Kalm's St. John's Wort (Hypericum kalmianum)
hy-PARE-ih-kum kal-mee-AY-num

Deciduous Perennial Shrub, Mounded in the Hypericaceae Family
A hardy native shrub with cheerful yellow summer flowers and easy wet-or-dry adaptability.

Hypericum kalmianum, commonly called Kalm's St. John's Wort, is a native North American shrub hardy in USDA Zones 4a-7b. It grows naturally in moist, open areas and along woodland edges throughout the northeastern and north-central United States and eastern Canada, including the shorelines of the Great Lakes.

This compact, deciduous shrub typically reaches 2-4 feet tall and 2-3 feet wide, with a rounded, mounding growth habit. Its narrow, blue-green leaves have a slightly glaucous cast and turn a coppery bronze in fall. From midsummer into early fall, the shrub produces an abundance of bright golden-yellow, five-petaled flowers about 1 to 1.5 inches across, each with a prominent cluster of stamens.

Kalm's St. John's Wort prefers full sun to partial shade and moist, well-drained soil, tolerating a wide range of pH from acidic to alkaline. It is drought-tolerant once established and also tolerates brief periods of standing water, making it a versatile choice for rain gardens and pond edges as well as drier sites. Its nectar-rich flowers are a valuable food source for bees and butterflies, and its persistent, chocolate-brown seed capsules add winter interest.

Pros

  • Long season of cheerful, bright yellow flowers from midsummer into fall
  • Genuinely adaptable to both wet and dry sites once established
  • Low-maintenance, pest- and disease-free, and deer/rabbit resistant
  • Great Lakes native that supports bees and butterflies

Cons

  • Foliage and seed capsules are toxic to pets and livestock if ingested
  • Can spread slowly by suckers over time
  • Fall color is subtle (coppery bronze), not a standout autumn feature
Why Like A true Midwest and Great Lakes native, Kalm's St. John's Wort fills an important niche along lakeshores and wetland margins, where its nectar-rich flowers support bees and butterflies through the heart of summer. Its tolerance for both occasional flooding and drought reflects its adaptation to fluctuating shoreline water levels in the wild.
Highlights A tough, adaptable native shrub with months of cheerful yellow blooms, standout winter seed heads, and genuine wet-or-dry-site versatility.
 

Plant Data

Mature Size 24 - 48 inches tall. 24 - 36 inches wide.
Growth Rate Moderate
Sun Exposure Partial Shade - Full Sun
Moisture Tolerance Dry - Wet: Tolerates brief periods of standing water as well as drought once established.
Zones 4a - 7b (Usually hardy to -30° F)
Tags Attracts Bees, Attracts Butterflies, Attracts Pollinators, Attracts Wildlife, Deciduous, Deer Resistant, Drought Tolerant, Dry, Full Sun, Good for Rain Garden, Illinois Native, Medium, Native to North America, Non-Allergenic, Partial Shade, Partial Sun, Perennial, Potentially Toxic, Rabbit Resistant, Shrub, Tolerant of Clay Soil, Tolerant of Loamy Soil, Tolerant of Sandy Soil, Well-Drained Soil, Wet, Wet Site Tolerant, Winter Interest
Bloom Period Midsummer to Early Fall
Flower Color Golden Yellow
Foliage Color Blue-Green
 

More Info from Experts

Commonly Planted with...

Pairs well with other sun-loving native wetland-edge plants such as Swamp Milkweed (Asclepias incarnata), Joe Pye Weed (Eutrochium), Switchgrass (Panicum virgatum), and Blue Flag Iris (Iris versicolor), or with ornamental grasses and ferns in a rain garden setting.

Photos of This with...

Cardinal Flower
 
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Pricing and Availability History

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Past Availability
2025 : 04/13 - 10/04
2024 : 05/01 - 10/05
2023 : 05/04 - 09/10


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Field-Grown vs. Greenhouse-Grown Plants

Plants which are well-adapted to our local climate are most often field-grown (outside). Field-grown plants are generally cheaper and have the advantage of already somewhat acclimated to our cold winters, but that means they’re not artificially far along in the spring and tend to bloom at the normal time in our area.

Spring annuals and tender perennials are typically grown in Greenhouses so they can be ready and luxurious exactly when customers want them. Some perennials are also “forced” into early bloom in greenhouses. In May, there can be a very big difference between field-grown and greenhouse-grown plants of the same type. The latter typically look good right away (so they’re a great choice where that’s important), but we typically pay a premium for it.


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No Pricing or Availability Right Now

We order from a rotating cast of the best nurseries in the Great Lakes region. It looks like we've offered this plant in the past, but the nurseries we're working with this week don't appear to have it in stock at the moment.

Our goal is to bring as many plants together under "one roof" as possible, so we'll try hard to make it available again in the future!