Ninebark (genus Physocarpus) is classified under the Rosaceae family. The most commonly cultivated species is Physocarpus opulifolius, known as common ninebark, but there are other species like Physocarpus capitatus (Pacific ninebark) and Physocarpus amurensis (Amur ninebark). The name ‘ninebark’ comes from the peeling bark that appears to have multiple layers, similar to nine layers of bark.
Physocarpus opulifolius is native to eastern North America, from Quebec to Minnesota, and south to Georgia and Oklahoma. Physocarpus capitatus is found on the west coast, from British Columbia to California. These plants are typically found in woodland edges, along streams, or in open, rocky areas where they can benefit from both sun and moisture.
Ninebark has a history of use by Native American tribes. For instance, the bark was used for medicinal purposes, such as treating various ailments including skin conditions or as an emetic. The plant’s ornamental value was recognized later, with cultivars becoming popular in landscaping for their hardy nature and aesthetic appeal, especially after the introduction of colorful foliage varieties in the 20th century.
Ninebark is a deciduous shrub that can grow up to 10 feet tall and wide, depending on the species and cultivar. It’s known for its attractive, exfoliating bark which peels in layers, revealing shades of brown, tan, and sometimes pink. The leaves vary from green to deep burgundy or copper, with some cultivars offering variegated patterns. In spring or early summer, it produces clusters of small, white or pink flowers, followed by red, berry-like fruits that attract birds.
Ninebark is adaptable to a wide range of climates, with Physocarpus opulifolius being hardy in USDA Zones 3 through 7. Pacific ninebark (Physocarpus capitatus) is suitable for Zones 5 through 9, showcasing the plant’s versatility across different temperature zones.
With proper care, ninebark can live for several decades, often reaching 20 to 30 years or more. Its longevity is enhanced by its ability to withstand various environmental stresses, including cold winters, making it a long-term investment in garden landscapes.
Landscape Uses
Ninebark is highly valued in landscaping for several reasons:
- Versatility: It can be used as a specimen plant, in mass plantings, as a hedge, or for erosion control on slopes due to its robust root system.
- Ornamental Value: The colorful foliage, particularly of cultivars like ‘Diabolo’ with its dark purple leaves or ‘Little Devil’ for smaller spaces, adds year-round interest. The peeling bark provides winter interest.
- Wildlife Attraction: The flowers attract pollinators like bees, while the berries that follow are a food source for birds.
- Privacy and Screening: Its dense growth habit makes it suitable for creating privacy screens or natural barriers.
- Low Maintenance: Ninebark is drought-tolerant once established, requires minimal pruning (though can be rejuvenated with hard pruning), and is relatively pest and disease-free.
- Soil Adaptability: It can grow in various soil types, including clay, though it prefers well-drained soil.
Ninebark Shrub: Cultivation
Selecting Species or Cultivars
Choose ninebark species or cultivars based on your local climate, available space, and desired foliage color. Common choices include Physocarpus opulifolius and its colorful varieties like ‘Diabolo’ or ‘Summer Wine’.
Planting Location
Ninebark thrives in full sun to part shade. Full sun brings out the best foliage color and flower production, but it can tolerate some shade, especially in hotter climates.
Soil Requirements
It prefers well-drained soils but is adaptable to various soil types, including clay. Ninebark can handle both acidic and alkaline conditions, making it quite versatile.
Planting Time
The best times for planting are spring or fall. This allows the plant to establish roots before facing the stress of summer heat or winter cold.
Spacing
Space plants according to their mature size; typically, 5 to 8 feet apart for larger varieties or closer for smaller cultivars, ensuring good air circulation.
Watering
Provide regular watering to young plants until they’re established. Once mature, ninebark is drought-tolerant, though occasional watering during extended dry spells can promote vigor.
Mulching
Apply a mulch layer around the base to conserve moisture, suppress weeds, and protect roots from extreme temperatures. Keep mulch away from the stem to prevent rot.
Pruning
Prune in late winter or early spring to remove dead wood, shape the plant, or rejuvenate older specimens. Some varieties benefit from thinning to improve air flow.
Fertilization
Ninebark generally doesn’t require much fertilization. If growth seems slow or foliage lacks vibrancy, use a balanced, slow-release fertilizer in spring.
Pest and Disease Control
Ninebark is relatively pest-resistant, but watch for aphids or scale. Leaf spots can occur but are usually not severe. Good sanitation and air circulation help prevent issues.
Propagation
Propagation can be done via softwood cuttings in early summer or by dividing the plant in early spring. Seeds are less commonly used due to slower growth and variability.
Winter Care
In colder zones, mulch around the base to protect the roots from frost heave. While hardy, young plants might need some protection from harsh winter winds.