St john’s wort weed

St. John’s Wort

St. John’s Wort Plant

A landscape workhorse, St. John’s wort is a champion at providing food and shelter to wildlife—especially pollinators—as well as adding blossoms, colorful foliage, and great texture to entry gardens, foundation plantings, perennial beds, and mixed shrub borders. This North American native all-star shrub is easy to grow and a cinch to incorporate into almost any landscape. You’re sure to delight in its sunny yellow flowers in summer and low-maintenance habit year-round. Seldom browsed by deer and rabbits, it is a great plant for landscape plagued by these munching pests.

genus name
  • Hypericum spp.
light
  • Part Sun,
  • Sun
plant type
  • Shrub
height
  • 1 to 3 feet,
  • 3 to 8 feet
width
  • 12-48 inches wide
flower color
  • Yellow
season features
  • Summer Bloom
problem solvers
  • Deer Resistant,
  • Drought Tolerant
special features
  • Low Maintenance,
  • Attracts Birds,
  • Cut Flowers
zones
  • 3,
  • 4,
  • 5,
  • 6,
  • 7,
  • 8,
  • 9
propagation
  • Layering,
  • Stem Cuttings

Where to Plant

St. John’s wort thrives in full sun to part shade and moist, well-drained soil. It is tolerant of a wide range of soil types, including slow-draining clay. Shrubs growing in partly shaded sites will have fewer blossoms than shrubs planted in full sun. In areas with wet winters, St. John’s wort can be short-lived. If wet winters are a challenge in your area, plant St. John’s wort in well-drained, sandy soil.

Check out this information on well-drained soil.

St. John’s Wort Care Must-Knows

Plant St. John’s wort in spring or early summer. Blanket soil around plants with a 2-inch-thick layer of mulch and water plants regularly during the first growing season to encourage an extensive root system. Reduce watering during the second growing season.

In some climates the tips of St. John’s wort branches die back in winter. Simply shear the plants back to live wood in spring and this hardy perennial will regrow. St. John’s wort blooms on new growth so winter dieback is not a problem. Prune plants as needed in early spring and they will produce a large crop of flowers in summer. Every three or four years, consider renewal pruning St. John’s wort. Renewal pruning involves shearing the plant back to half its height in spring. Renewal pruning encourages dense, vibrant new growth and helps the plant retain a pleasing, rounded form.

Keep your shrubs in shape using these pruning techniques.

More Varieties of St. John’s Wort

‘Ignite Red’ hypericum

Hypericum androsaemum ‘Seiball’ begins blooming with large yellow flowers in late spring and continues to bloom through fall. By midsummer, bright orange-red berries adorn the plant, becoming more profuse as the season progresses. Cut stems with berries for use in cut-flower arrangements. This rust-resistant plant grows 12-36 inches tall and wide. Zones 5-8

St. John’s wort

Hypericum perforatum is a shrubby perennial with bright yellow blooms and green leaves, often edged in red during cool weather. This species is used as an herbal supplement, but because it can cause interaction with other drugs, consult your doctor before ingesting it. The plant grows 1-3 feet tall, making an attractive groundcover when planted en masse. Zones 3-8

‘Sunny Boulevard’ hypericum

Hypericum kalmianum ‘Deppe’ bears loads of sunny yellow blooms from early through late summer. In fall, it develops dull red berries that persist through winter. Deer avoid this heat-tolerant shrub. It grows 2-3 feet tall and wide. Zones 4-8

St. John’s wort: pest

Form: herbaceous — perennial

Status: present in WA

Appearance

Native of Europe, western Asia and North Africa. There are two varieties, var. perforatum with broad leaves and var. angustifolium with narrow leaves, but intermediates are also known. One plant will produce thousands of seeds and these may remain viable in the soil for many years. Introduced to Australia in 1800s, and still spreading, especially on roadsides and cleared land. St. John’s wort can densely infest grazing land, particularly when pastures get denuded.

The leaves of St. John’s wort contain a toxin which causes photosensitisation, especially amongst white-faced stock. The plant also affects animals nervous systems, causing unthriftiness and sometimes death.

St John’s wort is a perennial plant that reproduces from seed and from creeping underground rhizomes. The plants do not flower in their first year, but flower and seed prolifically in later years. Seeds may survive in the soil up to six years before germination.

Stems: In winter the stems are spindly and low growing with a dense mat of leaves. Erect woody stems are produced in spring. These are cylindrical and shiny, often reddish, 0.6 to one metre tall, branching near the top with two opposite ridges running down the stem.

Leaves: 1.5 to 3 centimetres long and narrow, stalkless and arranged in opposite pairs. They bear translucent oil glands, which are clearly seen when held to the light.

Flowers: The flowers are up to 25 millimetres across with five bright yellow pointed petals, that often have black dots on the edges. There are three bundles of yellow stamens in each flower. Numerous flowers are found together in clusters near the top of the stems. Flowers in late spring and summer

Seeds: Dark brown to black, cylindrical and one millimetre long. They are produced in large numbers in a sticky capsule. Seeds germinate in either spring or autumn.

Agricultural and economic impact

Toxic to livestock.

Declared pest category

The Western Australian Organism List (WAOL) contains information on the area(s) in which this pest is declared and the control and keeping categories to which it has been assigned in Western Australia (WA). Use the external links on this page to reach St. John’s wort in WAOL.

Search > detect > record

Record: this pest using the MyWeedWatcher smartphone and tablet application or online recording tool.

Control method

When using any agricultural chemicals please ensure that you always follow instructions on the label and any permit. Users of agricultural chemical products must always strictly comply with the directions on the label and the conditions of any permit.

Only registered products can be used for weed and pest control.

Control methods for this plant can be found through the APVMA website, use “wort” as the pest name.

St John’s wort

Common and botanical names

St John’s wort

Hypericum perforatum L. Family Clusiaceae

Origin and distribution

Figure 1. distribution of St. John’s Wort in Victoria.

Native to Europe, Asia and North Africa, St. John’s wort first became a problem in Victoria near Bright, late in the 19th century. It was widespread in North East Victoria by 1905.

St. John’s wort is found through much of Victoria with the most severe infestations in the North East. It invades grasslands, woodlands, open forest, pastures, forestry plantations, roadsides, railway lines and river banks.

Description

Perennial herb, usually about 80 cm high.

Stems – non-flowering stems to about 30 cm long grow from the crown in autumn and winter and form tangled thickets (Figure 5). Erect, woody, flowering stems to 1.2 m produced from crown in spring, often reddish, with long ridges bearing dark glands. Young stems weakly two-ridged.

Figure 2. St John’s wort.Figure 3. Flowers

Leaves – in opposite pairs, 5-30 mm long, 1.5-5 mm wide, oval to linear, hairless, upper margin usually curved over, underside paler; distantly black-dotted or black dots confined to near apex; bearing numerous translucent oil glands visible when held to the light (Figure 4).

Flowers –2 cm diameter, in numerous terminal clusters (Figure 3). Five sepals, five petals; sepals 4-7 mm long, rarely with 1 or 2 black dots on margin; petals 2-3 times as long as sepals, golden yellow with black dots on the margins.

Fruit – a sticky, narrowly ovoid capsule, to 8 mm long.

Seeds – light to dark-brown or black, 1 mm long, cylindrical and pitted (covered with many indentations), germinate during autumn, winter and spring. A plant may produce up to 33,000 seeds per year.

Roots – stout, to 1 m deep in the soil, with woody, lateral rhizomes which grow horizontally, producing buds that form new aerial growth.

The problem

St John’s wort is extremely invasive and competes strongly with native vegetation and pasture. Well-established infestations can largely eliminate all other plants and restrict recruitment to the overstorey. Seed can remain dormant in soil for at least 20 years.

When eaten by livestock, St John’s wort causes photosensitisation of exposed skin (inflammation eg., of face, ears, lips), affects the nervous system of animals causing depression and hyperthermia (panting, salivation, respiratory distress) and alters heart, blood vessel and intestinal function. Chronic poisoning results in weight loss, reduced reproductive performance and death. Light-skinned and soft-skinned animals and those with white markings are the most affected. Those with thick, tough and pigmented skin are less affected. Early signs of clinical poisoning include agitation, pawing of the ground, rubbing of the head and face against fixed objects and mild diarrhoea.

Figure 4. Leaves showing translucent oil glands.

Hypericin in the oil glands of St John’s wort leaves and flowers is the cause of the toxicity, but the effects depend on activation by bright sunlight of the poison circulating in the bloodstream. Tolerance of any animal to the poison appears to be directly related to the amount of skin surface protection it has.

The minimum toxic dose of foliage for sheep is about 4% of live weight. Horses are more sensitive to hypericin than cattle and sheep, with goats the least sensitive. Recent studies indicate that Hereford cross cattle are two to three times more tolerant than Merino sheep. The amount of St John’s wort consumed to produce a toxic reaction is less when the plant is in flower or when animals graze the more toxic, narrow-leaved biotypes.

Affected animals generally recover after 3 to 6 weeks once removed from access to the plant, but sheep with early signs of poisoning typically recover within 12 hours if they are moved indoors. Poisoning can reduce milk yield, and cause abortions in animals. The plant is more toxic when in flower and may contain more than 50 times more hypericin in early summer than in late winter. Narrow-leaved forms of the plant can be twice as toxic as broad-leaved biotypes. Plants become markedly more poisonous when the flowering shoots have grown 5-10 cm high. Hay containing St John’s wort also causes poisoning.

The plant has a number of medicinal and pharmaceutical uses.

Similar species

Figure 5. Crown and upright flowering stems in autumnFigure 6. Flower bud, flower and young fruit

There are two native Hypericum species. Care should be taken to not confuse them with St John’s wort. The two natives have four-ridged stems, leaves that are generally less than 3.5 cm long and petals and anthers that lack black gland-dots.

There are also seven other introduced Hypericum species naturalised in Victoria including the noxious weeds tutsan (H. andosaemum), St Peter’s wort (H. tetrapterum) and tangled hypericum (H. triquetrifolium). St John’s wort is the only one with two-ridged stems, leaves less than 3.5 cm long that are curved under at the edges, conspicuous translucent oil glands, and black gland dots present on the petals and anthers but usually absent from the sepals.

Life cycle and reproduction

St John’s wort reproduces from crowns and roots and by seed. It generally does not flower in the first year of growth.

Dispersal

Seeds adhere to stock and other animals, and are carried in the digestive tract of animals. Seedlings have been observed in cattle dung. Seed spreads only short distances by wind, but can be carried long distances by water, machinery and animals. Rhizomes grow horizontally producing buds which form new crowns. Cultivation may spread pieces of rhizome which produce new plants.

Management

Figure 7. SeedsFlowering period

Prescribed measures for the control of noxious weeds

  • Application of a registered herbicide
  • Physical removal

Important information about prescribed measures for the control of noxious weeds.

Other management techniques

Changes in land use practices and spread prevention may also support Bathurst burr management after implementing the prescribed measures above.

Biological Control

Two species of beetle, first released in the 1930s, have established in Victoria: Chrysolina hyperici and C. quadrigemina. The adult beetles are bronzy black, dark-blue, or purple, about 6 mm long and oval in shape. The larvae are orange with dark heads and the eggs are orange. Both larvae and adults defoliate the weed. Larvae attack the winter growth and adults attack the spring growth. Within a few years at favourable sites the beetles reach densities which are high enough to cause completedefoliation. The beetles are effective in open, unshaded country in conjunction with improved pasture.

The St John’s wort gall midge Zeuxidiplosis giardi, first released in Australia in 1953, has red larvae which develop in circular galls on the leaves. It is generally ineffective but is most abundant in damp shaded situations

An aphis Aphis chloris, released in 1986-87, spread rapidly and is well established. It contributes to biological control of the weed however it only weakens plants for a short time. The St John’s wort aphis has no preference between sunny and shaded areas and is most commonly found on flowering stems in summer.

The St John’s wort mite Aculus hyperici, first released in 1991, has no preference between sunny or shaded areas. The mites stunt the growth of both rosettes and flowering stems, gradually weakening plants over a period of months and reducing vigour and seed production. The mite is invisible to the naked eye. It is present throughout the area infested by St John’s wort in Victoria and has a significant impact.

The crown and root boring beetle Agrilus hyperici was introduced many years ago but failed to persist in Victoria. Several native insects attack St John’s wort and may occasionally cause significant damage.

Biological control is a long term program, best used on large, chronic infestations with a low priority for control due to inaccessibility, remoteness or low threat of spread.

Further advice

  • Contact your local landcare or friends group for further assistance and advice.
  • Call the DEPI Customer Service Centre on 136 186.
  • Visit the Weeds Australia website at: http//www.weeds.org.au

Muyt, A. (2001) Bush Invaders of South-east Australia. Meredith, Vic., R.G. & F.J.Richardson.

Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious Weeds of Australia. Melbourne, Inkata Press.

St. John’s wort (Hypericum perforatum)

St John’s wort is a herb with bright yellow flowers. It can poison livestock.

Profile

How does this weed affect you?

St John’s wort:

  • competes with pastures
  • poisons livestock
  • can downgrade wool with ‘vegetable fault’
  • can reduce property value.

Livestock poisoning

St John’s wort contains a chemical called hypericin. Livestock that eat it become very sensitive to sunlight. Stock will only eat St John’s wort when other feed is scarce. Minor exposure to St John’s wort affects animal health as:

  • weight loss
  • fewer pregnancies
  • stillbirths
  • weak young
  • cows producing less milk
  • fewer lambs and calves surviving weaning.

Intense sunlight worsens the effects of hypericin. Access to shade helps protect animals. On sunny days, stock without access to shade can develop signs of acute poisoning in five hours.

Early symptoms of acute hypericin poisoning include:

  • agitation
  • rubbing the head against posts or trees
  • weak hind legs
  • panting
  • confusion
  • depression.

Some animals develop mild diarrhoea.

As poisoning gets worse, animals get a high temperature. The skin around their forehead, eyes and ears swells and turns red. Head rubbing against hard objects causes wounds and bleeding. Animals can die from acute hypericin poisoning.

Tolerance

Age and the amount of skin protection affect how tolerant animals are to hypericin. More tolerant animals have:

  • pigmented skin
  • dense wool or hair
  • thick, tough skin.

Adults are more tolerant than young animals because they have thicker skin, wool or hair. Suckling young can ingest hypericin from their mother’s milk.

Keep affected stock in full shade for 4 to 7 days. Animals should not show further signs of poisoning when returned to sunlight. If they do, they haven’t excreted all the hypericin from their blood yet and need to go back into the shade.

Keep pregnant and lactating animals out of St John’s wort-infested pastures. Provide shade in infested paddocks to improve stock tolerance to hypericin.

Never graze when St John’s wort is flowering. Levels of hypericin change over the growing season. Hypericin levels:

  • are lowest from July to August
  • rise rapidly in spring when flower shoots are taller 5 – 10 cm
  • continue rising as flowers develop
  • are strongest when the plant is in full flower
  • decrease towards the end of summer as flowers drop.

The amount of hypericin varies with the type of St John’s wort. See the section on varieties below for more information on how to tell them apart. Hypericin levels increase during wet weather.

What does it look like?

From a distance an infestation appears:

  • yellow from November to January
  • dark green, brown and yellow from February to April
  • brownish-red in winter.

Leaves are:

  • paler green on the underside
  • opposite each other on the stem
  • spotted with oil glands – leaves can look like they have holes in them when held against a strong light.
  • without a stalk.

Flowers are:

  • bright yellow
  • about 20 mm in diameter
  • with five petals
  • with three bundles of long thread-like stamens growing from the centre
  • present from late October to January.

Fruit are:

  • a sticky, three-celled capsule
  • about 8 mm long
  • split open when ripening.

Seeds are:

  • in sticky seed capsules
  • small (0.5 – 1 mm)
  • cylindrical
  • light brown to black
  • with a pitted seed coat

Stems are:

Non-flowering stems:

  • grow from the crown
  • can form tangled thickets
  • are present in autumn and winter.

Flowering stems:

  • are upright and woody
  • sometimes have a reddish tinge
  • branch near the top
  • have two opposite ridges running the length of the stem
  • are produced in spring.

Roots are:

  • vertical – growing to about 1 m deep into the soil
  • horizontal – producing buds that form new growth above ground.

Varieties

There are two main strains of St John’s wort in NSW – broad-leaf and narrow-leaf strains. The strains have different toxicity levels at different times of the year. See the section on grazing timing below for more information on when to graze each variety.

Measure the leaves to tell them apart. Measure leaves at the 6th node (bump) on the flowering stem when the plant is growing well in spring. The narrow-leaf strain has leaves 7 – 9 mm wide. The broad-leaf strain has leaves 10 – 12 mm wide.

The narrow-leaf strain:

  • has more oil glands in the leaves
  • is late-flowering
  • is tall, growing to 90 cm
  • has thin stems
  • has small seed capsules.

The broad-leaf strain:

  • contains fewer oil glands in the leaves
  • is early-flowering
  • is short, growing to 60 cm
  • has thick stems
  • has large seed capsules.

Where is it found?

The heaviest NSW infestations are in the central and southern tablelands and slopes. The narrow-leaf strain is more widespread.

St John’s wort is native to Europe, Asia and North Africa. It was brought to Australia in 1875 as a garden plant. It is used in herbal medicine.

Distribution map

  • NSW (image)

What type of environment does it grow in?

St John’s wort grows in pastures, riparian areas, and bushland. It prefers:

  • rainfall over 600 mm per year
  • locations above 500 m altitude.
  • deep soils.

How does it spread?

By seed

The sticky seed capsules stick to animals. Seeds are also carried in the digestive tracts of animals. Wind spreads seed over short distances. Water, machinery, humans, livestock or feral animals spread seed over long distances.

By plant parts

Roots sucker and new plants grow from fragments. Cultivation can move root fragments.

More information

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Control

Long-term control of St John’s wort needs to consider that:

  • new seedlings appear from autumn to spring
  • seeds need mild temperatures, light and rainfall to develop
  • competition suppresses young seedlings
  • most new foliage grows in autumn and winter
  • foliage dies off in late spring
  • flowers develop in spring to autumn
  • new plants do not flower in the first year
  • seeds are released autumn to winter
  • a plant can produce up to 33 000 seeds per year
  • seeds can remain viable for 12 years.

Prevention

To reduce the risk of infestations developing:

  • learn to identify the weed and look for it in spring
  • minimise stock movements from infested to clean paddocks
  • quarantine livestock from a contaminated area for five weeks
  • clean vehicles that have passed through infested areas
  • buy certified seed
  • restrict feeding to flat, easy to monitor areas or paddocks with strong perennial pasture growth.
  • check feeding areas and control any St John’s wort plants (it’s best to also manually remove seed heads).
  • establish competitive perennial pastures along boundaries of infested paddocks – this acts as a buffer against further spread.

Pasture management

Healthy perennial pastures are the best long-term defence against St John’s wort. Good autumn and winter pasture cover can suppress new St John’s wort plants. To maintain healthy pasture cover:

  • grow combinations of winter and summer pastures
  • rest pastures between grazing periods
  • test soil to check fertility
  • control pests
  • use fertiliser if needed.

An agronomist can advise on a crop program to support St John’s wort control in arable areas. This can reduce the amount of St John’s wort seed in the soil before you sow a perennial pasture. A typical program might be to:

  • spray or plough in summer to reduce weed numbers
  • control weeds again in autumn before sowing a winter cereal or forage crop
  • repeat for a second year to decrease the number of St John’s wort seeds in the soil
  • sow a perennial pasture in the third autumn.

Sowing perennial pastures can help suppress St John’s wort even in less arable country. Use a direct drill/minimum tillage method to reduce soil disturbance. Control annual weeds over summer and again in autumn before sowing pasture. Allow the new pasture to set seed in the first year. Spot spray any new St John’s wort plants.

Grazing

Make sure there are shade trees in St John’s wort-infested paddocks for animals to shelter under. Grazing is usually the only practical way to control St John’s wort in steep areas.

Take care of animals when using grazing as a control strategy. Never graze when St John’s wort is flowering.

Sheep with superfine or fine wool are best suited for controlled grazing of St John’s wort. Superfine merino sheep are more than twice as tolerant to hypericin as medium wool merinos. Use adult merino wethers or dry, non-pregnant ewes with at least four months’ wool growth. Cattle, goats and other stock are less suitable.

Timing

Safe grazing periods are when the flowering stems are dead. The base of the plant will have soft, green shoots that are low in hypericin. Grazing hard in spring can delay flowering stem growth and extend the safe grazing period.

Broad-leaf St John’s wort has a longer grazing period. With sheep, graze:

  • broad-leaf from early May to mid-October
  • narrow-leaf from early July to mid-September.

In spring, move stock off St John’s wort pastures before flowering stems reach 5 – 10 cm.

Cattle can graze St John’s wort pastures about six weeks earlier than sheep. Cattle can also remain on St John’s wort infested pastures much longer than sheep in spring.

Change grazing periods based on the weather. Shorten during wet years as hypericin levels increase. Grazing can go longer when it’s dry.

Use short periods of intense grazing. Fence in heavy infestations of St John’s wort to encourage stock to intensively graze those areas.

Physical removal

Hand-weeding is not an effective way to control St John’s wort. The entire root system has to be removed to stop new plants from growing.

Cultivating tends to spread the weed unless all the roots are brought to the surface and dried out.

Fire

Burning can destroy seeds on the plant. The plant will regrow from the roots. Fire tends to cause more damage to pasture than to St John’s wort.

Biological control

Eleven biological control agents have been released in Australia. Six have established.

Chrysolina beetles

Chrysolina larvae and beetles feed on the leaves of St John’s wort. Larvae feed on winter growth. Adult beetles attack spring growth. Beetles can form dense infestations that remove all leaves on St John’s wort.

Chrysolina beetles are most effective when beetles and larvae feed in the same or consecutive years. They are only effective in unshaded situations as they mate only in sunlight.

Catch beetles in spring and move them to new infestations. Do not use herbicides when high numbers of Chrysolina beetles are present. Partially defoliated plants are unlikely to absorb enough herbicide to kill them.

Chrysolina hyperici and Chrysolina quadrigemina are black with bronze, dark-blue or purple reflections. They are oval shaped. C. quadrigemina is slightly larger (6.0 – 7.1 mm) than C. hyperici (5.3 – 6.1 mm). Some C. quadrigemina beetles are bluish.

Beetle (Agrilus hyperici)

Adult beetles are bronze coloured and 5 mm x 2 mm in size. They lay eggs in the crown of St John’s wort plants in summer. When they hatch, larvae bore into the roots and kill the plants. This beetle only lives in one or two isolated sites near Mudgee and Tuena.

Gall midge (Zeuxidiplosis giardi)

This small fly lays eggs in the terminal buds. When they hatch, larvae feed on the leaf buds and cause lumps (galls). Populations rarely get large enough to have an impact on St John’s wort infestations. The gall midge helps to control St John’s wort in shady country where other insects are not active.

Green aphid (Aphis chloris)

Green aphid attacks flowering stems of St John’s wort in summer. Populations rarely get large enough to have an impact on St John’s wort infestations.

St John’s wort stunt mite (Aculus hyperici)

The stunt mite affects the narrow-leaf form of St John’s wort. It is too small to see with the naked eye. The mites feed on the growing tips of plants. Damaged leaves often have yellow streaks or mottling. Rosettes and flowering stems are stunted. Mites can kill narrow-leaf St John’s wort over 2 – 3 years. All life stages are present throughout the year.

Chemical control

Only spray when St John’s wort is actively growing. Try to reduce damage to pastures through herbicide selection and timing. Two consecutive years of spraying is often required to kill plants. The deep, extensive root system can survive the first treatment, and the plant can regrow.

Spot-spraying

Spot-spray isolated infestations when St John’s wort is in flower (November to January). It’s too late once the flowers have turned brown. Cover all the foliage with herbicide.

Boom-spraying

Use boom-sprays between budding and full flowering (November to early January). If the existing pasture can be salvaged use selective herbicides. If the existing pasture cannot be salvaged, use glyphosate in November/December.

Weed wiper

Weed wipers can treat patches of St John’s wort. Graze useful plants below the wiper height before the start of St John’s wort flowering. Treat with the wiper at full flowering.

Herbicide options

WARNING – ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.

2,4-D LV ester 680g/L (Estercide® Xtra)
Rate: 3.3–4.7 L/ha
Comments: For use in grass pastures, before flowering, when the plants are less than 40 cm high.
Withholding period: 7 days
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Fluroxypyr 140 g/L + Aminopyralid 10 g/L (Hot Shot™ )
Rate: 700 mL in 100 L of water
Comments: Foliar application from flowering to early seed set
Withholding period: 7 days. See label for export restrictions.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Fluroxypyr 200 g/L (Starane™)
Rate: 500 mL in 100 L of water
Comments: Spring to mid summer application.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Fluroxypyr 200 g/L (Starane™)
Rate: 3.0 L/ha
Comments: Boom application. Observe withholding period.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Fluroxypyr 333 g/L (Starane™ Advanced)
Rate: 300 mL in 100 L of water
Comments: Foliar application from flowering to early seed set. Observe withholding period.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Glyphosate 360 g/L (Roundup®)
Rate: 3.0 L/ha
Comments: Apply November to May, flowering to post-flowering.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

Glyphosate 360 g/L with Metsulfuron-methyl 600 g/kg (Various products)
Rate: 200 mL glyphosate plus 10g metsulfuron-methyl in 100 L of water
Comments: Spray to wet, but not to cause run-off.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

Glyphosate 835 g/kg + Metsulfuron-methyl 10 g/kg (Trounce®)
Rate: 1 measured pack (173 g) in 100 L of water
Comments: Actively growing from spring to summer.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: B, Inhibitors of acetolactate synthase (ALS inhibitors) + M, Inhibitors of EPSP synthase
Resistance risk: High/Moderate

Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 500 mL in 100 L of water
Comments: Foliar application from late spring to early summer, during flowering to early seed set
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 2.0–4.0 L/ha
Comments: Boom spray
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Triclopyr 300 g/L + Picloram 100 g/L (Grazon® DS)
Rate: 500 mL in 100 L of water
Comments: Late spring to early summer, during flowering to early seed set.
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

Triclopyr 300 g/L + Picloram 100 g/L (Grazon® DS)
Rate: 500 mL per 10 L of water
Comments: Gas gun / Splatter gun application. Apply to actively growing bushes.
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
Central Tablelands Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land. The plant should not be bought, sold, grown, carried or released into the environment.
Protect grazing land that is free of St. John’s wort
North West
An exclusion zone is established for all lands in the region, except the core infestation area comprising the Gunnedah Shire council, Gwydir Shire council, Liverpool Plains Shire council and Tamworth Regional council
Regional Recommended Measure*
Whole of region: The plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: Land managers should mitigate the risk of new weeds being introduced to their land; land managers should mitigate spread from their land. Core infestation: Land managers reduce impacts from the plant on priority assets
Northern Tablelands Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land. The plant should not be bought, sold, grown, carried or released into the environment.
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfill the general biosecurity duty for this weed

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW DPI Biosecurity Helpline on 1800 680 244 or send an email to [email protected]

Reviewed 2018

  • Each plant can produce large quantities of seed, but output per plant is variable
  • The fruit is a sticky, 3-celled capsule (5 to 10 mm in length) containing many 1 mm long seeds
  • Seeds require light for germination and seedling growth is much slower than for most other grassland plants
  • This implies that germination and early growth are probably severely restricted or prevented under a strong pasture sward
  • Seeds can survive in the soil for 3 or more years
  • Stems usually die back in autumn, leaving prostrate leafy shoots that can form dense mats
  • In autumn or spring new crowns grow from lateral roots and eventually become separated from the parent plant. This can result in extensive population growth
  • Plants grow in a variety of dry, gravely or poor soils including wasteland, pasture, river beds and banks, roadsides, dunes, open scrub, open grassland, gravel pits, and railway ballast.

Origin

  • St John’s wort is native to Europe, western Asia, and North Africa and is now widely distributed through temperate areas, including parts of South America, India, Australia, and South Africa
  • Has been widely cultivated as a garden or medicinal plant, which might be part of the reason for its world-wide distribution
  • Considered a weed in much of its native range, particularly in Turkey, Italy, France, Hungary, and Sweden
  • First recorded in New Zealand in 1869 and is now found in many parts of North and South Islands in tussock grasslands, but also in pastures, riverbeds, waste places, on roadsides, and in many modified open communities.
  • Many other Hypericum species are found in New Zealand, including two native species and five introduced species that have been found growing outside their planted range
  • The two native species lack black glandular dots, and are low growing or mat forming plants.
  • The seeds have no special dispersal mechanism but may be spread by wind, water, animals, or by human activity, especially along roadways (e.g. vehicles, metal dumps etc.)

Benefits

  • In Europe St John’s wort has long been used for a variety of purposes, from treating burns and skin disorders through to depression. It has been used as an ingredient for distilling vodka, and as a source of red, yellow, purple and orange dyes
  • In folklore St John’s wort was thought to possess magical properties, and was used as a charm against storms, thunder, evil spirits, and witches. It was claimed to bring good luck if sprigs of the plant were hung about the house or carried as a charm and, if you slept with them under the pillow, you would dream of a future lover
  • In herbal medicine St John’s wort is commonly recommended as an anti-depressant but health authorities say that it can interfere with other medications and should be used with caution.

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