Wisteria is a climbing vine with most varieties producing blue flowers. It needs a support of some type and can grow up to 10 feet a year when well-established. A variety called 'Blue Moon' is hardy and will bloom from June throughout the summer. Wisteria is a member of the pea family.
Blue wisteria has a tendency to put out only vegetative growth for its first few years of life. It can be trained to grow as a vine or in a tree-shape, as long as it is supported by a trellis or post. Wisteria can even be trained to grow as a shrub if it is thinned by pruning several times during the growing season. The flowers grow in large clusters that hang down from the vines in early spring. Established blue wisteria vines often have a thick, woody trunk with an apparent twist, which is indicative of the way it climbs by twining around its support structure.
Plant wisteria in full sun and fertile soil that stays consistently moist. Wisteria prefers a neutral to slightly acidic soil with a pH of 6 to 7. Provide an arbor or trellis for it to climb upon. Do not allow it to climb upon a building as it can invade rain gutters and clog them.
Test the soil at the planting site to determine if you need to make adjustments to the pH level. Have the soil tested by your County Extension Agent, who can recommend the amendments necessary to correct the pH level. When planting, add peat moss and compost in one third of the volume of the soil removed from the planting hole to improve the structure of the soil. This will help it retain water and improve the ability of the roots to easily penetrate the soil.
Planting, Care and Cultivation
Plant wisteria so that it is growing at the same level that it was growing in its nursery pot. Set any graft union so that it is just below the surface of the soil. Back fill the hole with the improved soil, firming gently with your foot as you go. Water well after planting and provide with the equivalent of an inch of rainfall per week for the first year it is in your garden. Fertilize every spring with granulated fertilizer until the vine begins regular blooming, then fertilize only if growth is lackluster with a sickly green color.
Pruning and Training
Choose a strong and vigorous upright stem for the central or main leader of the plant. Attach it to the support structure and remove all other shoots. Side branches will develop along the central leader. Choose a pair of side branches, one on either side of the central leader, about every 18 inches along the main stem as it grows. When the main or central leader reaches the height of the support structure, cut off the growing point.
Wrap the side branches around the support as they grow. Cut off side shoots that grow from the side branches after six or seven leaves develop. Another set of shoots will grow from these pruning cuts, which should be cut back after they develop two leaves.