Why a kitchen windowsill earns its keep

Fresh herbs are the difference between a decent dinner and a very good one, and the shortest route from plant to pan is the sill above your sink. A few snips of basil for a tomato salad, or a handful of chives for scrambled eggs, without a trip to the shops. You also notice problems early, because you look at the plants every day.

The catch is that a windowsill is a peculiar little microclimate: bright but often draughty, warm by day and chilly by night, and drier than it feels. Work with those conditions rather than against them, and three or four pots will crop for months.

Pick compact, reliable herbs

Not every herb suits indoor life. Rosemary, thyme and sage want far more light and much sharper drainage than a kitchen sill usually offers; they sulk, go leggy and attract mildew. Stick to leafy, soft-stemmed types that cope with regular cutting.

• Basil — the classic. Choose a compact bush type rather than a large-leaved Italian variety that will bolt skywards. Supermarket pots contain dozens of seedlings crammed together; split them into two or three pots within a day or two of buying, or they will smother one another.
• Parsley — flat-leaved for flavour, curly for looks. It is a biennial, so a plant crops hard for a year then runs to seed. Sow seed in late summer for winter picking, or buy a healthy pot and divide it.
• Chives — the most forgiving of the three. A clump regrows after every cutting, tolerates a north-facing sill far better than basil, and can be lifted from the garden or allotment in early spring, split with a knife and potted up.

Add mint only if you are prepared to keep it in its own pot, because it runs. Corsican mint stays small, but ordinary spearmint will fill a trough in a season.

Pots, compost and drainage

Use pots at least 12–15cm across for a single basil plant, and something wider and shallower, around 20cm, for a chive clump or parsley. Terracotta looks lovely and breathes well, but it dries out fast on a warm sill; plastic or glazed ceramic holds moisture longer. Whatever you choose, drainage holes are non-negotiable, and a saucer underneath protects the paintwork.

A peat-free multipurpose compost is fine, but lighten it with about a quarter by volume of horticultural grit or perlite. Herbs hate sitting in soggy, airless compost, and the extra grit makes overwatering far less punishing. Fill pots to about 2cm below the rim so you can water properly without it running straight off. If you are reusing pots, scrub them and rinse well — old compost harbours fungus gnat larvae and damping-off spores.

Light is the limiting factor

Basil wants six hours of good light a day, ideally more. A south- or west-facing sill from March to September is perfect, but by October the light drops off so sharply that even a sunny window struggles. Expect to sow or buy fresh plants in spring rather than coaxing one through a British winter. Parsley and chives are more tolerant and will tick over on an east-facing sill.

Rotate pots a quarter turn every few days so stems grow straight rather than leaning into the glass. In deep winter, move plants to the brightest window you have and accept slower growth. If plants stretch, with long pale gaps between leaves, the light is too low: pinch the tips back and start again in spring.

Watering, feeding and the winter problem

Little and often beats a weekly flood. Check the compost by pushing a finger in to the first knuckle: water when it feels dry at that depth, and let the pot drain freely. Standing water in a saucer is the quickest way to kill herbs, so empty it after half an hour. Watering from below, by filling the saucer and letting the compost draw it up, keeps the leaves dry and reduces mould.

Feed lightly. A weak liquid seaweed or tomato feed every fortnight through spring and summer is plenty; too much food makes soft, tasteless leaves. Stop feeding from November to February.

• Keep pots away from radiators and open windows — hot dry air and cold draughts both cause leaf drop.
• Watch for fungus gnats hovering over compost: they signal consistently wet soil. Let the surface dry out between waterings.
• Greenfly love indoor basil. Squash them by hand or wash the leaves under a lukewarm tap rather than reaching for sprays you would rather not use on food.

Harvesting for a long, steady supply

Regular cutting keeps herbs bushy. With basil, pinch out the growing tip just above a pair of leaves — two new shoots will break from that point. Work from the top down and remove any flower buds the moment you see them; once basil flowers, the leaves turn bitter and the plant gives up. Never strip more than a third of a plant at once.

Cut parsley stems from the outside of the clump, taking whole stalks at the base rather than just the leaves, and the centre will keep producing. Snip chives about 2–3cm above compost level with scissors and they will regrow within a fortnight; leave a few unopened flower buds if you want the pretty purple heads for a salad.

Finally, give tired plants a holiday. In June, move windowsill pots outside to a sheltered, semi-shaded spot, or repot them into fresh compost, and they will often reward you with a second flush well into autumn.