Why the kitchen windowsill earns its keep

A sunny kitchen windowsill is the most productive square metre in most British homes. It sits close to the kettle, catches whatever daylight the weather allows, and keeps herbs within arm's reach of the chopping board — which, in practice, is the difference between a plant that gets used and one that quietly dries out behind the microwave.

The catch is that a windowsill is a peculiar growing environment. It can be blazing hot in July and chilly in January, the light is one-sided, and the radiator below it will dry out compost faster than almost anywhere else in the house. Choose the right herbs, though, and you can be cutting fresh leaves in the depths of a grey February.

The hardiest herbs to start with

If you are new to growing on a sill, begin with plants that tolerate a bit of neglect and cope with lower light levels. These are the ones that will still be alive in March.

• Chives — almost indestructible in a pot. Snip the leaves to about 2cm from the base and they regrow within a fortnight. The purple flowers are edible and lovely scattered over salads.
• Mint — grow it in its own pot, always, because it spreads aggressively. Keep it watered and it will supply you with leaves for mojitos and new potatoes all year. Spearmint is the best all-rounder for cooking.
• Flat-leaf parsley — slow to germinate from seed, so buy a plant. It copes with a north-facing sill better than most and a single healthy plant will keep cropping for months.
• Thyme — a Mediterranean herb that resents soggy roots. Terracotta, gritty compost and a sunny spot suit it perfectly. Winter thyme is far more pungent than the supermarket bunches.
• Rosemary — a woody shrub rather than a soft herb, so give it a slightly larger pot. It hates being waterlogged and will sulk if the saucer is left full.
• Winter savory and oregano — both compact, both tolerant, both excellent with roast vegetables and chicken.

Tender herbs that are worth the effort

Some herbs are simply not going to survive a British winter on a windowsill, but they are so useful that it is worth treating them as seasonal crops and replacing them.

• Basil — the classic windowsill herb, but only if the sill is genuinely sunny and warm. Water from below, pinch out the growing tips regularly, and never let it sit in cold, sodden compost. Sweet Genovese is the standard; Greek bush basil is neater for small sills.
• Coriander — bolts quickly in heat. Sow seed little and often, in succession, rather than trying to keep one plant going for months. Slow-bolt varieties give you a longer window.
• Dill — feathery, fast and fussy about being moved. Sow it directly into its final pot and keep it out of direct midday sun.

Buying a supermarket pot of basil or coriander is fine as a starting point, but the plants are grown densely and forced. Split the clump into two or three pots, remove the weakest seedlings, and give them a fortnight to settle.

Matching herbs to your light

Before you buy anything, work out which way your window faces.

• South or west facing — the warmest, brightest option. Basil, coriander, dill, thyme, rosemary and sage all thrive here. Watch for scorching in high summer; move pots back from the glass or shade them with a sheet of kitchen paper.
• East facing — gentle morning sun, which suits parsley, chives, mint and chervil beautifully.
• North facing — the toughest spot, but not hopeless. Stick to mint, parsley, chives, chervil and rocket. Keep the glass clean so every bit of light counts, and rotate the pots weekly so they do not lean permanently towards the window.

Pots, compost and daily care

Size matters more than style. A plant in a cramped pot dries out within a day in summer and runs out of nutrients within weeks. As a rule, give a supermarket herb a pot around 15cm across, and a shrubby herb like rosemary 20cm or more.

Use a peat-free multipurpose compost mixed with about a quarter grit or perlite for Mediterranean herbs. Every pot needs a drainage hole, and a saucer underneath protects your sill. Water in the morning where you can, aiming for the compost rather than the leaves, and water from below when the surface feels dry to the touch. Empty the saucer half an hour later — standing water is the fastest way to kill thyme and rosemary.

Feed every two to three weeks from March to September with a general liquid fertiliser. Rosemary and thyme prefer a weaker dose than basil and parsley.

Harvesting and keeping them going

The secret to a productive windowsill is regular snipping. Left alone, most herbs will run to flower and stop producing leaves; cut them, and they branch and bush out instead.

Always pinch or snip just above a pair of leaves, never into bare stem. Take no more than a third of the plant at once. With basil, pinch out the top pair of leaves every week or so; with chives, cut the whole clump back to 2cm occasionally and let it regrow.

Watch for the two classic windowsill problems. Yellowing lower leaves usually mean overwatering — let the compost dry a little and check drainage. Pale, spindly, leaning growth means too little light: move the pot, or accept that the sill will not support that particular herb and swap to a tougher one. A weekly check for greenfly under the leaves, and a wipe with a damp cloth for dust, will keep everything in good order.

With a handful of hardy perennials, a rotating crop of basil and coriander, and a little attention each morning, your windowsill will quietly out-produce any supermarket herb shelf — and smell considerably better while doing it.