Why the windowsill is the best spot in the house

If you have a windowsill that catches a few hours of daylight, you have everything you need to grow your own salad. Loose-leaf lettuce and rocket are two of the most rewarding crops a small-space gardener can sow, and they happen to be perfectly suited to life in a pot indoors. They grow fast — often ready to pick within four to six weeks of sowing — they don't need deep roots, and they keep producing for weeks if you harvest them sensibly.

Aim for a spot that gets at least four to six hours of decent light a day. A south-facing sill will give you the quickest growth but can become uncomfortably hot between June and August, which encourages plants to bolt. An east- or west-facing window is often easier to manage, giving gentler morning or afternoon sun without the midday scorch. If your only option is a north-facing sill, you can still grow rocket and mizuna reasonably well, but expect slower, looser growth and sow a little more thickly to compensate.

Choosing pots and compost

Salad leaves are shallow-rooted, so you don't need anything grand. A pot 15–20cm deep and 20–30cm across will comfortably hold a handful of plants and give you a decent bowlful at each cut. Drainage matters far more than size: without holes in the base, roots sit in stagnant water and rot within days.

• Containers: terracotta, plastic pots, old mushroom trays, ice-cream tubs, or a rectangular windowsill planter — all fine, provided you drill or punch drainage holes.
• Saucers: useful to protect the sill, but empty them after watering so roots aren't left standing in water.
• Compost: a peat-free multipurpose compost works well. Mix in a handful of perlite or horticultural grit per pot to keep it open and free-draining.
• Depth: fill to about 2cm below the rim, leaving room to water without compost spilling over the edge.

Fresh compost already contains enough nutrients for the first few weeks. Don't be tempted to reuse old compost from last year's tomatoes — it will be exhausted and may harbour pests.

Which varieties actually work

Stick to loose-leaf types and cut-and-come-again crops. Hearting lettuces such as iceberg or butterhead need more room and much more time before they're worth eating.

• Loose-leaf lettuce: 'Salad Bowl', 'Red Salad Bowl', 'Lollo Rossa' and 'Catalogna' are reliable, colourful and quick.
• Rocket: wild rocket is punchier and slower to bolt than salad rocket; both are excellent sown thickly.
• Extras worth trying: mizuna, red mustard, corn salad, pak choi and baby spinach leaves all behave similarly in a pot.

Mixing two or three varieties in one container gives you a varied harvest from a single sowing — and looks rather good on the sill.

Sowing for a steady supply

Sow thinly across the surface of damp compost, then cover lightly. Lettuce wants about 3–5mm of compost over the seed; rocket barely needs any, just a dusting. Germination is quickest at around 15–18°C, and you should see seedlings within seven to ten days.

The secret to a continuous supply is succession sowing. Rather than filling one enormous pot, sow a small pot every two to three weeks from early spring through to late summer. That way you always have younger plants coming on as older ones tire. Once seedlings are up, thin them to roughly 3–5cm apart — and eat the thinnings, which are delicious.

Watering and keeping them healthy

Keep the compost consistently moist but never soggy. Windowsill pots dry out fast, especially in summer and especially near radiators in winter, so check daily by pressing a finger into the surface. Water in the morning where you can, and use a small watering can or jug with a fine rose to avoid flattening the seedlings.

• Feeding: after three or four weeks, start giving a weak liquid feed — seaweed or a general-purpose tomato feed at half strength, once a week.
• Light: turn pots a quarter-turn every few days so plants grow straight rather than leaning towards the glass.
• Pests: aphids and whitefly are the usual culprits. A firm squirt of water from a spray bottle dislodges them; inspect the undersides of leaves weekly.
• Bolting: if leaves turn bitter and a flower stem appears, the plant has run to seed. Move it out of direct sun, keep picking, and sow a fresh pot.

Cut-and-come-again harvesting

Start picking when leaves are around 8–10cm tall. Take the outer leaves first, snipping them a couple of centimetres above the compost and leaving the growing crown in the middle untouched — this is what keeps the plant producing. For rocket, you can simply shear the whole pot back to 2–3cm and it will regrow within a fortnight. Never strip more than a third of the foliage at once.

A well-tended pot will give you four to six cuts over eight to ten weeks before it starts to flag. Wash your leaves, spin or pat them dry, and use them the same day for the sweetest flavour. Sow a new pot the moment an old one slows down, and you need never buy a bag of limp salad again.