There are a great number of St. Johnsworts in the genus Hypericum. The flowers are generally yellow and in terminal clusters. The Common St. Johnswort, is an introduced plant from Europe that is an erect perennial, growing to 3 feet high on a branching hairless stem. The larger stems have a pair of ridges formed on opposite sides of a swelling at the base of the leaves. Branching is vigorous in the inflorescence.
Leaves are very narrow, oblong, stalkless, that have numerous translucent dots, which are the oil producing cells. These dots which look like "perforations" are what caused Linnaeus to name the plant H. perforatum.
The inflorescence is a loose cluster of several flowers at the top of the stems. There is much branching in the inflorescence and thus many small clusters. Each flower is stalked.
Flowers: The five golden yellow flower petals have margins spotted with small black dots. The petals have a ragged edge and spread out like a flat plate when fully open. Their shape is elliptical - widest in the middle. Flowers are about one inch wide, with 3 styles, numerous stamens that are united at their bases into 3 sets; filaments and anthers are yellow. The calyx has 5 green sepals which are long and narrow and shorter than the petals.
Seeds: The flower petals turn brown and remain in a shrunken twisted shape on the developing seed pod which is a 3-celled capsule containing numerous brownish-black seeds.
Varieties: There are four varieties found world-wide, but only one in North America - var. perforatum.
Habitat: The plant has a taproot and a rhizomatous root system from which multiple stems can arise. It prefers full sun and adapts to dry conditions. It can spread rapidly and can be noxious in pasture areas and thus it is listed as a noxious weed by a number of states that have large grazing lands such as Colorado, Nevada, Wyoming and Montana among others. The alternate common name of 'Kalmath Weed' is in recognition of that in the western grazelands of the U.S. Nevertheless, it is an attractant to pollinators and very useful in restoring pollinator habitat.
Names: Some references will assign this plant to the family Clusiaceae. That is not accepted by most authorities including the U of M Herbarium on their Checklist of the Vascular Flora of Minnesota. The genus Hypericum is from the Greek hyperikon, meaning 'above picture' or 'above an apparition' and refers to the old practice of placing a sprig of a Hypericum above images or in the house to ward off evil at such times as the during the old festival of Walpurgisnacht and especially on midsummer eve, the night before St. John's Day. (see next paragraph) The species perforatum means having or having the appearance of small holes - as in the translucent dots on the leaves of this species. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
The common name of 'St. Johnswort' is a European reference to St. John's Day, a church feast date on June 24th when the plant would usually be in flower; the 'wort' portion referring to the plants healing properties. The eve of St. John's Day (San Giovanni in Italy), midsummer eve, June 23rd, is considered a night for spirits and witches. It is several days after the actual Summer solstice date but is a remnant of the old Julian calendar.
Comparisons: Great St. Johnswort, Hypericum pyramidatum, is native and also grows in the Garden. The leaves are different as is the flower structure.
Common St. Johnswort: Blooms begin in late June with much branching in the inflorescence. 2nd photo - one of the last blooms of late August, but depending on the year, it may bloom even later. Near it are numerous developing seed capsules and note the brown twisted remains of the petals.
Below: 1st photo - Petals have a ragged edge. In the center the flower has 3 styles from the pistil, surrounded by 3 sets of numerous yellow stamens. 2nd photo - The green sepals of the calyx are very narrow and much shorter than the petals.
Below: The small opposite leaves. Note the light colored translucent dots on upper surface (1st photo). These appear darker on the underside (2nd photo).
Below: 1st photo - At the base of the larger leaves there is a swelling that forms a pair of ridges on opposite sides of the stem. 2nd photo - The developing seed capsules are 3-chambered and have the the remains of the 3 styles at the top and the brown petals at the base.
Below: A pair of flowers of Common St. Johnswort. Note the 3 long styles spreading outward from the pistil of the ovary and the numerous black dots on the margins of the petals. The numerous stamens are united at their bases into 3 sets.
Below: A grouping of plants in the Upland Garden in July.
Notes: Common St. Johnswort - Eloise Butler's records show that she obtained plants of this species on April 4, 1912, on April 4, 1913, on April 28, 1916 and on April 2, 1925, all from Malden, Massachusetts. This was where Eloise's sister, Cora Butler Pease, lived and to where, after 1911, Eloise would return in the late Fall to spend the winter. She either collected these herself, or Cora did, and then had them shipped to her in Minneapolis. Martha Crone planted it in 1946. There are seven known species of St. Johnswort in Minnesota, the "Common" is not native, but introduced into the United States and to Minnesota, and is found most often in scattered counties in the eastern section of the state. There are very few states or lower Canadian Provinces where it is not found.
Problems: In our western states, beginning from the rangeland of northern California near the Klamath River, the plant spread widely over the rangelands of the western states, taking over from beneficial rangeland plants. This is how the alternative common name of Klamath Weed became applied. The edible parts of the plant are toxic to cattle as cattle react to the chemical "hypericin" contained in the plant. In the mid 20th century, first in Canada, then in the west, beetle control was introduced from Europe in the form of three species of the Chrysolina beetle, which feeds only on the leaves of Common St. Johnswort. The most commonly used species is C. quadrigemina. These beetles greatly reduced the abundance and spread of the plant.
In humans the ‘hypericin’ in the flowers and leaves, is a photo sensitizing agent that reacts with light to cause skin burns on light-skinned people. Some have made tea from the flowers but good advice is to not drink it due to the hypericin.
The seven species of Hypericum found in Minnesota are: H. boreale, Northern St. John's-wort; H. ellipticum, Pale St. Johnswort; H. kalmianum, Kalm's St. Johnswort (undetermined if native); H. majus, Large St. Johnswort; H. perforatum; H. punctatum, Spotted St. Johnswort; and H. pyramidatum, Great St. Johnswort.
Lore: H. perforatum has a long history as a medicinal ingredient and is available as an over-the-counter herbal supplement today to help with numerous maladies. The medicinal parts are the plant tops and flowers. Edwin Way Teale (A Walk Through the Year) reported that "During medieval times it was gathered and hung in doors and windows to ward off evil spirits. Its name comes from an old belief in England that it begins to bloom on June 24, the day of St. John the Divine." Less well known is that a small quantity added to bread flour is said to improve the quality of bread.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"