Hi!

I have a small orange 'tree', which I raised indoors from seed 4 years
ago. It has always grown extremely well, and I haven't experienced any
problems with it at all. Until now: all the leaves have dropped. I
haven't seen any bugs or strange coloring of the leaves before
dropping. What is remarkable, however, is that the leaves kind of
'break' exactly at the junction of the leave itself and the smaller
part that connects the leaf with the tree.

The tree also shows some vaguely brown, dried out, parts, starting
from the tops of some branches. However, I haven't changed my watering
habits ever, so I guess over- or underwatering is not the case. Just
recently (already after some severe leave-dropping), I moved the plant
to a new container with new soil (the same soil I've always used),
which gave me a chance to inspect the root system. It looked the same
as ever, healthy, quite dry actually, and still having space to grow
in the current container. I also cut off some of those brown branches,
hoping to stop this.

As spring is coming, the plant has developed quite a few fresh
branches (however still very small, only one or two inches long now)
with new leaves on it. But yesterday I noticed one of these new, fresh
leaves also dropping, exactly like the older ones have (a break on
this junction). The plant is standing before a sunny window, near the
heating (it has always stood there).

So, does anyone have a clue about what could be wrong here? I'd really
appreciate any suggestion, because after 4 years, the plant kind of
has become like a child to me!

Regards,
Mischa