I think it was Kerri who asked if the Tree Dahlias (earlier post) were a tree or a shrub?
They are neither. They are simply a very much larger version of a regular dahlia. They usually grow to a height of about 3 metres (10 ft) on thick, segmented stems from tubers.
They can propogated from tuber division. or the stems can be cut into sections - include at least two 'joints' in each section - and plant them horizontally in the ground.
We find the lower leaves tend to die off before flowering but these are easily removed to keep the plants looking neat and tidy. The stems are so strong that they don't require staking - what a bonus !!