Common Name: St. John's wort
Type: Deciduous shrub
Family: Hypericaceae
Zone: 5 to 8
Height: 0.50 to 1.00 feet
Spread: 1.00 to 2.00 feet
Bloom Time: July to August
Bloom Description: Yellow
Sun: Full sun to part shade
Water: Medium
Maintenance: Low
Suggested Use: Naturalize
Flower: Showy
Leaf: Colorful
Tolerate: Drought, Erosion
Culture
Easily grown in average, medium, well-drained soil in full sun to part shade. Tolerates wide range of soils. Thrives on sandy soils in full sun. Less floriferous in part shade. Evergreen in warm winter climates. Usually dies to the ground or suffers some tip dieback in cold winter climates, but blooms on new growth and comes back nicely each spring. In areas where it does not die in winter, shear or mow plants in late winter or early spring every 2-3 years to renew and induce new growth. Spreads rapidly by underground stems and can spread aggressively in ideal growing conditions. Plant 18" apart for use as a ground cover.
Noteworthy Characteristics
Hypericum calycinum is a stoloniferous subshrub or shrublet, typically growing 12" (less frequently to 18") high and 24" wide, which is frequently planted as a ground cover. Features large, rose-like, 5-petaled, yellow flowers (2-3" diameter) having numerous, bushy stamens with reddish anthers. Flowers appear singly or in groups of 2-3 and cover the plant in summer. Oval to oblong, distinctively net-veined (from beneath) leaves (to 4" long) are rich green in sun but are a lighter, yellowish green in shade. Four-angled stems are both procumbent and ascending. Sometimes commonly called Aaron's beard or creeping St. John's wort.
Genus name comes from the Greek words hyper meaning "above" and eikon meaning "picture" in reference to the practice of hanging flowers from this genus above images, pictures or windows.
Specific epithet means calyx-like.
Plants of the genus Hypericum (some species have been used since ancient times in the treatment of wounds) 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.
'Briggadoon' is a golden-leaved form of the species. It features large, rose-like, five-petaled, yellow flowers (2-3" diameter) having numerous bushy center stamens with reddish anthers.
Problems
No serious insect or disease problems of a frequently occurring nature. Wilt and root rot can be significant problems, particularly in hot and humid climates of the South.
Uses
Mass as a ground cover. Rock gardens, border fronts, naturalized plantings. Edger for open woodland gardens. Also effective massed on slopes, hillsides or embankments for stabilizing soils. Plant under trees where it competes well with shallow tree roots. Allan Armitage calls the species "one of the finest ground covers available".