Some would consider growing wisteria for its gnarled, twining growth and graceful, green foliage alone, but then in spring it tops all this by producing a truly breathtaking display of long, pendant, scented flowers. All it needs is a little annual care.
When to Prune: Winter and summer
Time to Complete: 3 hours
Wisteria is notorious for being slow to flower, but this is only if it’s grown on its own roots. Whereas plants grown from seed may take over 10 years to start flowering, grafted ones can bloom within three or four years. The nursery or garden center should be able to reassure you about this, and you can see the graft yourself at the base of the stem, but the best way to be sure is to buy a plant in flower. The open flowers also give you the chance to decide which color you prefer.
Wisterias are big, heavy climbers, so plant them only where you have a large, sturdy support in place such as heavy-duty wires or a pergola. Prepare the soil well before planting, digging it over and mixing in plenty of organic matter. At first you may need to tie the stems loosely to their supports, but this task won’t be necessary for long because they begin to twine.
The best time to assess the overall shape of your plant is after flowering. If there are any gaps, fill these by training new stems along the support in that direction. Tie this new growth in loosely to the framework using twine.
Once stems are tied in, cut back all other growth to about 12 inches from where it sprouts. Restricting growth and allowing sunlight and air to ripen the young stems helps promote flowering the following year.
For best results, prune again in late winter. First identify any long, sappy stems that sprouted after pruning in summer, and prune them back to about five buds away from the main branch, cutting just above a bud.
Then, shorten the shoots that were pruned in the summer even farther, back to two or three buds. Look carefully for the fat, round flower buds, and avoid cutting these off. Foliage buds, which can be removed, are slimmer and pointed.
Wisteria is a vigorous plant, and its stems can become thick and woody with age. These can cause problems if they grow where they’re not wanted, so cut stems away from gutters, windows and behind pipes when you are pruning.