Wisteria is a genus of flowering plants in the legume family, Fabaceae. The genus includes four species of woody twining vines that are native to China, Japan, Korea, Vietnam, southern Canada, the Eastern United States, and north of Iran. They were later introduced to France, Germany and various other countries in Europe. Some species are popular ornamental plants. The genus name is also used as the English name, and may then be spelt ‘wistaria’.
Wisteria plants are vigorous, woody vines that can grow very quickly, often reaching up to 30 feet or more in height and width without pruning. This vigorous growth can make them somewhat invasive if not properly managed. The vines twist around their supports for climbing. Asian Wisterias (like Wisteria sinensis and Wisteria floribunda) twist clockwise, while the American variety (Wisteria frutescens) tends to twist counterclockwise.
Wisteria is famous for its long, hanging clusters of flowers, known as racemes. These can grow from a few inches to several feet long, depending on the species and variety. Wisteria flowers are shades of purple or blue, but they can also be white, pink, or even yellow in some species or cultivars. Many varieties have a strong, sweet fragrance that can fill the air around the plant, attracting bees, butterflies, and other pollinators.
Most wisterias bloom in late spring, although flowering times can vary by species. Some cultivars might bloom again in summer or fall, but the primary bloom is in spring. The bloom period can last from about two weeks to a month, depending on the weather conditions. Wisteria can be slow to start blooming if grown from seed, often taking years, which is why grafting or layering is preferred for quicker flowering. They also need regular pruning to keep them from becoming unmanageable or invasive.
Characteristics
Wisteria sinensis (Chinese Wisteria)
- Origin: China
- Characteristics: This is one of the most common wisterias in gardens. It’s known for its fast growth and can become invasive. The flowers are generally lilac-blue, though white and pink varieties exist. They bloom in late spring, producing fragrant, pea-like flowers in long racemes up to 18 inches. The vines twist clockwise.
Wisteria floribunda (Japanese Wisteria)
- Origin: Japan
- Characteristics: Known for its slightly later blooming than Chinese wisteria, often in late spring to early summer. It has elongated flower clusters that can grow up to 3 feet long, with a wide color range including blues, pinks, purples, and whites. The vines twist counterclockwise.
Wisteria brachybotrys (Silky Wisteria)
- Origin: Japan
- Characteristics: This species has shorter, but very fragrant flower clusters. The flowers are silky to the touch due to the fine hairs on the petals. Varieties like ‘Shiro Kapitan’ have white flowers, while ‘Okayama’ has dark violet blooms.
Wisteria frutescens (American Wisteria)
- Origin: Eastern North America
- Characteristics: Native to the southeastern United States, this wisteria is less aggressive than its Asian counterparts. Flowers are typically bluish-purple, shorter than Asian types, and bloom in mid to late spring. It’s also known for not twining around supports but climbing by tendrils.
Wisteria macrostachya (Kentucky Wisteria)
- Origin: United States (Kentucky, Tennessee)
- Characteristics: Similar to American wisteria but with longer flower clusters. ‘Blue Moon’ is a notable cultivar that blooms up to three times in a season.
Wisteria venusta (Silky Wisteria)
- Origin: Japan
- Characteristics: Another Japanese species with particularly fragrant flowers, this wisteria has a silky texture to its blooms, similar to W. brachybotrys but with a different growth habit.
Cultivation
Cultural Requirements
- Sunlight: Requires full sun to partial shade for best flowering. Too much shade can result in fewer blooms.
- Soil: Prefers well-drained, fertile soil. While they can adapt to various soil types, they thrive best in loamy, slightly acidic to neutral pH soils.
- Support: Needs strong, sturdy support structures like arbors, pergolas, or trellises due to their heavy growth and the weight of the flowers.
Maintenance
- Pruning: Regular and sometimes aggressive pruning is necessary. Pruning not only controls the size but also encourages flowering, as flowers are more likely to form on new wood. Winter pruning shapes the plant, while summer pruning controls the length of new growth.
- Training: Training young plants to grow in the desired direction is crucial. This involves tying or directing the vines when they are still pliable.
Potential Issues
- Invasiveness: Without proper pruning, wisteria can become invasive, covering trees or structures and even damaging buildings or displacing native plants if it escapes into the wild.
- Slow to Bloom: Wisterias grown from seed can take several years to produce flowers for the first time, often delayed by excessive vegetative growth. Grafting or choosing already mature plants can speed up this process.