St. John's Wort

Description

St. John's Wort belongs to the Clusiaceae family and can grow up to one metre tall. It has numerous bright yellow flowers, 2 cm in diameter occuring in flat-topped clusters. The flowers have 5 separate petals that are 2 times as long as the septal. The leaves are opposite, oval-shaped, with prominent veins, 1-3 cm. long and covered with transparent dots. The stems are erect, 2-sided, rust coloured, and have numerous branches (Ministry of Agriculture, Lands, and Fisheries, 2002). This plant is native to Europe but arrived in North America in the late 1700s and become an established weed in BC in the 1940s (White et al 1993).

Type

Perennial forb

Habitat & Impacts

St. John's Wort invades grazed and disturbed lands along roadsides and grows in low to mid-elevations in coastal, grassland, and open forested regions. It can displace native plant species and reduce livestock and wildlife forage. (Ministry of Agriculture, Lands, and Fisheries, 2002). The plant contains a phototoxin which can cause skin irritation to livestock with light coloured skin when exposed to sunlight. It is generally not palatable to cattle (Majak et al 2008) St- John's Wort is also known to be a skin irritant for humans.

Method of Spread

St. John's Wort reproduces by seed and vegetatively from the roots. The rhizome root system spreads laterally and is capable of forming new buds that separate from the parent. Each plant produces approximately 15,000- 30,000 seeds. The seeds have a gelatinous coat that allows long-distance dispersal and can remain viable in the soil for 6-10 years. (Ministry of Agriculture, Lands, and Fisheries, 2002).

Location

St. John's Wort is not well established in the Cariboo Chilcotin Coast Region. Most infestations have been located in the Bella Coola area and Tweedsmuir Park; however, a few sites have been located in the Quesnel area.

Mechanical

Can be managed by tillage in agricultural fields.

Chemical

Combinations of 2,4-D and picloram, or 2,4-D, and glyphosate have been successful in managing this weed in the US (Ministry of Agriculture, Food and Fisheries, 2002).

Biological

Several biocontrol agents are available for St. John's Wort including Agrilus hyperici (root feeding beetle), Aphis chloris (sap sucking aphid), Aplocera plagiata (foliar feeding moth), Chrysolina hyperici (foliar feeding beetle), Chrysolina quadrigemina (foliar feeding beetle), Chrysolina varians (foliar feeding beetle). Chrysolina hyperici and Chrysolina quadrigemina have been successful in the Kootenay region of BC but none of these agents have been tested in the CCCIPC region (Ministry of Forests and Range, 2007).

CCCIPC Priority & Treatment Strategy

Priority4 (Biological Control)

Local Level

Chemical control and tillage for agricultural sites.

Landscape Level

Biological control for larger infestations.