I have an Acer palmatum dissectum also in an earthenware pot (~10"), and for
the last couple of years, in Spring it buds well and then gets a lovely
coverage of leaves, then about end of April/May time, half the leaves curl
up and fall off. The tree then lasts the season OK, but only with half its
leaves. The tree was bought already potted from the nursery and has bark
chippings on top to protect it. I've tried dressing the soil with iron
sulphate to try and acidify it a bit, so I'm hoping that will help, but it's
a strange thing to happen - if it were ailing, one would expect all the
leaves to fall off, and perhaps get branches dying back, but that isn't the
case here. Any ideas? I'm going to check for vine weavil, but I suspect
that it's clear as the pot is well protected.

Jason

Pot may be too small, but the cause is almost certainly a combination of too
much/bright sunlight for the tree to cope with (Acers like dappled shade) and a
lack of regular water. The reason for the top leaves being scorched and the
bottom/lower leaves being OK is because the top leaves are exposed to direct
sunlight. The lower leaves at least have the cover from the upper leaves, even
if they are dead.

Hope this helps,

Dave.