Verbena

If I could only recommend one plant to someone starting a garden from scratch, it might be Verbena bonariensis. It does something no other plant does quite as well — it creates this floating, transparent layer of tiny purple flowers on tall, wiry stems that you can see through, like a veil hung at waist height across the garden.

The effect is extraordinary. Because the stems are so thin and the flower heads so small, it doesn't block the view of whatever's behind it. Instead, it creates depth, layers, atmosphere. Plant it in front of something and it turns a flat border into a painting with a foreground.

It self-seeds with cheerful abandon, which means it turns up wherever it fancies — cracks in paving, the gravel path, that awkward gap between the shed and the fence. I let it. Half the joy of this plant is seeing where it decides to grow next.

Butterflies are absolutely mad for it. On a warm August afternoon, a patch of verbena can be covered in painted ladies and red admirals — it's like hosting a very well-attended, very beautiful party. The flowers keep coming from midsummer right through to the first frosts, which is a remarkably long season for something that asks for nothing but sunshine and the occasional bit of goodwill.