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Downy rose myrtle (Rhodomyrtus tomentosa)

Downy rose myrtle is an ornamental shrub with the capacity to form dense thickets and displace other vegetation where it becomes invasive. It is not known to be naturalised in Victoria, so prevention and early detection are important for Australian land managers.

Key facts

Type: Weed, shrub.

Native to: Southern China and Southeast Asia.

Established in: .

Other names: Hill guava, Rose myrtle.

Best time to act: Survey when flowers or ripe berries make plants easier to spot, and treat before fruits mature and can be dispersed.

Identification

  • An evergreen, densely branched shrub or small tree that can grow to about 3 metres and form thickets.
  • Its opposite, oval leaves are leathery, with three prominent lengthwise veins and a softly hairy underside.
  • Pink to magenta flowers have five petals and numerous conspicuous yellow stamens.
  • The round berries ripen to purple or dark purple and contain many small seeds.
  • Look-alike: It may be confused with other myrtaceous shrubs; check for the combination of opposite, three-veined leaves with hairy undersides and pink flowers with prominent yellow stamens.

Where it grows

It is not known to be naturalised in Victoria, but suitable habitats include open forest, especially pine forest, woodland, riparian and coastal vegetation, heath, grassland and wetland margins.

Why it matters

  • Where it establishes, it can form dense thickets or a monoculture in the shrub layer, displacing other vegetation and making access difficult.
  • Changes to vegetation composition and structure can reduce habitat value for fauna, although the fruits and thickets can also provide food and shelter for some animals.
  • In pasture, invasion can reduce carrying capacity; in pine forest, thickets can compete with trees and impede maintenance work.

How it spreads

  • Birds and mammals eat the fruits and disperse the seeds; blackbirds are among the birds reported as possible vectors.
  • The small seeds may be carried by frugivorous birds over long distances, potentially more than 1 kilometre.
  • Avoid moving fruit-bearing material or soil that may contain seeds from infested areas.

Control options

  • For small plants, hand-pull or dig them out, removing the roots and collecting fruit-bearing material for secure disposal.
  • For larger shrubs, use cut-and-paint or another approved treatment only when the herbicide product is registered for the site and method, and follow its label and local requirements.
  • Revisit treated areas and remove seedlings or regrowth before plants set fruit.
  • Check with the relevant state or territory biosecurity agency about local guidance and reporting suspected infestations.

Hygiene and washdown

  • Clean soil and plant material from vehicles, machinery, boots and tools before leaving an infested area, and dispose of collected fruit and plant material securely.
  • Avoid transporting soil or fruit-bearing material from areas where the plant is present.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Declared weed. Weeds Australia lists it as a declared weed in the NT under the Weeds Management Act 2001. Check the NT declared weeds list for its class and what it requires.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

Sources