Kalm St. Johns Wort, Hypericum kalmianum

Kalm St. Johns Wort

Hypericum kalmianum

Benefits: Pollinator Benefit Graphic
Sun Shade: Plant Light Requirements Graphic
Bloom Time: Late Summer/Early Fall
Hardiness Zones: 4, 5, 6, 7
Soil Conditions: Loam, Sand
Soil Moisture: Medium, Moist
Color: Yellow
Fragrance: No
Height: 2-3 feet
Spacing: 2-3 feet

Kalm St. Johns Wort, Hypericum kalmianum, is a small, dense, evergreen shrub or subshrub with upright branching that typically grows in a dense mound to 2-3 feet tall. It typically occurs in rocky to sandy soils, ranging from relatively dry open woods to moist lakeshore areas. Narrow, linear-oblong, stalkless, bluish-green leaves in pairs on distinctive 4-angled stems are evergreen but some may drop in winter. Five-petaled, golden yellow flowers in 3- to 7-flowered cymes bloom in mid to late summer. Each flower has five styles and a distinctive center boss of yellow stamens. The blooming period occurs from mid-summer to late summer, lasting about 1 month. Afterwards, the flowers are replaced by seed capsules about 8 mm. long that are lanceoloid in shape and 5-lobed. The interior of each seed capsule has 5 completely separated cells. There are numerous seeds in each cell. These seeds are dark-colored, narrowly oblongoid, and somewhat flattened. The woody root system is shallow and spreading.

Habitats include inter-dunal swales, borders of small sandy ponds, moist to wet sandy meadows, and moist sand flats. This shrub is found in high quality natural areas.

Easily grown in average, medium moisture, well-drained soils in full sun to part shade. Prefers moist, rich, sandy loams. Established plants tolerate some drought.

 Plant Notes and Herbal Uses
  Prune if needed after bloom in late summer.
  Cultivated in gardens because of its showy flowers.
  Tolerates poor soils.
 Further Information

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