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Tangled hypericum (Hypericum triquetrifolium)

Tangled hypericum is an introduced Mediterranean herb recorded in Australia and can be confused with the better-known St John's wort. Accurate identification helps land managers target control and avoid spreading this weed.

Key facts

Type: Weed, herb.

Native to: Mediterranean region.

Established in: VIC.

Other names: Wavyleaf St John's wort, Wavy-leaved St John's wort.

Best time to act: Inspect when the yellow flowers make plants easier to spot, and treat before seed capsules mature.

Identification

  • It is an upright, branching herb with opposite leaves.
  • The leaves have undulating margins and are not conspicuously dotted with translucent oil glands.
  • It produces yellow flowers with five petals in clusters near the ends of stems.
  • Check the whole plant and its leaf characters, as yellow flowers alone are not enough for identification.
  • Look-alike: Compared with St John's wort (Hypericum perforatum), tangled hypericum lacks conspicuous translucent oil-gland dots on its leaves and has wavy, non-recurved leaf margins.
  • Look-alike: Native Hypericum species lack black gland dots on the petals and leaves; they also have four longitudinal stem ridges and stamens that are not fused into bundles.

Where it grows

In Australia it may occur in disturbed ground such as roadsides, waste areas and pasture, where it can mix with other vegetation.

Why it matters

  • It can establish in disturbed sites and compete with desirable pasture or native vegetation.
  • Its resemblance to St John's wort can make identification and targeted management more difficult.
  • Seed-bearing plants can contribute to further infestations if moved with soil, machinery or plant material.

How it spreads

  • Seeds can be spread when contaminated soil or plant material is moved.
  • Vehicles and machinery can carry contaminated material between sites.

Control options

  • For small patches, hand-pull or dig out plants before they set seed, and collect and contain seed-bearing material.
  • For larger infestations, use only herbicides registered for the species and site, or other approved methods, following the label and local advice.
  • Revisit treated areas to check for surviving plants and new seedlings, and treat them before they set seed.
  • Check current local requirements and report suspected infestations to the relevant state or territory biosecurity agency where appropriate.

Hygiene and washdown

  • Clean soil and plant material from vehicles, machinery, boots and gear before leaving an infested site.
  • Avoid moving contaminated soil or seed-bearing plant material, including in fodder.
  • 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: State prohibited weed. State prohibited weeds are the highest priority: the Victorian Government is responsible for eradicating them, so report any sighting to Agriculture Victoria.
  • 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: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • 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.

  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria

Sources