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Thalia geniculata (MARANTACEAE) Fireflag, Arrowroot, Bent Alligatorflag

Image: Habit

Thalia
Photo: Sheldon Navie

Since it was first found growing in a drain in Toowong last year, this plant has popped up in several new locations around Brisbane including in Ithaca Creek and Enoggera Creek.

Thalia is an aquatic, upright, emergent perennial with 1m long arrow shaped leaves on thin stems. It forms dense clumps to 3m tall and has the potential to become another environmental weed which will choke waterways and exclude habitat for native fauna.

Image: Foliage and flowers


Thalia
Photo: Sheldon Navie

Thalia can be easily identified by its attractive purple and white flowers, which are borne on ‘zig-zagged’ stalks at the top of the stems.

Image: Flowers and Fruit


Thalia
Photo: Sheldon Navie

It flowers and fruits through summer and autumn and can spread through vegetative clumping and seed dispersal along waterways.

Image: Fruit


Thalia
Photo: Sheldon Navie

If you find Thalia in your waterway, report it to local council. It can be treated effectively by cutting and painting with Roundup biactive, which is registered for use in a waterway.