The rosebay willowherb (Chamaenerion angustifolium) in the Arboretum is in flower and well worth a look.
This is a pioneer plant, among the first to colonise new ground. In America it is called fireweed because it is the first plant to take advantage of the space newly created by a forest fire. Fire sterilises the soil and breaks up its structure, turning it into an ideal seed bed for willow herb’s tiny wind-dispersed seeds.
Rosebay willow herb flowers form a spike called a raceme; each flower on the raceme will result in a long seed pod. In the header picture the fully formed pods are visible behind the flowers, and beneath each flower you can see the seed pods forming. Each pod will contain 300-400 seeds, a raceme will produce thousands of seeds, and a single plant can produce 60,000 seeds.
The pods dry when the seeds are fully formed and they open gradually, peeling back to expose the seeds. Not all the seeds blow away and the basket-like structure that the open seed pods form is a convenient landing place for foraging seed eaters.
Photographs by SMH