St. Johnswort, Hypericum, is evergreen, semi-evergreen, and sometimes deciduous groundcover or small shrub is grown for its bright yellow flowers that bloom throughout the summer over blue-green leaves. The flowers have prominent, showy yellow stamens.
Hypericum is a genus composed of a large number of perennials and shrubs, most are decorative having bright yellow flowers with profuse stamens and often evergreen foliage.
Hypericum is grown in the rock garden, in borders, and the species which sucker readily are used for ground-cover landscape work. They grow easily in loamy or sandy soil and their blooming period is prolonged if they are given a semi-shaded position.
St. Johnswort grows readily from seed though the creeping species are also increased by suckers and division.
Get to Know St. Johnswort
- Plant type: Deciduous or evergreen shrub used as a groundcover
- Growing Zones and range: 5-9
- Hardiness: Blue-green leaves of varied size and shape are opposite
- Height and width: 12 to 18 inches (30-45cm)tall and wide
- Foliage: Shiny 4-inch (10cm), blue-green leaves are evergreen in warm climates
- Flowers: Bright yellow 2-3 inch (5-7.6cm) wide flower with showy stamens
- Bloom time: Summer
- Uses: Plants spread quickly via stolons; fill in dry spaces, shady areas, beneath trees
- Common name: Aaron’s Beard, St. Johnswort
- Botanical name: Hypericum calycinum
- Family: Hypericaceae
Where to Plant St. Johnswort
- Plant St. Johnswort in partial to dense shade.
- Grow St. Johnswort in moist, humus-rich, well-drained soil. Established St. Johnswort tolerates dry conditions.
When to Plant St. Johnswort
- Set St. Johnswort in the garden in spring.
- Start seed indoors in late winter for transplanting to the garden in spring after the last frost.
Planting and Spacing St. Johnswort
- Space St. Johnswort 12 to 18 inches apart.
- Sow seed 1/8 inch deep in six-packs or flats filled with light potting mix or sow outdoors in evenly prepared soil.
How to Water and Feed St. Johnswort
- St. Johnswort wants moderate to abundant water; keep the soil evenly moist. Established plants are drought tolerant.
St. Johnswort Care
- Mulch around St. Johnswort to conserve moisture.
- Divide plants every two to three years to keep St. Johnswort from becoming invasive.
- Each spring, cut back St. Johnswort to the ground to encourage good flowering.
St. Johnswort Propagation
- Stems root as they rest on the soil.
- Root softwood cutting in spring.
St. Johnswort Varieties to Grow
- Hypericum androsaemum: Semi-evergreen shrub grows to 3 feet tall with arching stems; clusters of golden yellow flowers; good groundcover.
- H. beanii (H. patulum henryi): Evergreen shrubs grows to 4 feet tall; willowy branches; golden-yellow flowers 2 inches across from midsummer to fall.
- H. calycinum, Aaron’s beard, creeping St, Johnswort: Semi-evergreen shrublet grows to 1 foot tall; spreads by underground stems; bright yellow 3-inch flowers; tough groundcover.
- H. frondosum: Deciduous shrub can grow to 3 feet tall; blue-green leaves; clusters of bright yellow flowers in midsummer.
- H. ‘Hidcote’: Semi-evergreen perennial has large golden flowers in summer; it grows 3-4 feet tall and 4-5 feet wide.
- H. kalmianum, Kalm’s St. Johnswort: Dense evergreen grows to 3 feet tall; blue-green leaves with clusters of 1-inch flowers in summer.
- H. moseranum, gold flower: Evergreen shrub grows to 3 feet tall; moundldike habit with arching reddish stems; golden yellow flowers in clusters of up to 5.
- H. patulum henryi. See H. beanii.
- H. reptans: Evergreeen shrublet is flat growing with 1-inch flowers in summer.