How to Grow Basil at Home in the UK

Basil is the perfect first herb: fast, fragrant, and happy on a bright windowsill even when it's grey outside. A few pots on a kitchen sill will scent the whole room, and the moment you tear a leaf into a salad or a bowl of pasta you'll wonder why you ever bought those sad cellophane bags from the supermarket. It's a brilliant gateway into windowsill growing for nervous beginners.

The one thing to understand from the start is that basil is a creature of warmth. It comes from hot Mediterranean and tropical climates, and it sulks the moment the temperature drops. That single fact explains almost everything about growing it in the UK: sow it warm, keep it bright, and don't rush it outdoors until summer arrives. Get those basics right and a single windowsill will keep you in fresh leaves for months. This guide walks you through the whole journey, from a pinch of seed to a jar of homemade pesto.

Choosing a variety

There's far more to basil than the standard supermarket pot. UK seed suppliers stock a lovely range, and a couple of small packets will give you flavours and colours you'll never find on a shelf.

Sweet / Genovese — the classic

This is the basil of Italian cooking: large, soft, aromatic leaves with that unmistakable warm, clove-and-pepper scent. 'Sweet Genovese' is the variety for pesto, tomato salads and pasta, and it's the most widely available and forgiving type for beginners. If you only grow one basil, make it this one.

Greek bush basil — compact and tidy

Greek or 'bush' basil forms a neat dome of tiny leaves, wonderfully suited to a windowsill. The flavour is a touch milder and spicier, but the plant is naturally bushy, slower to bolt, and handsome on a kitchen sill. A great choice where space is tight.

Purple basil — for colour

Varieties like 'Purple Ruffles' and 'Dark Opal' have deep burgundy leaves that look striking in pots and salads, with a slightly more clove-like flavour. It can be fussier and slower than green types, but it's worth growing for the colour alone — children love it.

Thai basil — aniseed and spice

Thai basil has narrow, tougher leaves, purple stems, and a distinctive aniseed-liquorice flavour that's essential in stir-fries, curries and pho. It stands up to the heat of cooking far better than sweet basil. If you cook South-East Asian food, this is a must.

Lemon basil — citrus notes

Lemon basil carries a bright citrus scent over the usual basil flavour, lovely with fish, in dressings and in cold drinks. Like the others it's a tender annual and grows in exactly the same way — a fun one to grow alongside the classics.

You can buy seeds from Suttons, Thompson & Morgan, and Dobies. For more flavour ideas and which herbs earn their place in a small kitchen garden, see our guide to the best herbs for cooking.

Why basil needs warmth

Almost every basil failure in the UK comes back to cold. Basil is a tender annual — it completes its whole life in a single season and has no frost-hardiness whatsoever. A light frost will blacken it overnight, and even chilly, sub-10°C nights check its growth, yellow the leaves and make it sulk.

This is why timing matters more for basil than for hardier herbs. There's genuinely no rush to sow in February: seed sown into cold compost simply rots, while a sowing made in warm April conditions germinates fast and often overtakes it. The seed needs around 18–20°C to come up reliably, which is why a warm windowsill is the natural home for British basil for most of the year.

Where Mediterranean herbs like rosemary, thyme and oregano are tough, woody perennials that shrug off a British winter, basil is the soft, tender exception in the family — see our guide to Mediterranean herbs for how the hardier herbs differ. Keep this one warm, and everything else falls into place.

Sowing basil

Basil is one of the easiest things you'll ever sow, provided you keep it warm. Sow indoors from March through to July.

What you need — a small pot or seed tray, fresh peat-free seed or multi-purpose compost, and a warm, bright spot. A clear lid, a propagator, or a freezer bag over the pot all help hold in warmth and humidity while the seed germinates.

How to sow:

• Fill your pot with compost and water it lightly first, so you're sowing onto already-moist compost rather than soaking the seed afterwards.
• Scatter a few seeds thinly over the surface. Resist the urge to tip in the whole packet — overcrowding is the single biggest reason supermarket pots collapse so fast.
• Cover with the thinnest dusting of compost or vermiculite, just 3–5mm. Basil seed likes a little light, so don't bury it deep.
• Cover with a lid or bag and put it on a warm windowsill at 18–20°C. An airing cupboard works for germination, but move pots into the light the instant the seedlings show.

Germination is quick when it's warm — usually 5 to 14 days. Once seedlings appear, take the cover off to keep air moving and stop the compost going stale and damp.

Basil sows happily into homemade pots and modules if you want to save on plastic. Use the planting calendar tool to plan a steady succession of sowings through the season.

Potting on

Once your seedlings have their first pair of true leaves (the second pair to appear, after the rounded seed leaves), they're ready to move on into more space.

If you sowed thinly into small pots, simply thin each to the two or three strongest seedlings and grow them on as a little clump. If you sowed into a tray, lift small clumps gently — hold them by a leaf, never the fragile stem — and replant into their own 7–9cm pots of fresh compost. Water them in and return them to the brightest windowsill you have.

The same trick rescues a supermarket basil pot. Those are jammed with dozens of seedlings fighting over a thimble of compost, which is exactly why they keel over within a week of coming home. Tip the pot out, split the rootball into three or four smaller clumps, and pot each one up with fresh compost. Suddenly the same plant has room to breathe and will keep going for weeks.

Growing on: windowsill, greenhouse or sheltered outdoors

Basil will grow happily in three quite different places in the UK, and which you choose depends on the season and what you've got.

On a windowsill — the reliable, year-round option most people use. Choose the brightest sill you have, ideally south- or west-facing, and turn the pots every few days so the plants don't lean towards the glass. For the full picture, see our dedicated guide to basil on a windowsill.

In a greenhouse or conservatory — basil thrives in the warm, bright, sheltered conditions of a greenhouse, growing faster and bushier than almost anywhere else. It also makes a classic neighbour for greenhouse tomatoes (more on that below). A cold frame or porch can do a similar job on a smaller scale.

Outdoors in summer — only once all danger of frost has passed, which in most of the UK means late May or June. Harden the plants off first: stand them outside for a few hours a day for a week or so, bringing them in at night, so they adjust gradually. Then give them the warmest, sunniest, most sheltered spot you have — against a south-facing wall is ideal. Even so, British summers can be too cool and damp for basil to truly shine outside, so many growers keep their best plants under cover. If you're growing in pots, our guide to herbs in containers covers compost, pot sizes and drainage.

Pinching out for bushy plants

This is the single most useful habit you can learn with basil, and it's the difference between a tall, sparse, disappointing stalk and a lush, generous bush.

Left alone, basil grows straight up towards the light, pouring all its energy into one leggy stem before flowering and giving up. Pinching out — removing the very top growing tip — breaks that single line of growth and forces the plant to branch from the leaf joints below, so one stem becomes two, two become four, and the plant fills out into a dome.

How to do it — when a plant has four or five pairs of leaves, nip out the soft growing tip just above a pair of leaves. Within days, two new shoots push out from that joint. Keep doing this every time a stem gets tall and the plant stays compact and productive.

Crucially, regular pinching also delays flowering: a plant that's constantly tipped keeps making leaves rather than rushing to set seed, extending your harvest by weeks. Best of all, harvesting and pinching are the same action — every time you pick from the top, you're keeping the plant bushy.

Watering and feeding

Basil likes its compost evenly moist but never soggy, and it has firm opinions about when it's watered.

Water in the morning. Basil hates sitting in cold, wet compost overnight — a fast route to yellow leaves, root rot and disease. Morning watering lets the plant take up what it needs and the surface dry off through the day. Let the top of the compost dry slightly between waterings.

Keep the leaves dry. Water the compost, not the foliage. Wet leaves, especially overnight, invite fungal problems like downy mildew. A long-spouted can, or watering from below (standing the pot in a saucer of water for ten minutes, then draining), keeps the leaves dry.

Feed lightly. Basil isn't a hungry plant. In fresh compost it won't need feeding for the first few weeks; after that, a half-strength liquid tomato or general feed every couple of weeks through summer keeps the leaves green. Don't overdo it — too much feed gives soft, watery, less flavourful leaves.

Harvesting basil

The golden rule with basil is to harvest little and often. Frequent light picking keeps the plant young, bushy and productive, while leaving it untouched lets it grow leggy and bolt.

How to pick — always take from the top, pinching out the growing tip and the top pair or two of leaves, just above a lower leaf joint. This gives you the youngest, most aromatic leaves and triggers the branching that keeps the plant full. Never strip leaves from the bottom of the stem.

When to pick — start as soon as a plant has several pairs of leaves, and keep going through summer. A well-tended plant gives handfuls of leaves for two or three months before it tires. Pick in the morning when the aromatic oils are strongest, and use the leaves fresh — basil's flavour fades fast once cut.

Because each plant eventually slows, the way to enjoy basil all season is successional sowing: start a small new batch every three to four weeks from spring to midsummer. As one plant tires, the next comes into its prime, and you're never short of fresh leaves.

When basil flowers or bolts

Sooner or later, basil will try to flower — it's an annual, and setting seed is its whole purpose. You'll see flower spikes form at the tips, the leaves below them turn smaller and tougher, and the flavour grow bitter. This is bolting, and warm, dry, stressful conditions bring it on faster.

Pinch out flower spikes the moment you see them. Nipping off the developing buds redirects the plant's energy back into leaf growth and buys you more harvest. Combined with regular picking and steady watering, it holds off serious bolting for a good while.

Once a plant has fully bolted and turned bitter, it's largely done — which is exactly why you sowed a succession. Don't be too quick to bin it, though: a flowering basil is a lovely thing for bees, so let one tired plant flower in a sunny corner while your younger plants carry the kitchen.

Common problems

Damping-off — seedlings collapse at the base, killed by a fungus that thrives in cold, wet, airless conditions. Prevent it by sowing thinly into fresh compost, watering in the morning (and from below where you can), and giving seedlings good light and air movement.

Cold damage — yellowing leaves, blackened patches or a plant that simply stops growing usually means it's too cold. Basil checks below about 10°C and dies at the first frost. Move it somewhere warmer and brighter, and never put plants out before the last frost has passed.

Slugs and snails — outdoors, slugs adore soft young basil and can shred a plant overnight. Keep young plants up off the ground, use copper tape around pots, or grow basil under cover where slugs are far less of a problem.

Downy mildew — yellowing on the upper leaf surface with greyish, fuzzy growth underneath, encouraged by humid, still, damp conditions. Improve air flow, water the compost rather than the leaves, avoid wetting foliage overnight, and don't overcrowd your pots.

Leggy, sparse plants — almost always too little light or too little pinching. Move plants to your brightest spot and pinch out the tips regularly to force bushy growth.

Using and preserving basil

Fresh is always best with basil — it's at its most fragrant torn into a salad, scattered over a home-grown tomato, or stirred into pasta at the last moment. Add it at the end of cooking, as heat quickly drives off its delicate aroma.

When you have a glut, the classic way to capture summer is pesto: blitz a big handful of leaves with pine nuts, garlic, Parmesan, olive oil and a pinch of salt. It keeps in the fridge for a few days under a film of oil, or freezes beautifully in small tubs for ready portions all winter.

Basil also freezes well on its own. Whole leaves blacken if frozen dry, so either blanch them briefly, or — much easier — chop the leaves, pack them into an ice-cube tray, top up with water or olive oil, and freeze. Drop a cube straight into a sauce or soup as needed. Drying is less successful, as basil loses much of its character, so freezing or pesto are the routes to take.

Basil and tomatoes: the perfect partnership

Basil and tomatoes belong together on the plate, and they grow well together too. In a greenhouse or a sunny spot, a pot of basil tucked beside your tomato plants is a piece of classic companion planting: both love the same warm, bright, sheltered conditions, and many gardeners swear the basil's strong scent helps deter whitefly and other pests around the tomatoes. At the very least, you'll have both ingredients for a tomato-and-basil salad growing side by side.

It's a genuinely useful pairing for beginners, because the care is almost identical — warmth, light, steady watering, regular picking. If you're growing tomatoes too, our full guide to growing tomatoes explains how to bring the two on together.

A simple basil growing calendar

March — make your first indoor sowing on a warm windowsill if you have a bright, reliably warm spot. Cover with a lid or bag to hold in warmth until seedlings appear.

April — sow again — April sowings romp away in the lengthening light and often overtake earlier ones. Pot on March seedlings into their own pots. Use the planting calendar to plan your succession.

May — keep sowing. Start hardening off the strongest plants towards the end of the month if you want to grow some outdoors. Pinch out the tips of established plants to build bushy growth.

June — once the last frost has passed, move hardened-off plants outdoors to the warmest, sunniest, most sheltered spot, or pair them with greenhouse tomatoes. Begin harvesting in earnest.

July — peak basil. Harvest little and often, pinch out any flower spikes, and make a final sowing for late-summer leaves.

August — plants are in full flow. Keep picking and pinching. Make pesto and freeze cubes with any glut, and let one tired plant flower for the bees.

September — growth slows as nights cool. Bring the best pots back indoors to a bright windowsill to extend the season.

October onwards — outdoor basil is finished at the first frost. Indoors on a warm sill, a sturdy plant may carry on a while longer, though winter light is weak — a fresh spring sowing will always outperform it.

What to grow alongside basil

Basil is the soft, tender member of the herb family, and it sits nicely alongside its tougher Mediterranean cousins. While basil needs warmth and renewing each year, rosemary, thyme, oregano and sage are hardy perennials that come back year after year — our guide to Mediterranean herbs covers how to grow them and why they're so undemanding.

If you're putting together a kitchen-windowsill collection, our guides to growing herbs in containers and the best herbs for cooking will help you choose companions that thrive in the same bright, sunny spots. And if you're brand new to growing anything on a sill, start with our friendly introduction to windowsill growing.

Keep pinching, keep cooking, and a single pot of basil will keep you in fresh, fragrant leaves all summer long.