I have a red-leaved acer [A. palmatum Dissectum Atropurpureum, I think the variety may be Garnet], which has lived in acid soil within a ceramic pot [about 40cm diameter by 30cm deep] in a sheltered shady spot in my courtyard garden for at least 10 years. The pot itself stands on the decorative shale top dressing of a raised bed, and is too heavy to lift, so I cannot really tell what the drainage is like. But it seems to have flourished well up to now without my doing more that watering it in dry spells and occasionally feeding it with Phostrogen in the spring and summer. After 10 years the acer is now about 90cm high by about 1.5m wide.
My problem is that it just seems to have stopped dead this spring. The bare branches [which are still flexible and green, not dead and brittle] produced the usual tiny red leaf buds at the ends in March/April, but these have not opened into leaves, in fact, nothing at all has happened since, and the whole plant seems to be in a state of suspended animation.
What have I done wrong, or not done? I have prised around in the soil, which does not appear to be either too wet or too dry. There was a period in March when we had a lot of rain and I noticed standing water around the top-dressing in the pot, so could it have "drowned" then? Or is it just too cramped in that pot [although it seemed fine last year]? Is there anything I can do to rescue it? I would be sorry to lose it, as it has a graceful arching shape and looks lovely normally. But it is right outside my kitchen window, and at the moment is a very sorry sight, and seems to be waving its branches reproachfully at me. Help please!!