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St. John's wort

(Hypericum perforatum)

St. John's wort (Hypericum perforatum) has increased in recent years.  With several large infestations in the Boundary.  There was a large infestation in the path of the 2015 fire in the Rock Creek-Westbridge area.  


St. John's wort is a perennial that grows from underground runners.  It grows from 0.3 to 1 m in height.  Transparent dots are visible over the surface of the oblong leaves when held to the light.  It has bright yellow flowers with 5 petals.  Plants turn a rusty red colour at maturity.


St. John's wort is controlled by bio-agents.  Mainly Chrysolina species beetles.  There was a crash in insect populations but the past few years have shown a rise in populations.  Selective herbicides are effective.


St. John's wort contains a toxin that causes grazing animals to become sensitive to sunlight resulting in intense skin irritation.  St. John's wort is also used medicinally for depression but you should speak to a health care professional before taking it as it can cause photo sensitivity and can cause liver failure if you take too much.


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