The Smallest Garden

You don’t need a garden to be a gardener. You need a windowsill, a bit of light, and the willingness to take a box of soil as seriously as you’d take a border.

That’s the thing I love about window boxes. They’re the great leveller of gardening — as available to a third-floor flat as to a country plot — and yet they’re too often treated as an afterthought, a bit of colour stuck up to brighten the brickwork. Plant one properly and it becomes a real garden in miniature, changing through the seasons, feeding the odd passing bee, greeting you every time you look out. The smallest plot you’ll ever tend, and one of the most rewarding.

Here’s how I’d go about it.

Start with the planter, because it sets everything that follows. A long trough that sits the full width of the sill will always look better than something stranded and undersized. Beyond that it’s a question of taste and weight: fibreglass and plastic are light and modern and easy to lift; terracotta and metal are heavier and more traditional, and the weight matters more than you’d think once the thing is full of wet compost. If you’re handy, a length of timber from the DIY shop makes a fine box for very little.

One thing I won’t hurry past: if your sill isn’t wide and flat enough to hold the box securely, fix it to the wall with proper brackets before you plant a thing. A window box is heavier than it looks, heavier still after watering, and a box that works loose above a pavement is not a small problem. Do the boring bit first.

Before you choose a single plant, spend a day noticing the light. It’s the one piece of homework that decides whether everything thrives or sulks, and it costs you nothing but attention.

Watch the sill across the day. Does it bask in direct sun for six hours or more — the jackpot, for the widest choice of plants? Does it get a bit of morning or afternoon sun and shade the rest? Or is it in shade for most of the day? There’s no wrong answer, only different plants for each. Fighting the light you have is the surest way to a disappointing box.

Once you know your light, the choosing gets easy — and more fun. A few directions I keep coming back to.

For a sunny sill, you can be bold. Pelargoniums, petunias and fuchsias for colour that keeps coming; lavender or verbena if you want to feed the pollinators as well as please yourself. A shadier sill is no less rewarding, just a different palette: busy Lizzies flower their hearts out in shade, and coleus earns its place on leaf colour alone, no flowers required. (Ignore any list that files salvias under shade — they’re sun-lovers, and they’ll languish out of it.)

Then there are the approaches that work in any light, adjusted to suit. A single-plant box — nothing but nasturtiums, say, or a drift of lavender — has a calm, confident simplicity that a mixed box can’t match. A foliage box of ivy, euonymus and heather quietly carries the whole year, long after flowers have come and gone. And a herb box outside the kitchen window is the most useful thing you can grow — with one caveat: keep mint in a box of its own. Left in with others it bullies everything out within a season. Pair oregano and thyme, which both want the same sunny, sharp-drained conditions, and let mint thug away happily on its own.

The planting itself takes minutes. Out of their nursery pots, into peat-free compost, firmed in gently, topped up, and that’s most of it. No crocks or broken pot in the base, incidentally — the old drainage trick doesn’t work, and drainage holes are all a box actually needs.

Where a little thought pays off is the arrangement. The reliable trick is to think in three layers: something upright for height, something bushy to fill the middle, and something trailing to soften the front edge and spill over. Put the taller, showier plants through the centre, the trailing things at the ends or draped over the front, and leave each plant a little room to bulk out rather than cramming for instant effect. You can keep it neat and symmetrical or let it tumble — a looser, more rustic box has a charm the regimented sort misses.

A window box asks for one thing above all: water, and more of it than you expect. Containers dry out far faster than open ground — a hot sill in July can bake a box dry in a day — so this is the make-or-break. Check it often through summer, and water before the plants flag rather than after.

Beyond that, little and often. A weekly liquid feed keeps flowering plants going right through the season, since there’s only so much a box of compost can offer on its own. Pinch off flowers as they fade and the plants will keep making more, and the box will stay handsome for months rather than weeks.

None of it is difficult. That’s rather the point of a window box: a whole garden’s worth of pleasure, scaled down to something you can plant in an afternoon and tend from your kitchen sink. If you’ve been telling yourself you haven’t the space to garden, this is where you start. Right there on the sill.