Start With the Right Windowsill

Almost every kitchen in Britain has a windowsill doing nothing more than holding a jar of old pens. Before you buy a single seed packet, work out which way that sill faces, because herbs are fussy about light in a very straightforward way. A south or south-west facing window is the jackpot: you will get six or more hours of sun a day, which is exactly what basil and chives need to grow thick and green rather than pale and leggy. East-facing sills are decent too, with strong morning light and a gentler afternoon. North-facing windows are the tricky ones. You can still grow mint there, and it will do fine, but basil will sulk and stretch towards the glass.

One warning before you commit: herbs on a windowsill sit directly above a radiator in most homes. Central heating dries the air and cooks the compost from below. If your only sunny sill is above a radiator, either turn that radiator off, or accept that you will need to water more often and move the pots a few centimetres forward onto a raised tray.

The Three Herbs Worth Starting With

You can grow almost anything on a sill, but beginners do best with plants that forgive a missed watering and reward steady picking.

• Basil. Buy a supermarket pot and you have instant success, though those pots are crammed with dozens of seedlings competing for water. Split them into two or three pots immediately and they will reward you within a fortnight. Sow seed from April to July for the best results.
• Mint. Ferociously easy and almost impossible to kill. Keep it in its own pot, always, because it sends runners out sideways and will smother anything sharing its compost. Spearmint suits cooking; Moroccan mint makes better tea.
• Chives. The most useful windowsill herb in a British kitchen. They grow from seed or from a supermarket pot, they tolerate less-than-perfect light, and you snip them with scissors rather than picking leaf by leaf. They also come back year after year if you keep them going.

If you have room for a fourth pot, flat-leaf parsley and thyme are both worth a go, but neither is as forgiving as the trio above.

Pots, Compost and Drainage

Size matters more than most people expect. A herb in a tiny 9cm pot dries out in a single warm afternoon and never gets the root room to grow properly. Aim for pots around 15–18cm across, with a decent depth. Terracotta looks lovely and lets roots breathe, but it wicks moisture away from the compost, so plastic or glazed ceramic is a kinder choice for a sunny sill.

Use a peat-free multipurpose compost rather than soil from the garden, which is heavy and full of weed seeds. Every pot needs a drainage hole, and every pot needs a saucer underneath it, or you will be scrubbing a watermark off the sill for months. If you would rather not have saucers on show, stand the pots on a shallow tray of gravel — it catches drips and lifts the pots slightly out of standing water.

How to Water Without Drowning Them

Overwatering kills more windowsill herbs than neglect ever does. The classic mistake is a small daily splash, which keeps the top of the compost damp while the roots below sit in a soggy, airless layer. That is how you get yellowing leaves, fungus gnats and a plant that collapses for no obvious reason.

Water properly instead: push your finger about 2cm into the compost. If it feels dry at that depth, water steadily until it runs out of the bottom, then stop and let the pot drain. If it feels damp, walk away and check again tomorrow. In summer you might water every two or three days; in a cold January you might water once a week or less. Chives and mint prefer to stay slightly moist; basil and thyme would rather dry out a little between waterings. Feeding matters too, but gently — a diluted liquid feed every fortnight from spring to late summer is plenty. Too much feed makes lush, soft growth with no flavour.

Harvesting Is What Keeps Them Bushy

This is the bit beginners miss, and it is the secret to a plant that keeps producing instead of turning into a single sad stalk. Herbs respond to being cut. Every snip tells the plant to branch out sideways, so regular picking gives you a denser, fuller, more useful plant.

With basil, never strip single leaves from the bottom. Instead, pinch out the growing tip just above a pair of leaves, and two new shoots will appear from that point. Do this every week or so during the growing season and you will get a bush rather than a beanpole. Take out any flower buds the moment you see them, because once basil flowers it stops producing leaves and starts dying back.

With mint, cut whole stems about 5cm from the base rather than picking leaves off the top. Chives want the opposite treatment: snip the outer leaves down to about 3cm from the compost with sharp scissors, never tugging, and leave the centre to regrow. As a rough rule, never take more than a third of the plant at once.

Pests, Winter and Troubleshooting

The two problems you are most likely to meet are greenfly on basil and fungus gnats hovering over wet compost. Greenfly can be knocked off with a firm spray of water from a mister, or wiped away with your fingers. Gnats are a sign of overwatering — let the top layer of compost dry out and they usually disappear. A weak solution of washing-up liquid in a spray bottle deals with most small infestations without any fuss.

Winter is the real test. Light levels drop, growth slows, and your herbs need far less water. Move pots to the brightest sill you have, stop feeding altogether, and water sparingly. Basil in particular rarely survives a British winter on a windowsill; it is cheaper and kinder to let it finish, then sow fresh in spring. Mint and chives will often die back completely and reappear in March, so don't tip them out in a panic. Give them a light trim, keep them barely moist, and wait.