St. John’s wort

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St. John’s Wort control

Access all the information needed for control of this noxious weed, including weed identification, herbicide application and spray timings.

St. John's Wort Description

St John's Wort Identification

St. John’s wort is a perennial herb that can grow up to 1 m tall. It has stemless small leaves dotted with clear oil glands that have a perforated appearance when held to light. Stems are reddish in colour.

Flowers have five yellow petals, three bunches of many stamens. St. John’s wort is widespread in pastures, water catchment reserves, forests and national parks and can cause photosensitisation in livestock.

It infests large areas of New South Wales, Victoria and South Australia and is a serious weed on tablelands and slopes areas as it is most suited to areas receiving more than 600 mm annual rainfall at altitudes of 600 m to 1500 m.

St. John's Wort Control

Controlling St. John’s wort

For control of St John's Wort, apply high-volume hand spraying of Grazon Extra at a rate of 500 mL/100 L of water applying 3000 L/ha to thoroughly wet the foliage of a dense infestation; lower spray volumes (2000 L/ha) will be effective on moderate to sparse infestations. Boom spraying with Starane Advanced at 1.8 L/ha and 200–250 L of water/ha is also effective and aerial application via helicopter using Grazon Extra at 4 L/ha is effective for hillside spraying.

Ensure the plant is actively growing (15–50 cm tall), and both the upper-flower canopy and sub-canopy lying prostrate are wet. Focus on spraying open areas where pasture productivity can be improved by the removal of St. John’s wort without damaging remnant vegetation.

Herbicides for Control of St. John’s wort

Method of application Rate* State
Grazon™ Extra Herbicide Foliar spray 500 mL/100 L of water
Hotshot™ Herbicide Foliar spray 700 mL/100 L of water All
Starane™Advanced Herbicide
Foliar spray 300 mL/100 L of water All
Stinger™ Herbicide + Glyphosate 450 Foliar spray 20 g + 160 mL/100 L of water + Pulse™ WA, NSW, SA, Vic
Tordon™ 75-D Herbicide Foliar spray 500 mL/100 L of water Qld, ACT, NSW, SA, Vic, WA
Grazon Extra
Boom application 2 to 4 L/ha ACT, NSW
Starane Advanced Boom application 1.8 L/ha (200 L water/ha) All
Esteron™ LV Herbicide
Boom application 3.26 to 4.68 L/ha NSW, Qld, ACT, WA, Vic
Grazon Extra
Controlled droplet application apply undiluted
Grazon Extra Gas gun application 500 mL/10 L of water ACT, NSW, Tas, Vic
Grazon Extra
Aerial (helicopter only) 4 L/ha ACT, NSW

#Note: Preferred product option in bold. *Consult label for details of growth stage and use, especially where range of rates is given.

Treatment Timing

Timing for St. John's Wort Control

Spot spraying is best carried out when St. John’s wort is in flower (Nov–Jan) because it can be easily seen then and is at its most sensitive period to herbicides. Spraying should begin six to eight weeks after substantial rain and when St. John’s wort reaches the 50% yellow bud – 50% open flower stage.

PRODUCT Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Grazon Extra
Best time to spray/treat
Can spray/treat
if conditions are suitable
Do not spray/treat