St. John's wort (Hypericum kalmianum 'Deppe' SUNNY BOULEVARD)

Overview

Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD offers gardeners a durable, compact option within the St. John’s wort family. This cultivar is prized for maintaining a dense, neat mound, making it highly versatile in defined landscape settings. It reliably produces cheerful, five-petaled golden-yellow flowers throughout the peak summer months, adding significant late-season color interest.

As a tough deciduous shrub native to the Great Lakes region, this selection of Kalm St. John’s wort thrives in a variety of challenging conditions once established. Its dark green foliage and upright branching contribute to its tidy appearance, minimizing the need for constant intervention. Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD is an excellent choice for providing dependable structure and summer brightness without demanding intensive care.

Fast Facts

• Plant Family: Hypericaceae
• Plant Type: Deciduous shrub
• Hardiness Zones: USDA Zones 4-8
• Size at Maturity:
  • Height: 2-3 ft
  • Spread: 2-4 ft
• Bloom Time: July to August
• Bloom Description: Yellow
• Sun Exposure: Full sun to part shade
• Water Needs: Medium
• Maintenance Level: Low

How to Grow

Plant Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD in the spring or fall for best establishment, ensuring it receives full sun to partial afternoon shade. While it easily adapts to average, medium-moisture, well-drained soils, it particularly favors moist, rich, sandy loams. Excellent drainage is crucial to prevent root issues, though established plants show good drought tolerance.

Water deeply and regularly while the shrub is establishing its root system during the first year. Once mature, supplement water during extended dry periods, aligning with its medium water needs. Due to its low maintenance nature, fertilization is rarely necessary unless the soil is extremely poor.

Pruning should be done selectively, if needed, immediately following the bloom period in late summer. Avoid cutting back late in the season, as this may remove potential winter interest or buds for the following year. This care routine ensures the compact, mounding form of Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD remains tidy.

Landscape Uses

The compact size of Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD makes it an ideal candidate for low hedge applications, providing year-round structure defined by its dense habit. It excels when used as an edging plant along pathways or in the front of mixed shrub borders where its summer blooms can shine. This St. John’s wort variety is also perfectly suited for rock gardens or naturalized areas, particularly near pond peripheries where moisture is readily available.

Consider planting it alongside later-blooming perennials or plants that offer contrasting foliage color, such as blues or silvers, to highlight the bright yellow flowers. It fits seamlessly into wild garden designs or woodland margins, requiring minimal supplemental care once sited appropriately. Using Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD in these settings capitalizes on its inherent toughness and manageable size.

Standout Features

Flower Qualities

• Showy

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.

Tolerances

Potential Problems

This variety of St. John’s wort generally presents no serious insect or disease problems for gardeners. Its robust nature makes it a reliable performer in landscapes that match its cultural requirements. Monitor plants for common aphids if stressed, although infestations are typically minor and rarely require intervention.

Avoid overwatering, especially in heavy clay soils, as this is the primary stressor that can lead to root rot or general decline in many Hypericum species. If pruning is necessary for shaping, ensure it is done immediately post-bloom to maintain the best flowering display next season.

Frequently Asked Questions

What hardiness zones is Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD suitable for?

This tough plant is suitable for USDA Zones 4 through 8, offering adaptability across broad regions.

How large does St. John’s wort grow?

The ‘Deppe’ selection typically matures to a compact height between 2 and 3 feet tall, with spreads ranging from 2 to 4 feet wide.

When does St. John’s wort bloom?

Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD provides vibrant color when it blooms, typically from July through August, offering lovely yellow flowers.

What sun exposure does the plant need?

This shrub prefers full sun but will tolerate part shade, making it adaptable to various light conditions in the garden.

Conclusion

Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD is a standout choice for low-maintenance structure and dependable summer color in the garden. Its compact, uniform shape combined with its resilience makes this St. John’s wort an invaluable asset for borders and hedges. Check your local hardiness zone compatibility before purchasing to ensure this excellent shrub performs optimally for you.

Companion Planting

Selecting the right companions enhances the visual appeal and ecological function of your Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD grouping. Look for plants that bloom before or after mid-summer to ensure season-long interest near your St. John’s wort. Plants that appreciate similar well-drained, average to moist soils work best.

Consider pairing the bright yellow blooms with silvery foliage plants like Artemisia or contrasting deep purple flowers such as Nepeta or Salvia for high visual impact. Because this shrub is relatively low-growing and mounding, place taller grasses or perennials behind it to create depth in the border design.

Wildlife Benefits

Like many members of the Hypericaceae family, the flowers of Hypericum kalmianum ‘Deppe’ SUNNY BOULEVARD are attractive to generalist pollinators actively foraging in the mid-summer heat. The distinctive boss of yellow stamens provides an easily accessible pollen source for various beneficial insects.

While not primary nectar sources for specialist bees, the abundant summer blooms support robust pollinator activity during a period when other flowering species may be slowing down. Establishing native shrubs like this St. John’s wort helps support local insect biodiversity.