plant with translucent stem

 


I have just seen a plant in an "Open Garden"that I would like in my
garden but
the owner does not know its name. It has a singlebtranslucent
stem (a bit like a
balsam plant  but it is a perrenial,not an annual)
and has pale greeny- grey
leaves with a serrated edge. It is about 6
feet tall and in a pot.She says it
has survived the winter but that she
put it in her conservatory during the
recent freezing spell. Can anyone
tell me what it is. please?




--
Patricia
Thorpe