Answer: Wisteria vines are very large and heavy plants, over time they develop thick trunks at the base; unfortunately gardeners often underestimate the mature size when deciding where to plant it, and over the coming decades may neglect the routine pruning required to keep it within bounds. Each of these wisteria vines will have stems up to 25 feet long at maturity -- so just one could more than cover your pergola easily. The support must be proportionately strong and able to withstand the weight of the vine, the vines become extremely heavy especially when wet and act like a sail in a wind storm as well. In my experience a brick or stone pillar, for instance, or a thick iron post is a good support for the long term. If you are concerned it might overgrow your pergola, and this is a valid concern, then you could train the vine into a freestanding tree form planted in the center of a lawn area. This also prevents it from spreading excessively from the roots since you are constantly mowing the surrounding area. The following web site offers detailed information on how to plant, train, and prune a wisteria including instructions for growing it in tree form.
Enjoy your wisteria vines!
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