We were gifted a wisteria from my husband’s grandmother’s well established wisteria. We would like to plant it in the back corner of our yard and build a pergola with benches around it to provide a sturdy structure for it to climb. I have been planning on planting the wisteria in an open bottomed planter in the corner of the pergola so that the roots of the wisteria have full access to the ground underneath the planter. I was planning on having built in benches attached to the side of the planter. I was planning on building the planter 18″ x18″. Is this plan reasonable? Does the planter need to be bigger? I was a little concerned as a previous answer mentioned freezing as a problem with using planters but we were planning on having the bottom open to the ground.
I understand your concern about the issue of over-wintering plants in planters/container. See, for example, a previous post on our Ask a Master Gardener website, Wisteria. This might be the one to which you were referring.
From your description, I have a feeling that, to match the benches, your planter would be made of wood – this would not retain moisture or moderate soil temperature, so the plant roots would be at high risk of root rot, as noted in the earlier post. If you wish to grow the wisteria in a container, I’d suggest that you use a more conventional planter/pot. From the information you provide, I’m not certain of the size of your plant. It’s generally recommended to use a container that is 3-4 times the size of the root ball, and to repot the vine as it outgrows the pot. The container size you suggest – 45 cm (18 inches) – would suffice for a larger plant.
An alternative might be to simply plant the root ball of your wisteria in the ground, on the spot where you intended to place the planter/benches. Ideally, this spot should get full sun, so the wisteria blooms happily. Let the vine grow for a couple of years, to make sure it’s doing well and does not have to be moved. Then add the benches, with the matching bottomless “planter” around the vine. The “planter” would act more like a 4-sided cage around the plant, not as a container. The presence of the hollow “planter” structure would encourage the plant’s twining growth to be directed to the pergola. And this would look lovely, highlighting the beauty of the wisteria.
All the best with the precious wisteria – there’s so much family history intertwined with it!
August 29 2021