Why doesn’t my tree dahlia flower?
Vic Styles, Southampton
Stefan says: Two years ago, you bought tubers of the tree dahlia variety ‘Pink Flash’, which has grown to over 1.8m tall in a pot and produced magnificent foliage, but with none of the hoped-for pink flowers. You wonder what you can do now.
I have to say I don’t find the tree dahlia, Dahlia imperialis, an easy plant to grow because, although it’ll do as yours has done and produce wonderful leaves, it’s fussy about the growing position if it’s to flower. I don’t think it will do so as readily in a pot because it needs a sunny, warm, very sheltered position in a rich, moist soil.
The warmth and shelter are important as the stems are easily damaged by wind. It’s also not fully hardy and the tubers should be lifted now and stored over winter for replanting in spring.