I have included hairy St John's wort (Hypericum hirsutum) in my series on woodland flowers but, in truth, it could have been included elsewhere as in addition to open woodland rides and woodland edges it occurs on river banks, in ditches and along hedgerows. It has a preference for lime-based soils and so, in Dorset, my perception is that it is most likely to be found in woodland on the chalk.
At first one might mistake it for yellow loosestrife; it is a tall plant with spikes of large, pale yellow flowers. On closer inspection, however, it can be seen to be quite different in many ways and that it bears the hallmarks of the Hypericum family; opposite, rounded leaves and five pointed petals with pronounced stamens. Yellow loosestrife likes damper conditions too.
This plant is the only St John's wort or Hypericum to have a downy covering of hairs on the stems and leaves, hence its name, hirsutum means hairy.