Training A Wisteria Tree
Training a Wisteria vine to a tree form isn't that hard to do. That said, after staking the vine there will be some needed pruning to form the tree. For best results, I suggest starting with a young vine that was grown in a 1 to 5 gallon size nursery pot and follow the basic instructions below.
Step 1
Start by planting your Wisteria vine. Find instructions under the Planting & Care Advice tab on this Wisteria page.
Step 2
After planting the vine, install a 4 x 4 wooden post or a metal fence post to a depth of at least 12 to 18 inches in the ground with 4 to 5 feet or so of the post above ground. Depending on the size/diameter of the root ball of the plant, position the post about 3 to 6 inches away from where the base of the vine. The height of the post above the ground should be a foot higher than where you will want the base of the canopy of your Wisteria tree to start above ground.
Step 3
If there is more than one stem on your vine, select the most vigorous main stem of the wisteria to become the tree's single trunk. Using pruners, remove any side shoots that are growing off of this main stem. Be careful when pruning off these side shoots that you don't gouge the main stem.
Step 4
Place the stem in a straight and vertical line up against the side of the post and tie it to the post using tie tape, cloth or other soft material. Starting from the ground up, tie the stem to the post about every 8 to 10 inches. Whatever you use as a tie, tie it tight enough to secure the vine but loose enough to allow for some movement and future growth and expansion of the main stem. If there is a side shoot growing off of the top of the main stem of your vine tie just above that branch and around the post.
Note: If your starter vine is shorter than the top of your post, allow the main stem/trunk time to grow to the top of the post, tying it every 8 to 10 inches or so as it grows up the post. As the your vine grows, continue to cut off any side shoots that emerge from the main stem. Also, as your vine grows, adjust any ties that have become too tight around the main stem so that they are somewhat loose.
When your vine grows to a foot or so above the top of the post, cut off the top of the main stem at a point just above the top of the post. Make your cut just above a growth bud on the main stem. Side shoots will emerge from this and make another bud below it that will grow and begin to develop the canopy of your Wisteria tree.
Step 7
As these side shoots (lateral branches) grow, when they have developed six leaves make a cut on this shoot that is just above the sixth leaf. New shoots will emerge at the point of this cut that will further develop the canopy of your tree.
In following years...
While your Wisteria tree is still dormant in late winter, prune out any dead, crossing or crowded branches. Immediately following bloom, prune back all side shoots in the tree's canopy to a length of 12 inches. Continue to check ties and loosen any that have become too tight around the trunk.
Hope this info is helpful.