A windowsill is a proper growing space

Anyone who has paid a couple of pounds for a wilting supermarket basil knows the frustration. It looks generous on the day you buy it and is a bare stick by Friday. Growing your own on the kitchen sill costs very little more and gives you a steady supply of leaves for most of the year. A south- or west-facing kitchen window catches useful light in the UK from late February onwards, and because you are in and out of the kitchen anyway, you will actually notice when a plant needs attention — which is half the battle.

The trick is to treat each pot as a miniature garden rather than an ornament. Windowsill herbs fail for three predictable reasons: soggy compost, not enough light, and never being cut. Get those right and the same plants will crop for months on end.

Four herbs worth your windowsill

You can grow almost anything in a pot, but these four earn their space. Keep them in separate containers — mint is thuggish and will smother basil if they share.

• Basil — the thirstiest for light and warmth. Give it the brightest spot you have and keep it away from cold glass in winter, where it sulks and blackens.
• Mint — the most forgiving. Ordinary spearmint or Moroccan mint will grow almost anywhere, including a north-facing sill, though it will be slower and leafier.
• Parsley — flat-leaved types have better flavour than curly. It is a biennial, so sow fresh each year rather than coaxing an old plant through a second season.
• Chives — the toughest of the four and happy to be snipped hard. A 15cm pot will give you clumps for years if you divide it each spring.

Compost, pots and drainage

Free-draining is the watchword. Use a peat-free multipurpose compost with roughly a quarter extra perlite or horticultural grit mixed through. That feels like overkill, but it is the difference between roots that breathe and roots that rot in a plastic pot sitting on a sill where the air barely moves.

Allow a 12–15cm pot per plant, or a 30cm trough for three. Terracotta looks lovely and dries out faster; plastic holds moisture longer but needs more grit to compensate. Always choose pots with drainage holes and stand them on a saucer or a deep tray — you will need that tray for watering from below anyway.

Never fill pots with soil straight from the border. It compacts in a container, harbours vine weevil, and brings weed seed with it. Fresh compost every time, and wash old pots before reusing them.

Water from below, and water properly

This single habit changes everything. Pouring water onto the surface washes nutrients out of the compost, splashes the foliage — which encourages grey mould and mildew in still air — and usually leaves the middle of the rootball bone dry while the base sits waterlogged.

Instead, fill the saucer with 2–3cm of water and let the pot drink for twenty minutes. Tip away whatever is left. Moisture wicks upward, the surface stays drier, and fungus gnats and damping-off have far less to work with.

Frequency matters more than volume. In summer, most windowsill herbs want a drink every two or three days; in winter, once a week may be plenty, and basil on a cold sill often needs almost none. Push a finger 2cm into the compost — if it feels damp, wait. Water in the morning where you can, and let tap water stand for an hour so it is not icy cold.

Light, pinching and feeding

Aim for six hours of decent light a day. South-facing is ideal, east is workable, and a north-facing sill will manage mint and chives but will leave basil pale and drawn. Turn pots a quarter-turn every few days so stems grow straight rather than leaning into the glass. In December and January, expect growth to slow and cut back on watering rather than reaching for a lamp.

Pinching is where most gardeners are far too timid.

• Basil — pinch out the growing tip just above the second or third pair of leaves once the plant has about six leaves. Repeat every fortnight. Never strip a stem bare; always leave two sets of leaves behind.
• Mint — cut whole stems back to 5cm from the compost. It regrows fast and the top leaves are the tender ones.
• Parsley — harvest outer stems right at the base rather than the crown, so the centre keeps producing.
• Chives — snip 2cm above the compost with scissors, taking tufts rather than single blades. Remove the purple flower buds unless you want them in a salad.

Feed lightly. A half-strength liquid feed every fortnight from March to September suits basil, parsley and chives; mint rarely needs any. Overfeeding gives soft, flavourless growth.

When things go wrong

Yellow lower leaves and a sour smell mean waterlogged compost. Stop watering, move the pot somewhere airy, and check that the drainage holes are not pressed tight against a saucer.

Leggy, pale basil with small leaves is short of light. Move it to the brightest sill you have and pinch it back hard — it will branch from below the cut.

Tiny black flies hovering over the compost are fungus gnats, a symptom of permanently wet surface compost. Watering from below and letting the top 2cm dry out usually sorts them within a fortnight.

Sticky leaves with fine webbing points to red spider mite, which thrives in hot, dry, still air. Wash the plants under a lukewarm tap, keep the compost lightly moist, and move them somewhere with more air movement.

Finally, take cuttings. A supermarket basil will root in a glass of water on the sill in about ten days, and mint roots even faster. A few cuttings in late summer means you begin next spring with plants already underway rather than a shopping list.