I WAS recently asked by a friend for some advice centred around a tree they inherited when they moved into their new home.

It’s a 30-year-old mountain ash (Sorbus), which has limped along for the last two years and has some large cracks/mini fissures in its bark.

I’m not able to see the tree in person as it’s the other end of the country but I’m convinced that the likelihood of bad news is likely to be on the horizon.

Splitting bark on any tree or shrub should set alarm bells ringing and should never be overlooked.

It is possible for trunks to split due to freezing where damage may have occurred in the past, creating cavities or spaces where water can enter and then freeze. This, however, is not normally the reason for it happening - underlying disease is normally to blame.

We have some ancient crab apples close to the nursery that are in terminal decline and one or two have some enormous cracks and splits in their main stems caused by fungal decay.

I suspect that in the case of my friend's Sorbus disease will have been present for some years before anyone was even aware of it.

I can’t name the specific disease without seeing the tree in person but my money would be on a fungal disease that for whatever reason has taken hold.

Normally this happens when a tree is under stress, due perhaps to compaction around the roots or excessive waterlogging.

The stage at which the fungus causes the bark to split is almost the ‘final act’ when there is nothing you can do to remedy the problem.

The bark of a tree is its skin. It protects the living tissue just beneath and once that is breached there is no way of covering it back up.

The best course of action would probably be to remove and replant with a different tree altogether in a fresh location and choose a tree with good natural resistance to fungal disease.

Next topic

Using a cloche in the garden


Clean pots, seed trays and greenhouses ready for use in the spring. Either use hot soapy water or horticultural disinfectant.

Plan your vegetable crop rotations for the new season ahead, setting out designated areas to grow specific crops

You can start forcing rhubarb by placing a traditional forcer or plastic/metal bin over established plants

Dig over any vacant vegetable plots that have not yet been done and add some well-rotted manure