Cosmos

Cosmos are the flower that taught me to stop trying so hard. I spent years fussing over temperamental plants and complicated colour schemes, and then I scattered a packet of Cosmos 'Purity' seeds along the back fence and watched the simplest, most beautiful thing happen.

By August, they were chest-height — slender, waving stems topped with the purest white flowers you've ever seen. Single petals, broad and clean, arranged around a golden-yellow centre. They look like someone drew the word 'flower' from memory. Nothing complicated. Nothing trying to impress. Just a flower being a flower.

They move constantly in the slightest breeze, which gives them this airy, dancing quality that makes the whole border feel alive. On a still evening in September, when the light goes golden and the first chill creeps in, a drift of white cosmos catching the last of the sun is one of the most beautiful things my garden does.

They're annuals, so you grow them fresh each year, but they self-seed generously. I've had volunteers popping up in the gravel path, between paving stones, in the compost heap. They have a talent for finding exactly the right spot.

As a cut flower, they're short-lived — two or three days — but so charming it doesn't matter. A handful in a glass with a few stems of dill or fennel from the herb garden, and you've got something that looks like it belongs in a Mary Wesley novel. They keep producing flowers until the first frost, which means months of free, effortless beauty.