Across our local wetlands, weedy Watsonia is smothering the native vegetation and changing wildlife habitat but specialist contractors are out there dealing it a heavy blow. 

The colourful flowers and broad strappy leaves of Watsonia are well known to many people but few appreciate how far into our beautiful wetlands this weed has penetrated. Forming dense stands around water courses, Watsonia out-competes and smothers native vegetation. After flowering has finished, the plant dies back to a tuber-like corm in late spring, leaving the foliage to die off and dry. The corm remains dormant for the hot, dry months while the dry leaves considerably increase summer fuel loads for bushfires. The corms are safe underground and are unaffected by most fires. They are a key part of Watsonia’s success in invading the wetlands. Plants grow in densely crowded stands and their corms often grow together in large tight clusters, forming extensive underground barriers that lock out the root systems of native shrubs. Hence the corms allow the Watsonia to survive the hot, dry bushfire seasons while preventing native shrubs from growing in the cooler wet months.   

Sadly, Watsonia is now widespread across the Peel-Yalgorup wetland system. It found its way to the islands of the Murray River delta many years ago, forming large dense stands across most islands. Much of the natural vegetation here has succumbed to the slow smothering spread of these foreign invaders. However work in past years has slowed the spread on the islands, and on one – Jeegarnyeejip Island – only scattered patches of Watsonia remain.  Left untreated, these patches would eventually spread again to re-establish the original cover across the island but work carried out with the Shire of Murray has “mopped up” these persistent patches of Watsonia. The entire island was checked on foot and surviving clumps treated. This process is tedious and must be thorough to ensure even the smallest plants hidden under bushes and clumps of grass aren’t overlooked. Follow-up treatment of Watsonia – as with most weeds – can take many years to be fully effective but it’s hoped that only minimal control will need to be done here in the future. The Shire of Murray and its partners have recently carried out revegetation work on the island to fill some of the gaps and fast-track the natural process of regeneration.    

Elsewhere in the Peel-Yalgorup wetlands, PHCC’s Wetland Restoration Officer Mike Griffiths has been busy with staff from DBCA inspecting areas for Watsonia and other weeds. Work is due to take place in the current growing season to control Watsonia, Cape Tulip and Pink Gladiolus on the south-west shores of the Harvey Estuary. Here, these weeds grow together in mixed patches and have started to penetrate the stands of paperbark and rush beds. Mike has also been talking to land owners about Watsonia and related weeds on properties adjoining Ramsar wetland sites where broader environmental works have been carried out. Several owners have expressed interest in undertaking weed management and it is hoped that more control of Watsonia can be done under Landholder Works Agreements in identified priority areas next year to build on current and past control work.  All of this gives hope that we and our partners can slow the relentless spread of Watsonia in our wetlands and give our unique flora and fauna some breathing space.  

This project is a partnership between PHCC and the Shire of Murray with funding from the Australian Government’s National Landcare Program

We acknowledge the Noongar people as Traditional Custodians of this land and pay our respects to all Elders past and present