Why a windowsill is the perfect place to begin

A sunny windowsill is the smallest, cheapest and most forgiving garden you will ever own. There's no digging, no slug patrol and no need to own a trowel, yet you can be cutting your own basil within a few weeks of starting. The trick is to treat it like a real garden — because it is one. Plants grown indoors have the same basic needs as plants in a border: light, water, food and enough root room to breathe. Get those four things roughly right and even a north-facing flat can supply you with herbs for most of the year.

Before you buy anything, take an honest look at your sill. Which way does it face? How many hours of direct sun does it actually get in March, not just in July? Is there a radiator directly underneath it? Answer those questions first and everything else gets easier.

Pick herbs that forgive beginners

Not every herb belongs on a windowsill. The ones below cope with indoor conditions, give you something to cut fairly quickly, and won't punish a missed watering.

• Basil — the classic. It loves warmth and hates cold, soggy roots. Pinch out the growing tips regularly to keep it bushy, and remove any flower buds the moment they appear, because once basil flowers the leaves turn bitter.
• Mint — almost impossible to kill, which is exactly why it needs a pot of its own. It spreads by underground runners and will swamp anything sharing its compost. Keep it damp and harvest hard.
• Chives — tough, tolerant of a little shade and happy to be snipped with scissors. The purple flowers are edible, so don't be too quick to cut them off.
• Parsley — slow to germinate (expect three to four weeks), but a long-lived, generous plant once it gets going.
• Coriander — fast and rewarding, but it bolts in heat. Sow a small pinch every fortnight rather than one big pot.
• Thyme and rosemary — these prefer drier, grittier compost and full sun. Add them once you've got the hang of the others.

Skip anything described as a "supermarket living herb" unless you plan to split and repot it straight away. Those pots are crammed with dozens of seedlings competing for the same scrap of compost, and they rarely last more than a fortnight as they are.

Light is the one thing you can't skimp on

Herbs are sunlight addicts. Aim for at least six hours of direct light a day; a south or south-west facing sill is ideal, and an east-facing one will do for chives, mint and parsley. If your only option is north-facing, choose mint and parsley and accept slower growth — or invest in a small clip-on LED grow light, which costs very little to run and transforms a dark sill.

Turn your pots a quarter turn every few days. Without it, plants lean towards the glass and you end up with leggy, spindly stems and bare patches. Legginess is nearly always a light problem, not a feeding problem, so move the plant rather than reaching for the fertiliser bottle.

Pots, compost and drainage

Size matters more than most beginners expect. As a rough guide:

• Basil and coriander: a pot at least 15cm across, one plant per 10cm of width.
• Mint: a 2-litre pot minimum, or it'll sulk.
• Chives and parsley: 15–20cm deep, as they put down decent roots.

Every pot needs holes in the bottom and a saucer beneath. Use a peat-free multipurpose compost, and for thyme and rosemary mix in a couple of handfuls of horticultural grit or perlite so water drains freely. Terracotta looks lovely but dries out quickly; plastic holds moisture longer and is easier to keep on top of. An old yogurt pot or a tin with holes punched in the base works perfectly well — nobody is judging.

Watering without drowning them

Overwatering kills more windowsill herbs than anything else. The routine is simple: push a finger about 2cm into the compost. If it feels dry at that depth, water until a little runs into the saucer. If it feels damp, walk away.

Water in the morning where you can, pour at the base rather than over the leaves, and empty the saucer after half an hour so the roots aren't sitting in a puddle. Yellowing lower leaves and a sour smell usually mean soggy compost, not thirst. Central heating makes indoor air dry, so plants near a radiator may need checking twice as often — but move them away from the heat if you can, as basil in particular resents it.

Feeding, harvesting and keeping things going

Fresh compost contains enough nutrients for about six weeks. After that, give a diluted liquid feed every fortnight from spring to late summer, and ease off in winter when growth slows almost to a stop. Never feed a dry plant — water first, then feed.

Harvesting is what keeps these plants productive, so be brave. The golden rule is never take more than a third of the plant at once. Pinch basil just above a pair of leaves to encourage two new shoots; snip chives about 2cm from the base; strip mint from the top down. Regular cutting signals the plant to branch rather than stretch.

Finally, sow little and often. A small pot of basil or coriander started every three to four weeks will give you a continuous supply far more reliably than one enormous pot that peaks and fades. Come autumn, growth will slow and some herbs will give up entirely — that's normal, not failure. Start fresh seeds in early spring and the windowsill harvest begins again.