St. John's wort (Hypericum frondosum 'Sunburst')
Hypericum frondosum 'Sunburst' St. John's wort is a dense shrub noted for large yellow flowers and attractive blue-green foliage, thriving in zones 5-8.
Complete Plant Information
Overview
Hypericum frondosum ‘Sunburst’ is a standout deciduous shrub cherished for its striking visual contrast, featuring brilliant golden yellow flowers set against attractive blue-green foliage. This variety of St. John’s wort maintains a compact, mounded habit, making it highly versatile in diverse landscape settings. It provides excellent seasonal interest, moving from bright summer blooms to persistent reddish-brown fruit capsules that last into winter.
This resilient shrub is generally easy to cultivate, requiring only average, well-drained soils and preferring full sun to partial afternoon shade. While it is noted for being somewhat drought-tolerant once established, its primary ornamental value comes from its easy-going nature and low maintenance requirements for the dedicated gardener. The specific cultivar ‘Sunburst’ often exhibits slightly larger flowers than the straight species.
As a foundational planting or hedge element, Hypericum frondosum ‘Sunburst’ offers reliable structure and color. Gardeners appreciate that even if winter weather causes dieback in colder zones, healthy roots frequently survive to send up new flowering shoots, as blooms appear reliably on new wood.
Fast Facts
- Plant Family: Hypericaceae
- Plant Type: Deciduous shrub
- Hardiness Zones: USDA Zones 5-8
- Size at Maturity:
- Height: 3-4 ft
- Spread: 3-4 ft
- Bloom Time: June to July
- Bloom Description: Yellow
- Sun Exposure: Full sun to part shade
- Water Needs: Medium
- Maintenance Level: Low
How to Grow
Planting Hypericum frondosum ‘Sunburst’ is best accomplished in spring or fall, establishing the root system before extreme summer or winter stress hits. This St. John’s wort thrives in average, medium, well-drained soils, though it shows a preference for rich, sandy loam. Ensure the site offers full sun exposure for the best flowering, though it tolerates light afternoon shade.
Water needs are medium; established plants demonstrate good drought tolerance. However, consistent moisture during the first growing season is crucial for proper establishment. Fertilization is usually unnecessary if the soil is reasonably fertile; avoid high-nitrogen fertilizers which can promote excessive, soft foliage growth at the expense of flowers.
Pruning is primarily aesthetic or corrective. In areas where winter dieback is common (such as the northern edge of its range), you can cut the entire plant back hard in early spring if necessary, as flowers bloom on new wood. Mulching the roots in winter is a helpful practice to mitigate temperature fluctuations and conserve moisture for this dependable shrub.
Landscape Uses
Hypericum frondosum ‘Sunburst’ excels in landscape roles requiring consistent texture and moderate height. Due to its upright, mounded shape, it functions perfectly as a neat, low hedge or as an informal border plant along pathways. Its ability to hold its form makes it suitable for foundation plantings where year-round structure is desired, although gardeners must account for potential winter tip damage in colder microclimates.
Massing several Hypericum frondosum ‘Sunburst’ shrubs together creates a stunning, continuous display of golden color during mid-summer. For companion planting, pair this St. John’s wort with perennials that offer late-season interest, such as Sedum or ornamental grasses, to balance the garden as the Hypericum blooms fade. It provides excellent complementary texture against fine-leaved evergreens.
Standout Features
Flower Qualities
- Showy
Fruit Qualities
- Showy
Noteworthy Characteristics
Hypericum frondosum is a small, dense, upright, mounded deciduous shrub that is noted for its large showy golden yellow flowers and attractive blue-green foliage, growing to 3-4’ tall and as wide. It features solitary, bright yellow 5-petaled flowers up to 2” in diameter on the ‘Sunburst’ cultivar, which bloom profusely in June and July. Mature stems develop attractive exfoliating reddish-brown to purplish bark that adds winter interest to the landscape.
Tolerances
- Drought
Potential Problems
Wilt and root rot are significant concerns for this St. John’s wort, especially when the plant is situated in hot and humid southern climates. These issues are often exacerbated by poorly draining soils, so amending heavy clay with sand or organic matter is essential for success. Susceptibility to nematodes is also noted, which can cause root damage mimicking root rot symptoms. Prevention centers on proper site selection: prioritize well-drained locations and avoid excessive overhead watering that keeps foliage wet for long periods. Leaf spot, mildew, and rust are generally less threatening diseases.
Frequently Asked Questions
What hardiness zones is St. John’s wort suitable for?
The Hypericum frondosum ‘Sunburst’ is reliably hardy in USDA Zones 5 through 8.
How large does Hypericum frondosum ‘Sunburst’ grow?
This compact cultivar typically reaches a mature height and spread of 3 to 4 feet tall and 3 to 4 feet wide.
When does St. John’s wort bloom?
Hypericum frondosum ‘Sunburst’ produces its signature display of bright yellow flowers primarily from June into July.
What sun exposure does Hypericum frondosum ‘Sunburst’ need?
For the best flowering and most compact form, plant this St. John’s wort in a location receiving full sun to an area receiving light part shade.
Conclusion
The Hypericum frondosum ‘Sunburst’ offers exceptional value through its vibrant golden summer blooms and tough, low-maintenance nature. This specific St. John’s wort variety adds excellent texture with its blue-green leaves and exfoliating bark, providing multi-season appeal. Before planting, always confirm that your local USDA zone falls within the 5 to 8 range for optimal performance.
Companion Planting
Selecting companions that share medium water needs and thrive in similar sun conditions will ensure the best health for your Hypericum frondosum ‘Sunburst’. Consider pairing it with plants that provide contrasting foliage textures, such as fine-bladed ornamental grasses or groundcovers that offer blooms either before or after the summer peak of the St. John’s wort. Successful pairings often include spring-flowering bulbs that die back before the shrub fully leafs out, maximizing the utility of the planting space.
Design Ideas
The sturdy, mounded habit of the ‘Sunburst’ cultivar makes it excellent for softening architectural lines when used near foundations, provided there is sufficient air circulation to mitigate humidity issues. For a naturalistic, cottage garden feel, intermingle these shrubs among native meadow perennials suitable for rocky or limestone soils, reflecting its native habitat. Since the bark exfoliates beautifully, consider placing the shrub where its lower stems are visible, perhaps backed by dark green evergreens that allow the reddish-brown winter color to truly stand out.
