Identification and Reproduction

Fern leaf yarrow (Achillea filipendulina) is a close relative of native common yarrow (Achillea millefolium) but with tightly bunched yellow flowers.

Identification:

• Perennial plant growing up to 1.5m tall.
• 
• Flowers are yellow and grow in tight clusters at the top up the stem up to 10cm across.
• Leaves are fern-like with toothed margins.
• Roots systems are shallow and rhizomatous allowing the plant to spread outwards.

Common tansy, a look alike of fern-leaf yarrow, has more button-like flowers.

Reproduction: 

Fern leaf yarrow spreads through seeds and rhizomes. 

Habitat & Ecology

Found in disturbed areas, meadows, pastures and roadsides. It thrives in full sun. 

Impacts

Ecological: 

Can outcompete native plants, reducing biodiversity.

Social: 

It is toxic to dogs, cats and horses.

Management

Prevention is a high priority for this plant. 

• When leaving an infested site make sure bur seeds are not attached to clothes, shoes, equipment, pets and vehicles. 
• Be cautious when purchasing wildflower seed mixes, especially if they are not locally produced. These can contain seeds of fern leaf yarrow and other invasive species.

Mechanical/Manual Control:

• Plants can be dug up although care must be taken to remove the entire root system. Plants can regrow from root segments left behind. 
• Removal must go down 30 cm into the soil to remove all roots. 

Chemical Control:

• Dicamba, chlorsulfuron, clopyralid, MCPA, tricloplyr and 2,4-D are all reported to be effective in controlling fern-leaf yarrow.

Resources

Fern-leaf Yarrow Factsheet: Sea to Sky Invasive Species Council