By Josie Borlongan, Garden Guides Contributor
Wisteria is a member of the Pea family, genus Fabaceae (formerly Leguminoseae). Wisterias are hardy, vigorous ornamental vines that have the ability to climb high. They have large, pendulous flower clusters that come in white, pink, lilac, blue and purple colors. The flowers typically bloom April to June and grow best under full sun to partial shade.
Choose an area in the garden that has full sun to partial shade to plant your wisterias. They require six or more hours of direct sun per day to bloom well. Prepare your soil with a pH of 6.0 to 7.0 as they prefer the soil neutral or slightly acidic. Keep the soil moderately fertile and moist. Prepare the soil in the planting area 2 to 3 feet in diameter and 18 to 24 inches deep. Mix your soil with peat moss, compost or well rotted manure, one-third by volume, to improve soil aeration and drainage. Prepare trellises or some type of support for when they start climbing.
Wisterias bear fruits that are long, green flattened pods that are not particularly ornamental. Wisterias can be grown as bonsai. There are a number of species that are suitable for bonsai; they vary in sizes and colors.
Choosing a Variety
Wisteria sinensis or Chinese wisteria and Wisteria floribunda or Japanese wisteria are two common species of wisteria that are typically used in residential gardens. Of the two, the Chinese wisteria is the more popular one mainly because of its flowering habit that grows up to 25 feet and the clustered flowers up to 6 inches that are colored violet-blue and haveslight fragrance. The Japanese wisteria grows to a height of 25 feet or more and has violet-blue, fragrant flowers that bloom. The plant has yellow fall foliage color. American Wisteria or Wisteria frutescans and Kentucky Wisteria or Wisteria macrostachya are popular picks as well.The recommended varieties are Alba that has white flowers; Carnea that has flesh-pink flowers; Longissima that has light purple flowers with long clusters; Macrobytrys that is reddish-violet in color and flowers that cluster to 3 feet or longer; Praecox that are dwarf blue-purple in color; Purpurea that has purple flowers; Rosea that has pale rose flowers with purple tips and are 18 inches long; Rubra that has deep pink to red flowers and Violacea Plena that has reddish violet flowers.
Vines can be planted by placing the root ball of the plant in the hole 18 to 24 inches deep, spacing them 2 to 3 feet apart. If your wisteria is grafted, set it so the graft union is slightly below the soil surface. Fill in the hole with the prepared soil mix and firm it around the root ball. Soak the entire planting area with water.
Water your wisterias heavily before and during flowering. New plants will require an inch of water per week applied either through irrigation or as rainfall. After flowering, usually around summer, place the pot in a tray of water so that the plant can soak up as much water as it needs. Do not allow the water to stagnate or the roots may rot. Fertilize heavily in spring before flowering and in late summer and autumn, until the leaves drop. You can use organic and slow-acting fertilizers that can be applied following the recommended formula and intervals from the label. Use chemical fertilizers, either half strength every week or full strength every two weeks. Young plants should be fertilized annually until they fill the allotted space. Avoid applying fertilizers when the shoot and foliage growth and color is not good.Since wisterias are vigorous growers structural pruning and wiring are necessary after the blooms have disappeared. Cut off the dry racemes, leaving two to three shoots at the base of the raceme; pinch back the tender tips of these shoots. Do not remove new shoots before the end of summer anddiscourage new buds that may weaken the blooms the following spring. After August, completely remove any shoots. You may also want to remove any new seed pods as soon as they appear so as not to compete with nutrients and plant strength.