Gardening Q&A: what can we do about a damaging Robinia Frisia tree?

The roots of a Robinia tree have damaged parts of my driveway. What can we do about it?
Question: I would be most grateful for your views on a Robinia pseudoacacia tree which stands literally one metre (39 inches) away from the edge of our garage wall. It was planted by previous neighbours 10 years ago and has since grown to a height of 50 feet. 

The roots over the past 18 months have damaged parts of my driveway and they appear now to be approaching a drain situated 1.6 metres away from the main trunk of the Robinia. One of the tree branches had in the past broken off and caused damage to some roof tiles of the garage.
 
My present neighbours and I both are keen to remove the tree rather than prune the branches. We have learnt that such trees should never be planted near a house or a water drain and that the seeds which are plentiful are toxic if ingested by animals or small children.
 
What is your experience with Robinia “Frisia” and how do you feel we should proceed?

Answer: Robinias do have a reputation which they are not shy to live up to. Branches tend to be brittle, dropping in high winds. After pruning, they tend to become more prone to breaking when awkward angles are created by vigorous upright regrowth. Large pruning cuts can also make the tree susceptible to rotting diseases. 

At the very least the tree should be the same distance away from the house as the ultimate height of the tree. So all in all, the future does not look bright for the robinia, especially in view of its track record to date.

Your main problem will be eradicating suckers which arise from various points along roots. Treat the stump at the time of cutting with a stump killer such glyphosate-based product RoundUp Tree Stump and Root Killer. With the tree shocked at being cut down, these suckers may continue to appear for a couple of years, so you may need to persist with applying glyphosate to the suckers.

Send your questions for the RHS to: gardenproblems@standard.co.uk.

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