Clematis montana

There's a week in late May when Clematis montana var. rubens comes into flower and the effect is so extravagant it borders on ridiculous. This is not a plant that does restraint. It covers walls, scrambles over outbuildings, swallows pergolas whole — and when it flowers, every inch of it is smothered in thousands of small, four-petalled, soft pink flowers. Thousands. The sheer volume is almost aggressive in its generosity.

The flowers are individually modest — about two inches across, a gentle shell-pink fading to blush at the edges, with a central boss of creamy-yellow stamens. But it's never about individual flowers with montana. It's about the mass effect, the cascade, the overwhelming abundance of pink tumbling over whatever structure you've given it. From a distance, a well-established montana in full bloom looks like a waterfall of blossom.

And then there's the scent. Vanilla. Warm, sweet, unmistakable vanilla, drifting across the garden on a May afternoon. Not all montanas are scented — 'Rubens' is one of the best for fragrance, and on a warm, still day you can smell it from the other side of the garden. I once walked past a cottage in the Cotswolds where a montana had colonised the entire front wall, and I stopped dead in the street because the scent hit me before I even looked up.

It grows fast. Alarmingly fast, in the right conditions — six metres or more once established. It needs something substantial to climb — a large wall, a mature tree, a solid pergola. Don't plant it on a flimsy trellis and expect a relationship built on mutual respect. Give it space, let it go, and once a year it'll thank you with the most spectacular display of any climber in the British spring.