Coreopsis

Coreopsis 'Moonbeam' is one of those plants that does something very simple, very well, for a very long time. It flowers. Small, soft-yellow, daisy-like flowers, about an inch across, with a slightly deeper yellow centre. Nothing complicated, nothing dramatic, nothing that would make a plantsman raise an eyebrow. Just an endless succession of cheerful, pale-lemon daisies from June until October — five solid months of gentle, undemanding colour.

The foliage is fine and feathery — thread-like leaves so delicate they create an airy, hazy texture in the border, almost like a green mist beneath the flowers. It's this combination of soft flowers and fine foliage that gives 'Moonbeam' its distinctive quality — it looks light, weightless, as if it might float away. In a border full of heavy, structural plants, 'Moonbeam' is the palate cleanser. The space between the bold gestures.

It grows about eighteen inches tall and spreads steadily by underground runners, forming a broad, dense clump that suppresses weeds and fills gaps with quiet efficiency. I planted three in a sunny border five years ago and they've merged into a single, continuous drift that hums with hoverflies all summer. The dead flowers drop cleanly, so there's almost no deadheading required — it just keeps going, a self-maintaining machine of soft yellow.

This is a budget-friendly plant by anyone's standards. Garden centres sell it for a few pounds. It needs no staking, minimal watering, no feeding, and only occasional division every three or four years when the centre starts to thin. The Perennial Plant Association in America named it Plant of the Year in 1992, which tells you everything about its reliability. It's not the most exciting plant in the border. It's not supposed to be. It's the one that makes everything else look better.