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St Johns Wort

St J wort plant

St J wort flowers

St J wort flower

St J wort rosette

St J wort old seed heads

St J wort infestation

Hypericum gram1

Hypericum gram2

Tutsan1

Tutsan2

   


BOTANICAL NAME:

Hypericum perforatum


Family:

Clusiaceae

Status:

St John's wort is declared noxious in class 3 in Bega Valley, Eurobodalla, Goulburn-Mulwaree, Illawarra, Palerang, Queanbeyan and Shoalhaven LCAs and in class 4 in Bombala, Cooma-Monaro, Snowy River, Southern Slopes, Upper Lachlan and Wingecarribee LCAs, reflecting the fact that it is less well-established on the coast than on the tablelands and slopes.

Description

St John's wort is a perennial herb with small pale green leaves arranged in opposite pairs. If the leaves are held up to the light, tiny clear oil dots can be seen. Five-petalled yellow flowers are about 20 mm diameter. Flowering is in summer. Seed is tiny and contained in small brown papery capsules. The plant dies back to the rootstock over winter and does not begin growing again until early summer.

Preferred habitat and impacts


Grows in pasture where it reduces carrying capacity, and on road verges and other waste ground, and is very invasive in grassy woodlands. The plant is poisonous to stock causing photo-sensitisation, particularly in white-faced animals. Those with darker pigmentation are less affected. The faces and mouths become itchy and raw, preventing feeding.  Reaction to the plant increases with exposure. Contact with the plant has also been associated with mild poisoning in people. Symptoms include dizziness, loss of appetite, lethargy and diarrhoea.

Dispersal

Seed sticks to animals or vehicles, is spread in contaminated soil, or in hay or chaff. Each plant also produces underground runners which can be spread by cultivation.

Look-alikes

The native Hypericum gramineum is very much smaller with flowers only 5-10mm diameter. It is a common herb in grassy woodlands and is not a problem for livestock. Several larger Hypericum species are used as garden plants. Tutsan (H. androsaemum) is an occasional garden escape in the region. It has similar but much larger leaves and flowers and black berries. It prefers moist shady sites.

Control

Very small infestations can be hand dug taking care to remove all of the underground stems and dispose of them carefully, although this is seldom practical. If handling this plant, wear gloves. Spot spraying is more effective, preferably with a selective herbicide to avoid killing grass and creating bare ground. Boom spray or cultivate for large infestations. Use tined implements to avoid spreading root fragments. St John’s wort does not tolerate strong competition from healthy pasture so avoid over-grazing and ensure rabbits are controlled. Well timed grazing by goats or sheep can assist with control.