Accidents will happen: Let nature take over in your garden

They're annoying, people who claim they just "threw" something together. My neighbour can do it. She strolled down the street this morning towing two kids to nursery, wearing a voluminous green knitted woollen thing that I'd have been scared to buy, paired with an assymetric pair of grey suede high heels. Needless to say, she looked amazing. "Oh, I just chucked it on," she claims.

For those of us who require hours of planning to produce any semblance of sartorial normality, this is a big lesson in life's general unfairness. How did the clothes-throwers end up with this magical skill?

But happy accidents can occur outside of fashion, too, thank goodness. Horticulturally, a good accident is sort of what I'm hoping for most years. Planning in gardening is fine – it is certainly possible to co-ordinate colours in spring when not much is growing yet. (You can choose all black tulips and deep-violet hyacinths and for a moment your plot will exhibit something close to a controlled effect.)

Yet the year presses on, and nature takes over. You'd have to be a control freak of Dutch proportions to resist (and I say that advisedly, having visited a series of Netherlandish gardens over the years, all of which were tidier than any British garden I've ever been into). You can force the overall structure, yes, by trimming shrubs and clipping out branches. But gardening in the end is trial, error and genuine accident.

This is down to a number of factors. For a start, you can't even check your materials before you start. It's less throwing on clothes in the half-light of dawn and more doing it completely in the dark. You never really know what you have till it's flowering. Modern colour-printing might be great, but it can't show you a petal with the sun shining through it on a late summer afternoon, its colour utterly changed and illuminated. That cunning combination of orange and purple you carefully planned? Hideous. That weird little plant you thought was going to look terrible in with the roses? Magical.

Second, your garden won't sit still. You buy a plant imagining it's about the size it'll be next year. It puts on 3ft of growth the first summer. Or it doesn't, when you were rather hoping it would. Either way, it's not that easy to plan.

But there's a deeper level of accident, too. There's the times someone gives you a plant you weren't expecting: this April, I gave away a load of jars on Freecycle to a woman who was making jam, and she brought me back Marmande tomato seedlings as a thank you. Or the times they introduce themselves: two years ago, a 10ft Echium pininana (above) seeded itself from my garden into my neighbour's, much to her delight.

If you find all this frustrating, you have only a few options: cactuses grow so slowly they're practically stationary; or you could go Dutch, with highly clipped hedges, bulbs and vegetables in rows.

Me, I'm off to enjoy the lilac slice of cyclamen across the end of my garden that appeared from nowhere.

Chance encounters

Victoria Summerley

Gardening blogger at victoriasbackyard.blogspot.co.uk

"A euphorbia characias which seeded itself in my garden. It converted me into a fan; it looks fabulous in spring, with lime-green flowers that last."

Mark Diacono

Author of 'Fruit – River Cottage Handbook', otterfarm.co.uk

"Little nasturtiums, which climbed into a Szechuan pepper and around its trunk, and flowered next to the peppercorns."

Laetitia Maklouf

Author of 'Sweet Peas for Summer'

The summer after I planted my garden I neglected to mow and dandelions came up. They were like sparkling puddles of sunshine and made me pro-yellow.