Quick Facts

Quick facts

  • Tangled Hypericum (Hypericum triquetrifolium) is native to the eastern Mediterranean region.
  • It is a widely branched, usually pyramid shaped herb to about 50 cm high with yellow flowers.
  • It is a weed of orchards, vineyards and field crops in Tunisia, Lebanon, Turkey and Greece.
  • In Australia, it is only known to have naturalised in a small part of central Victoria in an oat crop and adjacent woodland.
  • Application of a suitable herbicide is the most effective control method for Tangled Hypericum.

What Does It Look Like?

What is it?

Tangled Hypericum (Hypericum triquetrifolium) is a widely branched, usually pyramid-shaped herb growing to about 50 cm high which produces shoots from lateral roots or rhizomes (underground stems). The tangled stems are hairless and often bear numerous small black glands. The leaves are arranged on the stems in opposite pairs. They are stalkless, narrowly triangular to oval, 3–20 mm long, 1–9 mm wide, and usually bear black glands close to the wavy margins. 

The flowers are borne near the ends of slender side branches in broad, open, leafy 'sprays' (panicles). Individual flowers are 8–14 mm wide with five yellow petals and numerous stamens (pollen bearing stalks) united into three bundles.

The dry fruit is 3–5 mm long, 2–3.5 mm wide and splits open to shed the seeds. The seeds are darkish brown, more or less cylindrical and 1.5–1.8 mm long (Willis 1972; Parsons & Cuthbertson 1992; Walsh 1996; Robson 2002).

For further information and assistance with identification of Tangled Hypericum, contact the herbarium in your state or territory.

Flower colour


Growth form (weed type/habit)


Where it currently grows? Preferred habitat

At Tarnagulla in Victoria, Tangled Hypericum has been recorded as occurring in an oat crop and adjacent native woodland (Walsh 1996; National Herbarium of Victoria 2008). In the Mediterranean region, its habitat is recorded as stony ground and cultivated fields. It is a weed of orchards, vineyards and crops in Tunisia, Lebanon, Turkey and Greece (Parsons & Cuthbertson 1992; Robson 2002).

Are there similar species?

In south-east Australia, Tangled Hypericum is most likely to be mistaken for its weedy close relative St. John's Wort. The main stems of Tangled Hypericum are widely branched for most of their length, resulting in a broad pyramid shape. St. John's Wort has main stems that are less branched in the lower half, with branching that is more upright than Tangled Hypericum. The leaves of Tangled Hypericum have wavy margins while the leaves of St. John's Wort usually have the margins recurved (turned downwards) but they are never wavy (Robson 1980; Robson 2002).

Where confusion exists over the correct identification of plants, please contact the herbarium in your state or territory.

Why Is It A Weed?

What are its impacts?

Native ecosystems: Tangled Hypericum may compete with and eliminate other vegetation.

Agriculture: It is possibly poisonous to stock and may cause photosensitisation, a condition which causes light coloured animals to become sensitive to sunlight, but neither of these impacts have been confirmed (Parsons 1973, Carr et al. 1992, Parsons & Cuthbertson 1992, Walsh 1996). Other alleged toxic effects on grazing animals have been reported overseas, including eczema, blindness, gastroenteritis and death (Robson 1980).

How does it spread?

Tangled Hypericum seed is spread as contaminants of agricultural produce, vehicles, farm machinery, water, mud and fodder. Tangled Hypericum may also be spread by cultivation equipment when pieces of lateral root or rhizome are broken from existing plants and spread to new sites where they can produce new plants vegetatively (Parsons & Cuthbertson 1992).

What is its history in Australia?

The earliest, presumably naturalised, record of Tangled Hypericum in Australia is a 1908 collection from Eldorado in north-eastern Victoria. All other Australian wild collections are from a single patch of about 2 ha at Tarnagulla in central Victoria. It is believed to have occurred at this site since1910 but the only, and therefore earliest, specimens with collection dates are from November 1965. In 1969 it appeared to be spreading at the Tarnagulla site and it was proclaimed a noxious weed in Victoria (Parsons & Cuthbertson 1992; National Herbarium of Victoria 2008).

How To Manage It?

Best practice management

If you find this weed in Victoria you should not attempt to control the plant but instead contact authorities (see https://agriculture.vic.gov.au/biosecurity/weeds/state-prohibited-weeds/tangled-hypericum)

Non-chemical control: Manual control: Using cultivation as a control method is discouraged for Tangled Hypericum because it is likely to result in the spread of broken root pieces from infested to clean areas.

Chemical control: Spraying with a suitable herbicide is reasonably effective if applied to the plants when they are actively growing but repeat sprayings are necessary to kill regrowth (Parsons & Cuthbertson 1992).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

The seeds of Tangled Hypericum germinate in autumn. Roots grow rapidly in winter and above ground growth occurs in spring. Flowers and fruits are produced in summer. Above ground parts die off in autumn and are replaced by new growth from root crowns and rhizomes in winter and spring (Parsons & Cuthbertson 1992).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

There have been no collections of Tangled Hypericum from Eldorado, Victoria, since the original record in 1908. Therefore, it may no longer be present at that site. All other Australian naturalised records are from Tarnagulla, Victoria. It was reported as still persisting at the Tarnagulla site up until 1992 despite regular treatment, presumably with herbicide, but no records substantiated by specimens exist from beyond 1965. It is not known if it still persists at that site (Parsons & Cuthbertson 1992; National Herbarium of Victoria 2008; Reid 2008 pers. obs.).

Where does it originate?

Tangled Hypericum is native to the eastern Mediterranean region including Greece, Turkey, Egypt, Lebanon, Syria, Iraq and Iran. It is introduced to the Mediterranean region west of Sicily including Italy, France, Spain, Algeria and Tunisia (Walsh 1996; Robson 2002).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Hypericum triquetrifolium

Other scientific names (synonyms)?


Does it have other known common name(s)?

Curled-leaf St. John's Wort, Wavyleaf St.John's Wort, Wavy-leaf St. John's Wort

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