Why herbs thrive on a sunny windowsill

Most of the herbs we reach for in the kitchen are Mediterranean plants at heart. They want sun, sharp drainage and air moving around their leaves. A windowsill that gets four to six hours of direct light a day — ideally south or south-west facing — gives you exactly that, plus the warmth they crave in a British summer. A kitchen sill is convenient, but check it before you commit: a spot right above a radiator will cook roots in a small pot, and single-glazed windows can be surprisingly cold at night in April and May. Turn your pots a quarter-turn every few days so stems grow straight rather than leaning into the glass.

Windowsill growing is really container growing in miniature, which means the rules of watering and feeding matter more, not less. A small volume of compost dries out quickly and its nutrients are used up within a few weeks. Get those two things right and you will be cutting your own basil from June to October.

Choose pots and compost that suit small roots

Herbs dislike sitting in soggy compost far more than they dislike drying out briefly. Drainage is therefore the first consideration, not the last.

• Size: a 15–20cm pot is plenty for basil, parsley or chives. Mint is a thug and will appreciate 24cm or a 3–5 litre pot.
• Drainage holes: essential. One hole in the base is the bare minimum; three or four is better.
• Material: terracotta looks lovely and breathes, but dries out roughly twice as fast as glazed ceramic or plastic. In a hot, bright window, plastic may actually be kinder.
• Compost: a peat-free multipurpose with added grit or perlite, or a dedicated herb compost. Fill to about 2cm below the rim so you can water without it spilling over the edge.
• Saucers: useful, but empty them after twenty minutes. Standing water leads to root rot and fungus gnats.

Four reliable herbs for a modest sill

If space is tight, these four earn their place. Buy small plants rather than sowing seed late, and you can be harvesting within a fortnight.

• Basil: thirsty, hungry and hates the cold. Keep it warm, water little and often, and pinch out flower buds the moment they appear — once it flowers, the leaf flavour turns harsh and peppery. Supermarket pots are crammed with seedlings; split them into two or three pots and they will double in size.
• Mint: the opposite temperament. It likes moist compost and will tolerate a little shade. Always grow it in its own pot, as it spreads by underground runners and will swamp its neighbours.
• Parsley: a biennial, so treat it as a one-season crop and sow or buy fresh each spring. Flat-leaved types have the better flavour; curly types are hardier in a cold snap. It resents drying out and resents being moved.
• Chives: the toughest of the four, happy in a slightly smaller pot and the first to regrow after cutting. The purple flowers are edible and excellent scattered over a salad.

Watering: the skill that decides success

Check your pots daily in July and August, and every two or three days in spring and autumn. Push a finger 2cm into the compost: if it feels dry at that depth, water. If it feels damp, walk away.

Water in the morning where you can, aiming at the compost rather than the leaves; wet foliage overnight invites mildew, especially on mint. Pour until a little runs out of the drainage holes, then stop. A common mistake is the daily splash — a small, shallow drink that wets only the surface and encourages weak, shallow roots. The opposite error, leaving pots standing in a saucer of water, kills more windowsill herbs than anything else. Basil will droop dramatically when thirsty and usually revives within an hour of a good soak; if it stays limp, the roots have rotted and it is time to start again.

Feeding lightly, not lavishly

Fresh compost feeds a plant for roughly four to six weeks. After that, a weekly feed keeps leaves coming. Use a liquid feed at half the strength recommended on the bottle, and apply it to damp compost rather than dry, which avoids scorching the roots.

• Basil and parsley are the hungry ones — feed weekly from June to September.
• Mint and chives need far less; a fortnightly half-strength feed is plenty.
• If you would rather garden organically, a liquid seaweed or comfrey feed works well.
• Stop feeding by early October, when growth slows and unused nutrients sit in the compost.

Harvest often and they will keep producing

Regular picking is not greed, it is pruning. Every cut tip encourages branching, and branching means more leaves. Never strip a plant bare.

• Basil: pinch the growing tip just above a pair of leaves, always leaving at least two sets below. Remove flower buds promptly.
• Parsley: take the outer stems at the base, working inwards, and leave the tight centre to keep growing.
• Chives: snip whole leaves about 2cm from the compost. Never trim the tips only, which leaves the plant looking tatty and slows regrowth.
• Mint: cut stems back by a third, and use the top leaves first — they are the most tender.

Rotate your pots a little, keep the leaves dry, and you will have fresh herbs within arm's reach of the kettle from late spring until the light fades.