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Species Spotlight: Shrubby St. John's Wort (Hypericum prolificum)

Updated: Dec 11, 2022

St John's Wort flower

Interesting Facts:

  • Genus name comes from the Greek words "hyper" meaning above and "eikon" meaning picture, a reference to the practice of hanging flowers from this genus above images, pictures or windows.

  • Hypericum (some species have been used since ancient times in the treatment of wounds and inflammations) were apparently gathered and burned to ward off evil spirits on the eve of St. John's Day, thus giving rise to the genus common name of St. John's Wort.

  • Ingesting St John's Wort can reduce the effectiveness of prescription medicines.<2>

  • Poison Severity: Medium; Poison Symptoms: Skin contact with the sap, or ingestion of the plant, can cause photosensitivity in some people. Common side-effects are gastointestinal disturbances, allergic reactions and fatigue. <2>

Native Environment/Plant Information:

Shrubby St John’s Wort is a compact, deciduous, rounded shrub with an erect habit. Shrubby St John’s Wort typically grows 1-4' (less frequently to 5') tall and has rhizomatous roots. Stems of young stems are green and slightly winged but eventually become woody with a rough grey-brown texture. Bark of older stems exfoliates to reveal attractive, pale orange inner bark. Leaves are medium green, narrow and hairless and often measure 1-3" long and ¼-½" wide.Upper stems terminate in small clusters of 3-7 flowers in June and July around here. The bright yellow flowers are about 1” in diameter and each have five petals and numerous yellow stamens. The flowers only offer pollen to pollinators. The flowers have so many stamens they often obscure the petals, hence the scientific species name “prolificum”. Fertilized flowers are replaced with ¼-½” cone-shaped seed capsules that split in august to release their black seeds

Shrubby St John’s Wort is most commonly found in dry, sunny locations. Shrubby St John’s Wort is most commonly found on rocky ground, open woods, dry wooded slopes, uncultivated fields. It is most commonly found at locations underlain with limestone.

Shrubby St John’s Wort is similar to Golden St John’s Wort (Hypericum frondosum). Golden St. John' Wort, has larger flowers (greater than 1" across) and wider leaves (greater than ¾" across) than Shrubby St. John's Wort. Golden St. John's Wort is native to the southeastern states.

Cultural Information:

Shrubby St John’s Wort is easiest to grow in sunny locations. It is adaptable to shadier conditions but prefers at least 6 hours of sun. It is adaptable to both moist and moderately dry ground and tolerates a wide range of soils, including dry rocky or sandy soils. It is readily cultivated in gardens and tolerates some drought.

Shrubby St John’s Wort blooms on the current seasons growth, meaning it can be pruned anytime between the period after flowering has finished and before growth starts in the spring. The best time to prune is late winter before growth starts. Shurbby St John’s Wort is low maintenance, and tolerates drought, sandy or clay soils, black walnut, and deer/rabbits. Its rhizomatous roots do send shoots along their length, but the plant can be be kept under control with spring pruning. This is also part of why Shrubby St John’s wort works well for erosion control.

Shrubby St John’s Wort works well planted in mass or grouped in a shrub border or native plant garden. It can also be grown as a hedge and is useful for stabilizing embankments.

St John's Wort

Wildlife uses:

Shrubby St John’s Wort’s bright yellow flowers are loved by bees, which collect pollen for their larvae. Other insect visitors using the pollen include Syrphid flies and Halictid bees, but these pollinators are less effective at cross-pollination. The flowers only offer pollen. Shrubby St John’s Wort is a host plant for the aphid Aphis hyperici and other aphids, the leafhoppers Erasmoneura margaritae and Erasmoneura rubricata, Paria sellata and other leaf beetles, caterpillars of the butterfly Gray Hairstreak (Strymon melinus), Gray Half-spot (Nedra ramosula) and other moths, and Clastoptera hyperici (St. John's Wort Spittlebug).

Birds are attracted to the fruits and small seeds.

Most mammalian herbivores avoid consumption of Hypericum species because their foliage contains varying amounts of the phototoxic chemical, hypericin. In the presence of light, this chemical can cause rashes to develop on light-skinned animals, and it can irritate the gastrointestinal tract.

Honey bee on St John's Wort flower

Useful Links and References:

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