Our wisteria is dying. Root rot?

August 24, 2019 3:23 AM

Our beloved 12 year old wisteria appears to be rapidly dying. Over the space of a week, all the leaves have started shrivelling. However, it has shown signs of being unwell for months. Best guess as to cause is root rot, I'd appreciate a second opinion. Also, how to plant a new wisteria in that location, if necessary, without it succumbing to the same thing.

Here are some photos. For years I've been aware that the vine had a curiously bulbous base, much wider than the main vine, with some parts of it appearing crumbly or hollow. Both the previous year's growing season and this one I was concerned by its lack of vigour, putting out surprisingly few new growth. And a couple of weeks ago we first started suspecting the leaves seemed dry-ish, not what you'd expect for mid-summer.

All the leaves on the plant have been shrivelling at the same rate, without any markings that suggest insect damage or mildew. It's not growing in a container, and the garden's soil is dry rather than damp.

First question: what is the likely cause? Second question: is it doomed? It sure seems that way, but if there's anything we could do to revive our beloved 12-year old green canopy, we'd try it.

Thirdly: If it dies, what do we do if we want to plant a new wisteria in that spot? If it is a fungus attacking the root, how do we protect the new plant?

posted by snarfois to Home & Garden (3 answers total)

In the US each state has a cooperative extension service which offers exactly this sort of (free) advice. You can send in samples and photos for experts to analyze. I don't see any exact equivalent in the UK after a superficial search but if you know of anything like this you are likely to get the best information there.
This page has some information that suggests it isn't likely to be root rot but maybe a graft failure? In that case there would not be a problem with replanting in the same spot. IANAPP (I a not a plant pathologist.)
posted by Botanizer at 7:30 AM on August 24, 2019 [2 favorites]

I can only answer your third question. My place had a mature wisteria die after budding early during a warm February a few years ago. We were super bummed out, removed the massive trunk which was all hollowed out, and just prepared to say goodbye. However the next year, it was sprouting vines again from what was left of the base and after a few years it's gotten long/tall enough so that we're guiding it back over the arbor again. That said, I know what killed our wisteria so it was a little easier to manage. In the climate I'm in, it's basically a weed.
posted by jessamyn at 9:39 AM on August 24, 2019 [2 favorites]

Bulbous base makes me think crown gall; definitely have a close look for weeping cankers or galls. I'm wondering if the white areas I see on the bulbous part are fungus? That could point to Armilleria. You'll have to replace the plant if you find them. If it's root rot you've got to make sure the next plant is not going to be in the same soggy conditions, either by making a raised bed for drainage or relocating the plant. If it's honey fungus/Armilleria, you probably need to find a vine that is not susceptible- not wisteria, in other words. The other issue may be that the graft has failed which can happen in plants up to 20 years old.

My personal feeling is crown gall due to the swollen base. This would be especially likely if your soil is alkaline. You will need to remove the wisteria including as much of the material underground as possible. Sterilize your tools after doing so. You'd then need to plant a resistant vine species. You local nursery should have some advice.
posted by oneirodynia at 8:17 PM on August 27, 2019 [1 favorite]