Mountain laurel (Kalmia latifolia 'Ostbo Red')
Kalmia latifolia 'Ostbo Red' is a stunning broadleaf evergreen Mountain laurel prized for soft pink blooms emerging from dramatic red buds in May.
Complete Plant Information
Overview
Kalmia latifolia ‘Ostbo Red’ is a highly ornamental cultivar of Mountain laurel celebrated for its distinctive spring color display. This broadleaf evergreen provides structure and year-round interest with its dense, twisting foliage, contrasting beautifully with the spring flowers. The cultivar is specifically noted for opening brilliant red flower buds into soft pink blooms, making it a prime focal point in shaded gardens.
As a selection of the native Kalmia latifolia, this shrub thrives in woodland settings and complements other acid-loving plants. It typically matures to a manageable size, making the four-to-six-foot height perfect for framing woodland paths or serving as a substantial middle-layer specimen. Gardeners value the Mountain laurel for its resilience to deer and robust evergreen nature.
The superb spring show provided by Kalmia latifolia ‘Ostbo Red’ ensures it remains a staple where cool, moist, and slightly acidic conditions can be maintained close to its roots. Proper siting in part shade is key to maximizing flower production while protecting the sensitive leaves from harsh afternoon sun.
Fast Facts
- Plant Family: Ericaceae
- Plant Type: Broadleaf evergreen
- Hardiness Zones: USDA Zones 4-9
- Size at Maturity:
- Height: 4-6 ft
- Spread: 4-6 ft
- Bloom Time: May
- Bloom Description: Soft pink from red buds
- Sun Exposure: Part shade
- Water Needs: Medium
- Maintenance Level: Medium
How to Grow
The ideal environment for establishing Kalmia latifolia ‘Ostbo Red’ mirrors its native habitat: cool, moist, rich, acidic, and humusy soil that drains well. Planting should ideally occur in the spring or early fall, allowing the roots time to settle before temperature extremes. Raised plantings are strongly recommended, especially in areas prone to heavy clay, to ensure excellent drainage—a critical factor for the health of this Mountain laurel.
Water needs are best described as medium; consistently moist soil prevents stress, but saturated conditions must be avoided. To aid moisture retention and keep the root zones cool, apply a deep layer of mulch. While the plant tolerates a wide light range, the best performance for Kalmia latifolia ‘Ostbo Red’ involves part shade—morning sun followed by protection from intense mid-to-late afternoon heat.
Maintenance involves the timely removal of spent flower clusters immediately following the May bloom; this practice, known as deadheading, encourages more energy directed toward foliage development and next year’s buds. Pruning should be light and performed right after flowering ceases to shape the shrub and encourage bushier growth. Avoid heavy pruning later in the season.
Landscape Uses
Mountain laurel, particularly the striking ‘Ostbo Red’ cultivar, excels as a superior flowering specimen in shaded borders or mass plantings within woodland landscapes. Its dense evergreen structure makes it excellent for lending year-round privacy or acting as a foundational element near homes where it contrasts nicely with shade-loving perennials.
Consider planting groupings of Kalmia latifolia ‘Ostbo Red’ alongside companion plants that share similar cultural needs, such as rhododendrons, azaleas, and ferns. These combinations create rich layers of texture and color in woodland gardens or naturalized settings. This cultivar also works effectively as screening material or as an accent shrub where its vibrant early spring buds can be fully appreciated.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Kalmia latifolia, commonly called mountain laurel, is a gnarled, multi-stemmed, broadleaf evergreen shrub or small tree native to Eastern North America, noted for its excellent spring flowers and quality year-round foliage. The ‘Ostbo Red’ cultivar, selected for its ornamental appeal, features bright red flower buds that eventually open to soft pink flowers, maturing to 4-6 feet tall and wide over the first decade. Its glossy, dark green leaves are smaller and twist more than those of the species plants.
Tolerances
- Rabbit
- Deer
Potential Problems
Mountain laurel (Kalmia latifolia) can be susceptible to certain fungal issues, including leaf spots and blights, which often manifest during overly humid or wet periods. Furthermore, horticultural pests such as borers, scale insects, whiteflies, and lace bugs can attack stressed plants.
Prevention involves ensuring good air circulation through proper spacing and pruning, and maintaining consistent soil moisture without water logging. Inspect foliage regularly, especially in spring and summer, and promptly address infestations with horticultural oils or appropriate treatments for scale or lace bugs before they become severe.
Frequently Asked Questions
What hardiness zones is Mountain laurel suitable for?
This cultivar, Kalmia latifolia ‘Ostbo Red’, is hardy and adaptable across USDA Zones 4 through 9.
How large does Kalmia latifolia ‘Ostbo Red’ grow?
It typically reaches a mature height between 4 and 6 feet tall and spreads to a similar width of 4 to 6 feet.
What sun exposure does Mountain laurel need?
This plant performs best when situated in part shade, although it can tolerate everything from full sun to full shade depending on the intensity of the local climate.
When does Kalmia latifolia ‘Ostbo Red’ bloom?
The bloom time is generally in May, presenting the characteristic light show of soft pink flowers emerging from their ornamental red buds.
Conclusion
The Kalmia latifolia ‘Ostbo Red’ offers gardeners a fantastic opportunity to introduce reliable evergreen structure punctuated by one of the most beautiful spring flower displays in the woodland garden. Its deer resistance combined with the unique red-to-pink bud transitions makes this Mountain laurel a highly rewarding choice. Before planting, confirm your site provides the necessary acidic, well-drained soil and protection from harsh afternoon sun to ensure the best health for your new shrub.
Companion Planting
Since Mountain laurel thrives in acidic soil, companion planting should focus on other acid-lovers. Azaleas and rhododendrons are classic partners, offering sequential blooms and similar foliage texture. Underplanting with acid-tolerant perennials like bleeding hearts, ferns, or woodland phlox will help stabilize soil moisture and complement the shrub’s mid-story presence.
Seasonal Care Calendar
Spring care should focus on routine cleanup and preparing for the bloom flush. In early spring, apply a loose layer of pine needle mulch to maintain soil temperature and acidity. Immediately after the May bloom finishes, deadhead spent clusters to direct energy toward strong summer growth. During hot, dry periods, ensure deep, consistent watering as the Mountain laurel dislikes drying out completely during the growing season.
