Wisteria is a deciduous climbing vine related to the pea family, according to Jane C. Martin of the Ohio State University Extension. When properly cared for, wisteria vines bloom extravagantly in the spring, producing clusters of fragrant pink, white or lavender flowers that can be a foot long. Wisterias are valuable landscaping plants because they can be trained and shaped into shrubs, vines or trees. They are tough and versatile, but do require conscientious pruning.
Choose a site for your wisteria that gets at least six hours daily of direct sunlight, and where there’s no danger of the vine’s stems invading the gutters of any nearby buildings.
Install the support for your wisteria. You can buy prefabricated pergolas, trellises or arbors and install them according to the manufacturer’s directions, or build and install your own. If you choose to do the latter, use metal that won’t rust (like copper or aluminum) or pressure-treated wood.
Be sure that your support is sturdy and installed so that it won’t buckle under the weight of the wisteria vine as it matures. If you prefer, build a support on a wall by stringing several rows of heavy wire horizontally along it, about 4 to 6 inches out from the wall. Leave about 18 inches of space between each row of wire.
Prepare the soil by digging out an area 2 to 3 feet wide and 18 inches to 2 feet deep. Mix the soil with compost, rotted manure or peat moss, so that the resulting mixture is two-thirds soil to one-third additives. This lightens the soil and improves drainage.
Set the wisteria vine into the prepared hole so that the top of the root ball is several inches below the surface of the soil. If yours is a grafted wisteria, look for the place on the trunk of the vine where the graft took place, and place the vine so that the graft union is an inch or so below the soil. Fill in the hole below and around the vine and press down firmly.
Water the wisteria vine thoroughly—really soak it. Martin says that young plants need an inch of water per week while they are establishing themselves.
Fertilize your young wisteria every year, until it has grown into the space you’ve set aside for it.
Pick a single upright healthy stem to be the main “leader” and tie it to your support with twine or garden tape. Prune off all the other side shoots to manage the growth of your wisteria vine.
Keep training the main leader as it grows up the support till it reaches the height you want. Then prune off the top of the leader.
As side shoots grow out from the main leader, direct them outward from the central stem along the lateral parts of the support.
Prune the stems that grow from the side branches just beyond the sixth or seventh leaf each summer. The pruned stems will then put out more shoots; prune them back as soon as they’ve produced one or two leaves. All this pruning will encourage the vine to fill in its space and to flower more profusely.
Prune any shoots growing on the main leader back by one-half to two-thirds of their length In the early winter. Cut back the side shoots that you pruned in the summertime so that they’re only an inch or two long. Flowers will develop on these short stems.
Continue to prune the vine as described each summer. Each winter, cut back any leader shoots so that there are only four or five buds on each one. Keep removing any suckers or side shoots that develop on the main leader, to keep it straight and clean.