As I drove in to Sequoia this afternoon after four days at the Rotary District Conference, I immediately knew two things: that autumn had finally arrived in my absence, and that this week’s photo would be of the Tree Dahlia, or Dahlia imperialis. The imperial dahlia – how evocative a name! This herbaceous perennial grows from the ground each year, then carries its flowers on huge stems, more like reeds, that can be over 6 meters (20 foot) high! What is more, no flower is so perfect for looking at from below, its delicate mauve petals backlit and seen against blue sky or green – or better still, butter yellow (autumn) – foliage. And I’ve not cheated. The second pic is merely a detail from the first. Without a doubt, no flower represents the last weeks before the frost more perfectly or dramatically than the large cups of the tree dahlia.