Trees and shrubs frequently asked questions

A question submitted by Margaret O'Dell via our Ask a Question page:

“My Rhus typhina is about 5 years old. Up until now it has been beautiful but this year it looks as if it's dying. Leaves shrivelled up before they came out and the suckers are coming up everywhere. HELP please... what should I do? Thanks, Margaret O'Dell”

Chris replies:

Okay, we suspect this is a problem called Verticillium wilt and your photos show it graphically. Basically, the soil-borne fungal disease affects the roots so interfering with the plumbing (water uptake from the roots) of the plant causing dieback on the stems and for the leaves to wilt. It’s common on Rhus trees as well as lots of popular garden plants. I suspect what has made it more dramatic is Rhus are shallow rooted large shrubs / small trees so the effect is more dramatic. However, the self-preservation aspect of Rhus is now coming into play with the suckers developing quickly as the main tree fails. We would recommend cutting the tree back by half to see if it can be saved. However, if nothing shows by the autumn, remove the tree but elect one of the suckers to become the new tree and cut down the remaining suckers so all the energy goes into the one plant. Hopefully this new plant will develop and the roots will not be unaffected.


Alas there is no chemical control for this disease, however I’m sure the determination of your Rhus will mean a stronger replacement tree develops quickly. Do bear in mind, however, if the wilt has affected all the soil then it could strike again at anytime. If this seems likely, then remove as much of the Rhus root from the area and plant a tree which is known to be resistant to the disease.


The Royal Horticultural Society produces a list of resistant plants: Alnus (alder), Gleditsia (honey locust), Betula (birch), Ilex (holly), Carpinus (hornbeam), Liquidamber (sweet gum), Cercidiphyllum (katsura), Morus (mulberry), Crataegus (hawthorn), Platanus (plane), Eucalyptus (gum tree), Populus (poplar), Fagus (beech), Salix (willow), Ginkgo (maidenhair tree), Zelkova. Conifers are immune to the disease.


We hope this information helps.

To check to see if your plants are susceptible to Verticillium Wilt, please check this useful link: http://www.rhs.org.uk/Media/PDFs/Advice/Verticillium-host-list-NEW