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Why Be Concerned:

A wisteria may take several years to mature before flowering. Plants grown from seeds or offshoots can take up to ten years or more to flower.

Benefits:

With proper selection and care gardeners will be rewarded with a profusion of beautiful flowers each year.

How to Do It:

Following are recommended strategies.

• Selection: The best guarantee of a flowering wisteria is to select a specimen in bloom at the nursery, at the time of purchase. Buy a good selection known for its floriferous habits such as Wisteria floribunda 'Black Dragon” or W. x formosa 'Issai'. A cutting from a reliable bloomer is another possible source.
• Pruning: Wisteria may be reluctant to flower unless vigorous, leafy summer shoots are severely curtailed and the plant's energies diverted into producing flower buds. Flowering is also improved if the main stems are trained horizontally rather than vertically. The flower buds are produced on short spurs and the aim of pruning is to encourage these spurs to develop along the framework branches of an established plant.
  The simplest method is to carry out a two-stage pruning regime. The vine requires hard pruning twice annually; in July or August the new leafy shoots should be pruned back to 6 - 9 inches or 15 - 22cms and then, in very early spring or late winter, after the last severe frost, the previously pruned new shoots should be pruned back to the second or third bud. These shortened shoots will become flowering spurs.
• Root Pruning: Root pruning might also be considered if other methods fail. A mature wisteria, that is reluctant to flower, may be shocked into action by root pruning in early spring. Drive a sharp spade vertically into the soil around the wisteria at a radius of about two feet from the main stem.
• Fertilizing: In spring, feed the plant with superphosphate, following the recommended application rate on the label. Keep the plant well away from lawns that might be fertilized with high nitrogen content fertilizers. The plant will produce lush foliage at the expense of blooms.

Cautions/Considerations:

Make sure to plant the wisteria in a location that will meet its cultural needs: Plant Wisterias in a sheltered location such as against the brick wall of a house away from the worst of the winter winds. Wisterias are hardy to Zone 4; however, the buds are susceptible to cold and may be nipped by a late frost. If you live north of Zone 5, consider planting Wisteria in a sheltered spot to help protect the plant.

The upper part of the plant requires full sun (at least 6 hours). Wisterias prefer a moist, well drained, neutral, cool, loamy soil. It is recommended that the soil be amended if alkaline or calcareous.

References:

• The Toronto Botanical Garden Weston Family Library is an excellent source for horticultural information.
• Kindersley, Dorling ed. The Royal Horticultural Society Encyclopedia of Gardening. London, England: RHS, 1992.
• Hillier, Arthur. Hilliers Manual of Trees and Shrubs (Revised). Newton Abbot, U.K.: 2002.
• Cutler, Karen Davis ed. Vines [A Harrowsmith Gardener's Guide, Vol. 6]. Ontario, Canada: Camden House, 1992.

Factsheets are produced by the Toronto Master Gardeners in association with the Toronto Botanical Garden. They provide introductory information about a broad range of horticultural topics and are intended for personal use and study purposes. Should your gardening group or organization wish to use multiple copies we ask that you inform the Toronto Botanical Garden at info@torontobotanicalgarden.ca.

Date revised: January 8, 2006