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Kalm's St. John's Wort

Hypericum kalmianum

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Kalm's St. John's Wort (Hypericum kalmianum) at Connon Nurseries

Kalm's St. John's Wort flowers

Kalm's St. John's Wort flowers

(Photo courtesy of NetPS Plant Finder)

Kalm's St. John's Wort (Hypericum kalmianum) at Connon Nurseries

Kalm's St. John's Wort in bloom

Kalm's St. John's Wort in bloom

(Photo courtesy of NetPS Plant Finder)

Height:  24 inches

Spread:  3 feet

Sunlight:  full sun  partial shade 

Hardiness Zone:  4a

Description:

An attractive and very colorful small shrub with eye-catching bright yellow flowers in mid summer and a neat, rounded form; a very versatile garden plant

Ornamental Features

Kalm's St. John's Wort is smothered in stunning yellow flowers along the branches in mid summer. The flowers are excellent for cutting. It has bluish-green foliage throughout the season. The narrow leaves do not develop any appreciable fall colour. The fruit is not ornamentally significant.

Landscape Attributes

Kalm's St. John's Wort is a multi-stemmed deciduous shrub with a ground-hugging habit of growth. Its relatively fine texture sets it apart from other landscape plants with less refined foliage.

This is a relatively low maintenance shrub, and should only be pruned after flowering to avoid removing any of the current season's flowers. It has no significant negative characteristics.

Kalm's St. John's Wort is recommended for the following landscape applications;

  • Mass Planting
  • General Garden Use
  • Groundcover
  • Naturalizing And Woodland Gardens
  • Container Planting

Planting & Growing

Kalm's St. John's Wort will grow to be about 24 inches tall at maturity, with a spread of 3 feet. It tends to fill out right to the ground and therefore doesn't necessarily require facer plants in front. It grows at a slow rate, and under ideal conditions can be expected to live for approximately 20 years.

This shrub does best in full sun to partial shade. It prefers to grow in average to dry locations, and dislikes excessive moisture. It is considered to be drought-tolerant, and thus makes an ideal choice for a low-water garden or xeriscape application. It is not particular as to soil type or pH. It is highly tolerant of urban pollution and will even thrive in inner city environments. This species is native to parts of North America.

Kalm's St. John's Wort makes a fine choice for the outdoor landscape, but it is also well-suited for use in outdoor pots and containers. Because of its spreading habit of growth, it is ideally suited for use as a 'spiller' in the 'spiller-thriller-filler' container combination; plant it near the edges where it can spill gracefully over the pot. Note that when grown in a container, it may not perform exactly as indicated on the tag - this is to be expected. Also note that when growing plants in outdoor containers and baskets, they may require more frequent waterings than they would in the yard or garden.

 
 
Hardiness Zone Plant Height Minimum Sunlight
Characteristics
Massing  Garden  Groundcover  Naturalizing  Container 
Applications
Flowers 
Ornamental Features