Kalm’s St. John’s-Wort is a sun-loving, low, mounded shrub endemic to the Great Lakes region. In the wild, it is typically found growing in rocky or sandy soils near ponds and interdunal swales. It prefers moist growing conditions, and with excellent drainage it can tolerate average garden situations. It is a handsome, low-growing shrub with bluish-green foliage in summer and bright yellow, 1-1½” five-petaled flowers from July to August. These flowers do not produce nectar and only attract various small bees which collect their pollen. They are long-blooming and add a cheerful pop of color to rock gardens, shrub borders and around the edges of ponds. They are moderately salt tolerant and a suitable choice for planting near driveways and sidewalks.
*This is not the species renowned for its medicinal properties which is the non-native, invasive Hypericum perforatum.
Sources:
Native Trees, Shrubs, & Vines by William Cullina
Manual of Woody Landscape Plants by Michael A. Dirr
Midwestern Native Shrubs and Trees by Charlotte Adelman & Bernard L. Schwartz
Missouri Botanical Garden
Lady Bird Johnson Wildflower Center
Illinois Wildflowers
ODNR
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Hypericum kalmianum (Kalm's St. Johns-Wort) - QT
Kalm's St. Johns-Wort
Plant Care & Installation Quick-Guide
Proper acclimation and installation are key to your plant's success. Please cross-reference these tips with your plant's specific ID tags:
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Pre-Planting: Store plants in a light-appropriate area on soil or grass (avoid hot concrete or asphalt) and water daily until the soil is saturated and the pot feels heavy. If temperatures drop below 30°F, move pots to a garage or cover them to prevent root freeze.
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Installation: Dig a hole matching the depth of the pot, remove the fabric container, and ensure the plant’s crown or root flare is level with the ground. Fill gaps with soil, water heavily, and apply 2 inches of mulch—keeping it clear of the stem.
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Ongoing Care: Check moisture daily by feeling 1–2 inches into the soil; water deeply at the base if the soil feels dry or warm. Newly installed plants require frequent watering (up to 3–4 times weekly in heat) until fully established, which can take a few months for perennials and up to two years for trees.