Black flag flower © Mariah Mustafa

Black Flag

Ferraria crispa

Quick facts

Status
Permitted s11
Life cycle
Perennial
Growth form
Geophyte
Origin
Southern Africa
Flowers
Purple/black, brown, cream or pale yellow.
Dispersal
Soil movement, water

Names

Other Common Names: Spider flower, Spider iris, Starfish lily, Flag lily, Spinekopblom.

Synonyms: ​​Ferraria undulata​.

Form and function

Illustration of entire black flag plant by Libby Sandiford
Ferraria crispa © Libby Sandiford

Grows up to 0.6 m tall. Plants generally survive fire, with underground corms remaining viable and enabling regeneration after burning. Reproductive maturity is reached in approximately two years, and seeds persist in the soil seedbank for around one year.

Flowers

  • Produces unusual, eye-catching flowers with a textured appearance.
  • Dark purple, maroon, brown, almost black, cream or pale yellow.
  • Often marked with stripes, blotches or speckles.
  • Petals have distinctive wavy, crinkled edges.
  • Flower centres are often darker than the surrounding petals.
  • Flowers are held above the foliage and have prominent, finely divided structures in the centre.
  • Flowers last for one day only.
  • Strong odour attracts flies for pollination.

Black flag flower © michelle__p

Leaves

  • Long, sword‑shaped leaves with a strong midrib
  • Grows up to 10cm long and up to 1cm wide.
  • Leaves are numerous and densely arranged, covering most of the stem.
  • Bluish/green glaucous leaves.

Black flag leaves © Michel Serjeant

Seeds

  • Black flag can produce thousands of seed per plant in late spring. 
  • Capsule (ellipsoid in shape).

Roots

  • Underground corm rounded to slightly flattened (2 to 4 cm in diameter).
  • Corm covered with papery fibres from old leaf bases.
  • Has a perennial corm and new season corms are added to a column of corms from previous years.
  • Produces offsets that remain attached to the parent corm.

Black flag corm © Michel Serjeant

Habitat

Prefers grey sandy soils, loam and limestone soils. Commonly found in coastal dunes, sandy flats, road verges and disturbed areas, particularly in banksia and tuart woodlands. It grows best in full sun and warm conditions and is not tolerant of frost.

Why is it a weed?

Once established in bushland it can form dense monocultures excluding most native flora.

History

First record of the plant was east of Perth in 1898 and has been around as a garden escape in Perth since the early 1900’s and has now naturalised from Perth to Busselton. 

How to control

Arum Lily

Physical

Arum Lily

Chemical

Arum Lily

Managerial

Physical

Hand removal/pulling of small populations and small plants should only be done with shovels or trowels as considerable care is required to ensure that all corms in the column of corms are removed. Surrounding soil may need sifting to locate and remove all corms, as any remaining corms can regrow and produce new plants.  Disposal by deep burial or burning.  Seeds will be stimulated by the disturbance.

Chemical

​​Herbicides appear to target only the present and/or previous years corm, leaving the deeper corms unharmed.  Its not translocated between corms.  Black flag is particularly challenging to manage with herbicide, any corm not affected by herbicide or dislodged corms will sprout and form a new plant the following year.

For dense flowering infestations/plants, apply a mix of 10g 2,2 DPA (740g/kg) and 2.5mL of a surfactant with 1L of water, using a foliar application method, ensuring full leaf coverage and spraying until just wet.

​For degraded sites, apply a mix of 150mL glyphosate (450g/L), 0.2g of metsulfuron methyl (600g/kg) and 15mL of a surfactant with 15L of water, using a foliar application method, ensuring full leaf coverage and spraying until just wet.

Managerial

Black flag is commonly found on disturbed edges of bushland and along roadsides.  It prefers full sun therefore increasing native species to reduce open canopy will reduce opportunity for black flag.

Further
reading

Minor use permits
external link PER96570 - Glyphosate
external link PER96598 - Metsulfuron-Methyl

Weed Distribution Map

LSID number: [2905672] | full LSID: [https://id.biodiversity.org.au/node/apni/2905672] | field_lsid: [] | taxon: [Ferraria crispa]

ALA Reference

References

  • Atlas of Living Australia. (n.d.) Ferraria crispa Burm. Atlas of Living Australia.
  • Brown, K., & Brooks, K. J. (2003) Bushland weeds: a practical guide to their management With case studies from the Swan Coastal Plain and beyond. Environmental Weeds Action Network
  • Brown, K. and Bettink, K. (2010) Black Flag (Ferraria crispa Burm.) is a difficult to control and persistent invader of Banksia/Eucalypt Woodland in south-west Australia. Ecological Management & Restoration, 11: 228-230
  • City of Mandurah. (n.d.) Black Flag Ferraria crispa (Burm.) . City of Mandurah Environmental Weeds.
  • City of Stirling. (n.d.) Garden plants and bushland invaders. City of Stirling.
  • Ohlsen, D. (2017, June 16) Ferraria crispa subsp. crispa. VicFlora Flora of Victoria.
  • Pacific Bulb Society. (2024, December 16) Ferraria crispa. Pacific Bulb Society.
  • Urban Bushland Council WA. (n.d.) Black Flag. Urban Bushland Council WA.
  • Weeds of Australia. (n.d.) Ferraria crispa Burm. subsp. crispa. Weeds of Australia; Lucidcentral.
  • Western Australian Herbarium (1998–) Florabase—the Western Australian flora. Department of Biodiversity, Conservation and Attractions.

Life Cycle

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Notes
Dormant
Active Growth
Flowering
Fruiting
Regularly or most commonly
Occasionally, given suitable conditions

Management

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Notes
Physical
Chemical
Optimal
Potentially, but conditionally dependent
Last updated: October 2026