Type of plant
Bulbs or Corms
About this weed
Black Flag is a perennial cormous herb that dies back over summer but sprouts again during winter. Originally from South Africa it was introduced as a garden plant grown for its unusual black flowers which individually last only one day. The flowers produce a strong odour. Each year the plant produces a large number of corms (up to 20 corms) before dying back over summer. The weed often produces large clumps of fleshy foliage and strappy leaves which are easily identifiable.
This weed is a malodorous, cormous perennial growing to 0.6 m high. Flowers last for one day only and are pollinated by flies. Flowers produce a strong pungent scent. Generally Black Flag survives fire.
Impact on Bushland
If left will spread bushland and may compete with native plant communities. Each year plants produce new corms that are added to a column of dormant corms produced in previous years. There can be 15-20 corms in a single column.
Occurs on the Swan Coastal Plain and through various areas in the South-West Province. It prefers road verges, dunes and wasteland sites.
Priority for removal
High: major threat to the conservation values of Banksia woodlands and South-West Province.
Remove very small populations in degraded sites. Sift soil to find all corms.
Spray 2,2 DPA 10 g/L + Pulse when flowering. In degraded sites try glyphosate 1% + metsulfuron methyl 0.2 g/15 L + Pulse. It takes a number of years to control populations. Read the manufacturers’ labels and material safety data sheets before using herbicides. Optimum treatment is in August and September.
August, September, October
Purple, Black, Brown
Hussey, B.M.J., Keighery, G.J., Dodd, J., Lloyd, S.G. and Cousens, R.D. (2007) Western weeds. A guide to the weeds of Western Australia, Second Edition, The Weeds Society of Western Australia, Victoria Park, Western Australia.