Dieback on leaves.

I have this Pachypodium but the leaves keep turning black from the tip downwards, and then shrivel up completely.
As a result it has very few leaves.
It has had this condition for a long time and I have repotted it and moved it to several different positions, but it has not cured the leaf problem.
Please does anyone know what causes it and how can I put it right.
Thank you ...

 

Not sure about the leaves turning black, but they are deciduous, and they like warm conditions.
If you dry them out all of the leaves can drop.
I grew one on for a few years until it got too big and I moved it to my frost free greenhouse, it didn't survive.

 

Thank you @pete I my have kept it too dry. I'll give it more water.

 

I wouldn't water it too much now, unless its in the house and 20c plus.

 

Thanks. It's in the kitchen. I'll bring it into the living room where it's warmer.

 

It's a lovely plant

Do they originate from Madagascar?

 

Seem to remember they do @Zigs.
As such basically tropical, mine used to drop all its leaves every winter, then regrow more on the new growth in spring, a bit like many of the Euphorbia succulents do.

 

Thought it looked pretty Lemur proof

 

That's a beautiful plant @pete How tall is it ?
Mine used to have a full head of leaves like that but now they keep turning black and dying. That's what I can't understand.

 

That pic was taken in 2007 Michael, the plant is long gone, died the first winter I moved it to my frost free greenhouse.
Cant remember how tall it was, but it did branch out quite well.

I'd not worry too much about leaf loss, the leaves, although nice to look at, are only borne on new growth and tend to fall during dry spells when the plant is not in active growth.
Which in this country has to be winter.

 

Thanks @pete I feel better about it now