and chemical means.

 

 

 

Repeated hand weeding is effective but you must remove all the roots of Asthma Weed, and dispose of them to avoid re-growth. Hand weeding must be done regularly say every 2 to 4 weeks because of this plants fast growth rate and its ability to quickly produce seeds once it germinates.

 

 

 

Due to its low prostrate growth habit, mowing is generally not an effective management tool for Asthma Weed.

 

 

 

Asthma Weed thrives in thin or bare areas so grass selection is important. Factors such as shade, play an important role in this, as to does the climate and amount of wear..

 

 

 

Most broadleaf herbicides will control this weed, although registered options in Australia are limited. We have personally had succss using ProForce Warhead Trio which gave results in 2 weeks.

Pre-Emergent Control of Asthma Weed.

There are currently two options with a Hairy Spurge or Asthma Weed registration in Australia. These are BASF Freehand and Envu Esplanade.

• BASF Freehand only suppresses this weed as a Pre-emergent herbicide.
• Envu Esplanade is registered as a pre-emergent herbicide for use around railroads, roadsides, industrial sites and utility corridors.

As it is an annual weed non selective contact options include Diquat and Glufosinate.

Systemic and long term residual non selective options include Glyphosate (Rapid Fire 800), Numchuk Quad and Cortex Duo.

If you use Glyphosate and water quality is an issue then we recommend the use of ProForce Manta Ray.