Sasha, a visitor who has a really good craft blog, has left a question: we have a cherry tree at the bottom of our patio. We didn't plant it, it grew from a seedling to a twenty foot tree in just six years!! Anyhow, in May this year all the lower leaves shrivelled up and dropped off!! Do you think it could be diseased?
Your cherry tree could be suffering from a couple of things, Sasha: the worst is a fungal disease called wilt, and there's nothing you can do about it except wait and see if it spreads and kills the whole tree. However, wilt usually occurs later in the year and another possibility is that the roots have been damaged. Cherry roots tend to be near the surface and often get caught by mower blades, or spades if you dig in the locality.
Another thing that struck me is that you said 'it is at the bottom of the patio' - does it have enough room for the roots to spread? If it is very confined, there is a chance that this is causing problems. If you think the roots are suffering, try a little t.l.c. : a two inch dressing of well-rotted compost in a radius of about five feet all round the tree, supplemented with a sprinkling of blood, fish and bone in spring.
Finally, very dry conditions (not likely last summer), or overly wet soil can be a problem. It's not in a boggy area is it?
I hope this helps. Please feel free to ask further about this or any other gardening questions.