By: Darcy Larum, Landscape Designer
Wisteria is a classic, deciduous vine, beloved for its large drooping clusters of fragrant pea-like flowers and quick growth habit. Wisteria fits in nicely in cottage gardens, Zen/Chinese gardens, formal gardens, and can even do well in xeriscape gardens once they are established. There are approximately ten different species of wisteria, native to China, Korea, Japan and the eastern United States.
While not all of these species are commonly found in garden centers or online nurseries, many new species and cultivars are easily available. Chinese wisteria (Wisteria sinensis) and Japanese wisteria (Wisteria floribunda) are two of the most popular species of wisteria for the landscape. However, in this article we will discuss the lessor known, Silky wisteria (Wisteria brachybotrys syn. Wisteria venusta).
Silky wisteria is native to Japan. However, it is not classified as Japanese wisteria because it has characteristics that make it quite different than the species commonly known as Japanese wisteria. The foliage of silky wisteria is covered in silky or downy hairs, which accounts for its common name. While Japanese wisteria has long flower racemes, silky wisteria’s racemes are only 4-6 inches (10-15 cm.) long.
Silky wisteria plants are hardy in zones 5-10. They bloom from mid-spring to mid-summer. The violet-lavender blooms are highly fragrant and attract bees, butterflies and birds to the garden. From a distance, wisteria flower racemes look like clusters of grapes. Up close, the small flowers are similar to pea flowers.
When the flowers fade, wisteria produces pea-like seed pods, and these seeds can be toxic if ingested. When propagated by seed, silky wisteria plants may take 5-10 years before they produce blooms. However, wisteria plants usually produce more and more blooms with each year they age.
Silky wisteria vines grow best in full sun to part shade. They will tolerate poor soil but prefer moist loam. Fertilize silky wisteria plants in spring, with a low nitrogen fertilizer. Wisteria plants have nitrogen fixing properties, so adding nitrogen to them is not necessary. They will, however, benefit from added potassium and phosphorus.
Silky wisteria plants are a fast growing deciduous vine, growing up to 40 feet (12 m.) long. Silky wisteria vines will quickly cover a pergola, arbor, or trellis. They can also be trained to grow in the form of a tree. Wisteria can be pruned after blooming to control its growth.
Some popular varieties of silky wisteria plants are:
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Successful gardens provide visual interest both vertically and horizontally. Most plants grow primarily vertically, but you can achieve variety by growing plants that naturally spread horizontally. Do this by placing support structures that encourage plants to grow vertically and by pruning to achieve a horizontal effect. Moreover, certain design strategies can highlight the horizontal features of some plants and add a horizontal effect to your garden.
When planting this vine, pick a spot where you can fit a solid support structure, such as an arbor or a pergola, that will be able to carry the weight of the plant once it's mature. To train wisteria vines, choose a single upright stem to attach to your support. Then, religiously remove any side shoots as they appear, forcing the plant into upward growth. Pruned correctly, the wisteria will form a beautiful overhead shade canopy. Once the plant reaches the height you want, continuously prune the tips of the plant to stunt further growth.
If you have trouble getting the vines to flower, there are several methods you can use. For instance, you can apply a high-phosphorus fertilizer, which can promote blooming. You also can try heavily pruning the plant right after it blooms and again in the winter to encourage more buds.
Wisteria can be subject to leaf-chewing insects, but the damage is rarely serious. There are no notable disease issues. But these are high-maintenance plants due to the need for diligent pruning. Be prepared to keep it tamed if you plant this species in your garden.
Many wisteria species prefer lots of sun, but Chinese wisteria can tolerate some shade. However, the best flowering occurs when the plant gets partial to full sun.
Chinese wisteria likes humusy, moderately fertile, and slightly acidic soil. Good drainage is key for the plant. Make sure the soil in your growing site fits the bill for this plant because it dislikes being transplanted.
Water a young plant deeply and frequently to help develop its root system, though you should never allow it to sit in soggy soil. Once established, the vine prefers even moisture via rainfall and regular watering, but it can tolerate a little drought.
Chinese wisteria can withstand temperatures down to around minus 20 degrees Fahrenheit. But its buds might die in prolonged cold, causing the plant to flower less. This plant likes high humidity but can grow in drier climates as long as its soil remains moist.
Fertilizer usually is unnecessary for Chinese wisteria unless your soil is deficient in nutrients. A layer of compost can be an effective way to promote growth and blooming.
Other Names: Rehsonia brachybotrys
An elegant flowering vine, with exquisite chains of pure white flowers tipped yellow that cascade from the stems in spring can grow quite woody, needs ample support, best if grown on a structure vulnerable to late spring frost damage to flower buds
Shiro Kapitan Silky Wisteria is draped in stunning chains of fragrant white pea-like flowers with a yellow blotch hanging below the branches from early to mid spring. It has green foliage throughout the season. The fuzzy narrow compound leaves do not develop any appreciable fall color. The fruit is not ornamentally significant.
Shiro Kapitan Silky Wisteria is a multi-stemmed deciduous woody vine with a twining and trailing habit of growth. Its average texture blends into the landscape, but can be balanced by one or two finer or coarser trees or shrubs for an effective composition.
This is a high maintenance woody vine that will require regular care and upkeep, and should only be pruned after flowering to avoid removing any of the current season's flowers. It is a good choice for attracting hummingbirds to your yard, but is not particularly attractive to deer who tend to leave it alone in favor of tastier treats. Gardeners should be aware of the following characteristic(s) that may warrant special consideration
Shiro Kapitan Silky Wisteria is recommended for the following landscape applications
Shiro Kapitan Silky Wisteria will grow to be about 25 feet tall at maturity, with a spread of 24 inches. As a climbing vine, it tends to be leggy near the base and should be underplanted with low-growing facer plants. It should be planted near a fence, trellis or other landscape structure where it can be trained to grow upwards on it, or allowed to trail off a retaining wall or slope. It grows at a fast rate, and under ideal conditions can be expected to live for approximately 30 years.
This woody vine should only be grown in full sunlight. It does best in average to evenly moist conditions, but will not tolerate standing water. It is not particular as to soil type or pH. It is highly tolerant of urban pollution and will even thrive in inner city environments. Consider applying a thick mulch around the root zone in winter to protect it in exposed locations or colder microclimates. This is a selected variety of a species not originally from North America, and parts of it are known to be toxic to humans and animals, so care should be exercised in planting it around children and pets.
'Prolific' is a Chinese wisteria named for its many spring lilac-purple flowers. It often flowers at an earlier age and with greater abundance than other varieties. 'Purple Patches' sets 3-foot-long flower clusters. 'Okayama Silky' has rich violet flowers with a strong pleasing perfume.
Wisteria macrostachya 'Blue Moon' is an extra-hardy selection with clusters of silvery-blue flowers in late spring and often again in summer. It climbs to 25 feet. Zones 4-9
Wisteria floribunda 'Honbeni' sets clusters of pink flowers in late spring. It climbs to 30 feet. Zones 5-9
Wisteria floribunda 'Alba' bears clusters of pure-white flowers in late spring. It climbs to 30 feet. Zones 5-9