Culture
Easily grown in average, medium moisture, well-drained soils in full sun to part shade. Prefers moist, rich, sandy loams. Tolerates poor soils. Established plants tolerate some drought. Prune if needed after bloom in late summer.
Noteworthy Characteristics
Hypericum kalmianum, commonly called Kalm St. Johns wort, is a small, dense, evergreen shrub or subshrub with upright branching that typically grows in a dense mound to 2-3’ tall. It is native to the Great Lakes region of the U.S. where 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 (to 2” long) in pairs on distinctive 4-angled stems are evergreen but some may drop in winter. Five-petaled, golden yellow flowers (1.5-inch diameter) in 3- to 7-flowered cymes bloom in mid to late summer (July-August). Each flower has five styles and a distinctive center boss of yellow stamens. Flowers give way to beaked, oval, brown seed capsules that mature in fall and often persist on the shrub until spring. Leaves are dotted with tiny glands.
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 honors Peter Kalm, a student of Linnaeus, who reportedly discovered this plant in the wild in North America in the mid-1700s.
'Deppe' is commonly sold in commerce under the trade name of SUNNY BOULEVARD. It is the product of an open pollination of H. kalmianum 'Gemo' (seed parent) and an unknown selection of H. kalmianum (pollen parent) that occurred in a controlled breeding program in Grand Haven, Michigan in 2002. It is distinguished by its compact-mounding form, dark green leaves, bright yellow flowers and free-flowering habit. SUNNY BOULEVARD typically grows to 2-3' tall. U.S. Plant Patent PP20,045 was issued on June 2, 2009.
Problems
No serious insect or disease problems.
Uses
Low hedge, border or rock garden. Wood margins, rocky slopes, wild gardens, naturalized areas or pond peripheries.