Facebook reminds you of your life in previous years and a brief view informs me that autumn is coming early this year. It’s possibly due to the fairly warm and dry summer. Maybe the plants have flowered and seeded earlier than normal and are now gathering their energy back in the roots. We have very little colour left in our front garden but fortunately the back is still looking good. Verbena Bonariensis is a perennial with tall stems topped by a lollipop of tiny purple flowers. They start to flower in the later summer and contrast well with other late flowerers like the bright yellow Rudbeckia, Black Eyed Susan.
You could buy one plant and in subsequent years have as many as you could possibly want. They self seed very well but are easy to identify and pull out if they become too prolific.