Carrot Weed (Cotula australis)
After you read this, you will be able to:
- Identify Carrot Weed, Annual Buttonweed or Bachelor’s button.
- Know what conditions favour Annual Buttonweed.
- Know the best cultural and chemical options to control Carrot Weed.
Why is Carrot Weed a Problem Weed?
- It is very competitive and quickly establishes in disturbed areas, outcompeting other plants.
- It is very unsightly in lawns and gardens.
- Because of its rapid growth and seed production it is difficult to control.
Table Showing Differences Between Common Carrot Leaf Weeds.
Weed | Roots | Flowers | Smell when crush | Spiny Burrs |
Carrot Weed | Weak taproot | Pale Yellow with no petals | No | No |
Bindii | Fibrous | Green | No | Yes |
Swinecress | Strong taproot | Green | Yes | No |
- Carrot Weed is often confused with Bindii and Swinecress because of its much divided (carrot-like) hairy leaves.
- Swinecress has a skunk-like smell whereas Bachelor’s Button has no odour.
- Carrot weed produces pale yellow flowers on the end of stalks in early Winter. Bindii flowers much later, and has no flower stalks.
Carrot Weed Lifecycle.
- Germinates in the Spring or Autumn.
- Grows rapidly.
- Flowers late Winter to Spring.
- Dies back over summer.
Over Autumn and Spring, the seed germinates and then quickly grows. From late Winter to Spring, the plant produces flower stems, and then flowers. As Summer closes in, annual plants usually die or the top growth dies if they are perennials.
Bachelor’s Button is a prostrate, low-growing weed, although it can grow up to 12 cm tall.
The flower heads are button-like and yellow or white with no ‘petals’. From Spring to Autumn the flowers are on slender stalks.
How to Identify Carrot weed.
How to Remove Carrot weed from your lawn.
Cultural and chemical options control Carrot Weed, Cotula, Bachelor’s Button or Annual Buttonweed. Autumn is an ideal time carry out control of this perennial weed.
Cultural Control of Carrot Weed.
- If Bachelor’s Button isn’t a major problem, you can remove it by hand. However, you need to remove all of the root system to prevent regrowth.
- Cotula favours damp, moist soils. So deal with any drainage issues and don’t over water.
- If the soil is compact, carry out a soil aeration programme. This allows air exchange, and helps excess water move out of the rootzone.
- Feed your turf and use the right turf fertilizer. A thick turf cover that makes it difficult for Carrot Weed to compete.
- Make sure that you mow at the right height, as this helps favour turf grass over this weed.
Chemical Control of Carrot Weed.
Pre-Emergent Control of Carrot Weed.
- Envu Esplanade is registered in Australia for Buttonweed, and Envu Specticle in the US.
- In the USA, Isoxaben is recommended prior to germination, followed by 12 mm of irrigation.
Post Emergent Control of Carrot Weed
- 2,4-D
- Clopyralid
- Dicamba
- Duke 100WG Herbicide and
- Rimsulfuron
Interestingly, Casper Turf Herbicide is labelled for Carrot Weed in South Africa at 800 g to 1 Kg/Ha but not in Australia.
Table of Post Emergent Carrot Weed Herbicide Rates.
Product | Active | Chemical Group | Rate/Ha | Comments | ||||
Casper | Prosulfuron + Dicamba | 2 and 4 | 800g-1Kg | Apply from Autumn to Spring. Use high rates in cool months or if high weed pressure. Control takes 4 to 6 weeks. Use an NIS at a rate of 0.25 to 0.5% v/v. | ||||
2,4-D | 2,4-D | 4 | 1.8-3.2 | Wet foliage thoroughly. DO NOT mow lawn for 1 week before and at least 1 weed after application. DO NOT use on Buffalo grass (WA only). | ||||
Duke | Iodosulfuron | 2 | 100g | Always use an NIS or Overtake Oil. Use in 200-500 L/ha water. | ||||
Dicamba | Dicamba | 4 | 1.2L + 3.2L of 2,4-D Amine 625g/L | Use a minimum of 1000L/Ha water. Do not spray on Buffalo or Bent Grass. | ||||
Warhead | MCPA + Clopyralid + Diflufenican | 4 + 12 | 5 L | You may see discolouration on kikuyu, carpet grass and Queensland blue. Avoid overlapping. Use an NIS. | ||||
Non Selective Control of Carrot Weed.
Non selective options for Carrot Weed include Glyphosate (Rapid Fire 800).
If you use Glyphosate and water quality is an issue then we recommend the use of ProForce Manta Ray.
In Conclusion.
A native weed, Carrot Weed favours moist soils. So the first step to manage this weed is to identify any drainage issues. The second step, before you apply any weed killer, is to maintain a healthy turf surface.
