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Plant Profile: Common St. John’s Wort (Hypericum perforatum)

Also called goatweed or Klamath weed this herbaceous perennial native to Europe, western Asian and North Africa  where it occur in a wide variety of habitats including pastures, meadows, rangelands, woodlands, open forests, natural clearing,  moist ravines, abandoned fields, roadsides,  and ditches.  It belongs to the Hypericaceae plant family that includes no other well known genera.  The root system consists of one or many aerial crowns attached to a system of vertical and lateral roots.  The vertical roots reach a depth of  two to five feet white the lateral roots are 1.2″ to 3″ deep and produce new crowns. Plants generally grow one to three feet tall but can reach five feet, and have one to many erect often reddish stems that are woody at the base, branched in the upper half ,and have pale green to yellow-green  oblong or linear round tipped leaves.  The leaves  are  attached directly to the stem and have  scattered translucent dots created by the presence of  glands.  The  flowers  are 3/4 inch across and appear in terminal compound cymes of 25-100 all summer.  They  have five yellow petals with black dots on the edges and give way to round seed pods that have a pointed tip. Common St. John’s wort has been grown since ancient times as a medicinal herb but causes many health problem  including allergic reactions and interference with prescribed medications. It also causes problem for livestock and is considered an invasive weed in many places.  The genus name, Hypericum, is from the Greek word hypereikon and derived from hyper, meaning above, plus eikon meaning picture.  The plant was believed to keep evil spirits away and the flowers of some species were placed above pictures, windows or doorways for this purpose at the ancient summer solstice festival which later became the feast of St. John, June 24.  The specific epithet, perforatum, is the Latin word meaning having or appearing to have small holes and refers to the holes that the Devil pierced in the leaves with a needle in revenge for people using the flowers to repel evil spirits.  The holes are actually translucent glands.

Type: Herbaceous perennial

Bloom: Terminal clusters of 25-100 yellow 3/4″  flowers all summer

Size: 1-5′ H x 3/4-2′

Light: Full sun to partial shade

Soil: Average, moist, well-drained, acid; prefer snady or gravely soils.

Hardiness: Zones 5-9

Care: Restrict growth to prevent unwanted spreading

Pests and Diseases: None of significance

Propagation: Seed, cuttings, division

Companion Plants: Other medicinal herbs in an herb garden or other plants associated with the Jesus and Mary  in a Marian garden

Photo Credit Wikimedia Commons