The tree dahlias this year are particularly spectacular. In previous years there's been intermittent flowering from late autumn to early spring but the weather has been unseasonably warm over the past two weeks and this seems to have encouraged the tree dahlias into mass flowering with bees going crazy for all the pollen which is covering the ground and plants beneath. Dahlia imperialis originates from Central America where the leaves were, apparently, used to supplement the diet in Guatemala. They're grown from the stalk which can be cut into sections (with 2 nodes) at the end of winter. The stalks can grow to 5 metres but are vulnerable to high winds so a sheltered aspect, such as next to a solid fence, shed or wall, is best.