Or you could plant something else that's slower growing but longer lived. RE: Mountain Ash tree seems to be dying - why? Sorry to hear your tree is not doing well. If you were (much) closer I would give you one of our seedlings. I have two or three (volunteers) growing in the yard that will have to go soon. BP: Good info as usual. I am probably one of the lucky ones for this particular tree as my soil is acidic and well drained. Here is hoping I get another 50 - 60 years (and I am around to see it;-) from mine as it is less than a decade old. RE: Mountain Ash tree seems to be dying - why? Sorry to hear about your tree. It's like losing a friend when a tree dies like that. Mountain Ash trees are susceptible to a fungal disease called fireblight. I have seen healthy trees suddenly die as you described. There doesn't seem to be a cure, but sometimes if only a few branches are affected you can prune them out and the tree can then survive for a long time. You have to cut back to healthy stock, and make sure to disinfect your tools. If you are able I would get an arborist to give you a diagnosis. Good Luck.