The Problem with Mimosa Pigra
Mimosa pigra is a much–branched, thorny legume shrub that grows along waterways and invades freshwater wetlands and swamps. Originally from Central and South America, it was planted at the Darwin Botanic Gardens in the late 1800’s as a curiosity. Its invasive nature was not realised until the 1950’s when it was observed growing in drainage lines and creeks.
It forms dense, impenetrable thickets, 3-6 meters high. If left untreated Mimosa pigra has the ability to restrict access to water impacting on recreational activities, tourism, stock watering points, pasture quality and mustering.
The Northern Territory has the most extensive infestation of Mimosa pigra, which covers an approximate area of 80,000 ha. In 2001 a local landholder discovered Mimosa pigra growing at Lake Proserpine (Peter Faust Dam). This infestation is one of only two infestations found outside of the Northern Territory, the other being on the Western Australian/Northern Territory Border.
Mimosa pigra is spread via water, contaminated soil, vehicles, boats, boat trailers, animals and through suckering.
This species is a Weed Of National Significance and is also Restricted Matter – Category 5 under the Biosecurity Act 2014. This means that it cannot be kept.
The Mimosa Pigra Plant
- Flowers are light pink, round and fluffy balls generally 1-2 cm across.
- Each leaf is approximately 25cm long and has up to 16 opposite segments, which consists of segments 5cm long made up of opposite pairs of leaflets. These leaflets fold up when touched or at night.
- The thorns of Mimosa pigra resemble those found on a rose bush however on Mimosa pigra these thorns are much more numerous.
- The seeds are oblong approximately 4-5 mm by 2 mm in size encased in a brown hairy segmented pod 6-8 cm in length.
- Mimosa pigra seeds have an average seed life of 22 years.
- Drewry. J, Higham W, Mitchell. C 2008, Water Quality Improvement Plan: Final report for Mackay Whitsunday region, Mackay Whitsunday Natural Resource Management Group
- The State of Queensland, Department of Environment and Resource Management 2011, REED Regional Ecosystem Description Database