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Hi Y'All

I have a wonderful Flapjack Plant which is overwintering in my cold conseratory.  It seems to be thriving, but the short thick stem seems to be covered with a white powder, just like talc.  Anyone got any ideas on this?  Can I brush it off with a soft brush or is it part of the plant's 'winter coat'.

I know the answer is out there - thanks in advance.

Regards