Little Ironweed (Cyanthillium cinereum).
Little Ironweed (Cyanthillium cinereum) is also known as Purple Fleabane. It is is a fast growing, erect annual or biennial weed, which can become a perennial, and is in the sunflower family. It produces arrays of flat-topped flower heads. Each of these has pink to purple disc florets but no ray florets.
Purple Fleabane is native to tropical Africa and Asia, and is naturalized in Australia.
Apart from being rapid growing and forming dense patches in lawns, it is often a host for root-knot nematodes, and can act as a reservoir hosts.
The seeds of Little Ironweed produce a fatty oil, that is in use as an anthelmintic and alexipharmic. The oil is said to be effective against roundworms and threadworms.
People also use this for diarrhoea, coughs, to stop smoking, asthma, Parkinson’s disease and leprosy. It contains alkaloids, carbohydrates, saponins and phenolic compounds.
The distribution map for Little Ironweed is courtesy of The Atlas of Living Australia.
After you read this, you will be able to:
- Identify Little Ironweed or Purple Fleabane.
- Know the habitat of Little Ironweed or Purple Fleabane.
- Know the best cultural and chemical options for Little Ironweed or Cyanthillium cinereum.
How to Identify Little Ironweed.
Photosynthetic Pathway: C3 weed.
Category: Annual Broadleaf (Dicot)
Flower: The purple to pink flower heads of Little Ironweed contain 20 to 30 flowers. These are around 5 mm long. The flowers pollinate by wind, and in the right conditions it produces flowers and seeds for several months.
Height: Little Ironweed is up to 120 cm tall.
Leaf length: The leaves are alternate, and 3 to 4 cm long.
Leaf width: The leaves are 1.5 to 3 cm wide.
Reproduction: Little Ironweed mainly spreads by seeds. However, it also spreads vegetatively via stem segments if they break off, and come in contact with the soil. The seeds germinate in 8 to 33 days.
Comments: Wooly hairs cover the leaves, stems, and petioles of Little Ironweed. It has a dense, fibrous taproot that is about 3 mm thick, and it also has rhizomes. The stem is solid and not hollow.
Habitat: Little Ironweed forms dense patches in gardens, roadsides, waste ground and pastures. It grows in a soil pH range of 4 to 6, prefers sandy-loam soils. It also tolerates semi arid and partially saline soils.
For more information on weeds, check out our weed ID Chart.
How to Control Little Ironweed.
As its name suggests control of Little Ironweed is not easy. You can control Purple Fleabane by cultural and chemical means, but you can best manage this weed with an integrated approach.
Cultural control of Little Ironweed.
If you don’t manage Purple Fleabane it can quickly spread and out-compete existing vegetation.
- One of the best ways to prevent Little Ironweed or Purple Fleabane in turf, is to maintain a competitive stand of grass. This means fertilize properly, mow at the right height of cut for the grass type present and irrigate appropriately.
- Regular mowing can help manage this weed and this should happen before it flowers. Be aware though that the weed will keep regenerating from the roots.
- Due to its dense fibrous taproots and rhizomes, it is nearly impossible to successfully hand pull Little Ironweed. If you leave any part of the root behind this weed regrows.
Chemical control of Little Ironweed.
Little Ironweed (Cyanthillium cinereum) takes 12 to 18 months to control. This is due to the long term viability of the seeds.
Selective Control of Little Ironweed.
Herbicides that contain the actives Dicamba (Casper Herbicide, Contra M), 2,4-D, and Triclopyr have been investigated for Tall Ironweed control.
- Dicamba alone resulted in only ≤76% control of Tall Ironweed, and also showed >81% regrowth.
- Triclopyr alone or Triclopyr plus 2,4-D result in >91% control.
- Triclopyr alone or with 2,4-D result in less than 39% regrowth.
Remember you cannot use dicamba on Buffalo grass.
Non Selective Control of Little Ironweed.
Non selective Glyphosate applications result in variable to excellent levels of Little Ironweed control. In a study by Peters and Lowance (1979) Purple Fleabane control was reported to range from 2% to 88%.
These products kill all vegetation, and in the case of Numchuk, Renegade and Cortex Duo have a long term residual to prevent any regrowth or Purple Fleabane.
- Renegade. This stops germinating weeds for up to 12 months, and reduces the need for multiple herbicide applications.
- Numchuk Quad. Gives effective post and pre emergence weed control for up to 12 months.
- Cortex Duo. Gives a rapid knockdown and residual control for up to 3 months. Safe to use around trees.
- Rapid Fire 800. If you use Glyphosate and water quality is an issue then add Manta Ray spray adjuvant and pH buffer to your tank mix.
