From Seed to Pesto: How to Grow Basil

The challenge… how to grow basil! With basil in our climate isn’t that it won’t grow. It will, and quite vigorously at that. The issue is timing and temperature. Basil is a tender annual that originates from tropical regions of Asia, which means it absolutely despises cold weather and won’t tolerate frost. I’ve seen perfectly healthy plants turn black and mushy overnight after an unexpected May chill, so understanding our British growing season is absolutely crucial.

The good news? Between late May and September, conditions are usually brilliant for basil, and you can keep harvesting continuously if you know how to encourage bushy growth rather than letting it bolt straight to flower.

How to Grow Basil

Before you start, gather these essentials. I’ve found that having everything ready makes the process much smoother, particularly when you’re sowing seeds which need prompt watering.

Another guide you may like is our guide on from seed to plate: growing spring greens all winter.

Seeds or Seedlings

You’ll want to choose between starting from seed or buying young plants. Sweet basil (Ocimum basilicum) is the classic variety, brilliant for general cooking and pesto. Purple basil adds colour to salads, whilst Thai basil has a distinct anise flavour that’s proper lovely in Asian dishes. Greek basil grows in compact mounds with tiny leaves, perfect for small pots on sunny windowsills.

I prefer starting from seed because it’s more economical and you get far more plants, but if you’re new to growing herbs, buying a couple of established seedlings from a garden centre or local market gives you a head start. Just inspect them carefully for yellow leaves or signs of stress before purchasing.

Growing Medium and Containers

Basil needs well-draining, nutrient-rich compost. I use a multipurpose peat-free compost mixed with about twenty per cent horticultural grit or perlite to improve drainage. This is important because basil roots detest sitting in waterlogged soil, which leads to root rot and fungal issues.

You might also find from seed to pod: growing sugar snap peas that actually snap helpful.

For containers, anything with drainage holes works. I’ve successfully grown basil in terracotta pots (which dry out faster, so need more frequent watering), plastic pots (which retain moisture better), and even recycled yoghurt pots with holes punched in the bottom. If you’re planting outdoors, choose containers at least fifteen centimetres deep. For windowsill growing, smaller pots work fine, but you’ll need to water more often.

Additional Equipment

You’ll also need a watering can with a fine rose (the sprinkler attachment), labels if you’re growing multiple varieties, and ideally a propagator or clear plastic bag for seed starting. A spray bottle is useful for misting seedlings. If you’re growing indoors year-round, a sunny windowsill or grow light makes all the difference during our darker months.

Step-by-Step Instructions

Sowing Basil Seeds

I always wait until late April at the earliest to sow basil seeds, and honestly, mid-May is safer in most parts of Britain. If you’re in Scotland or northern England, early June might be more sensible. The soil temperature needs to be consistently above 15°C for good germination, and night temperatures shouldn’t drop below 10°C.

Fill small pots or seed trays with your compost mix, water thoroughly, and let it drain. Sprinkle seeds thinly on the surface. Basil seeds are tiny, so take your time. Cover them with just a few millimetres of compost. They need some light to germinate, so don’t bury them deeply.

Place the pots in a propagator or cover with a clear plastic bag to maintain humidity. Put them somewhere warm, ideally between 20-25°C. A heated propagator is brilliant, but I’ve had success on top of the fridge or near (not on) a radiator. In my experience, germination takes seven to fourteen days depending on temperature.

Caring for Seedlings

Once you see green shoots, remove the covering immediately. Basil seedlings are prone to damping off (a fungal disease that causes seedlings to collapse), so good air circulation is essential. I’ve lost entire trays to this, and it’s frustrating.

Move seedlings to a bright, warm spot. A south-facing windowsill is ideal. Water from below by placing pots in a tray of water for a few minutes, then letting them drain completely. This keeps the leaves dry and reduces fungal problems.

When seedlings have two sets of true leaves (the second set that appears, after the initial seed leaves), thin them out or prick them out into individual pots. I usually transplant them into nine-centimetre pots at this stage. Handle them by their leaves, not stems, as the stems are delicate and easily damaged.

Transplanting and Positioning

Basil needs warmth and sunshine to thrive. In Britain, this means a south-facing position is best. I grow mine in several locations: on my kitchen windowsill for easy access when cooking, in pots outside my back door during summer, and in the greenhouse where they absolutely flourish.

Don’t rush to move plants outdoors. Wait until all risk of frost has passed, typically late May or early June. Even then, harden them off gradually over a week by moving them outside during the day and bringing them in at night. Sudden temperature changes will shock them.

Basil can be grown in the ground if you have a sheltered, sunny spot, but I prefer containers. They’re easier to move if the weather turns nasty, and you can bring them indoors as autumn approaches. Space plants about twenty centimetres apart if planting multiple ones together.

Watering and Feeding

Here’s where many people go wrong: basil likes consistent moisture but hates wet feet. The compost should be moist but never soggy. I stick my finger into the soil up to the first knuckle. If it feels dry, I water. If it’s still damp, I wait.

Water in the morning rather than evening. This gives leaves time to dry before cooler night temperatures, reducing fungal problems. Always water the soil, not the leaves. I’ve found that splashing water on the foliage, especially in humid conditions, invites trouble.

Feed every two weeks once plants are established. I use a liquid seaweed feed diluted to half strength. Basil isn’t a heavy feeder, and too much nitrogen produces lots of leafy growth but reduces the essential oil content that gives basil its flavour. You want healthy growth, not forced, sappy stems.

Harvesting to Encourage Growth

This is the most important technique for productive basil plants. Never just pick individual leaves from the bottom. Instead, pinch out the growing tips regularly. When your plant has six to eight leaves, pinch out the top two sets. This forces the plant to branch out from lower down the stem.

I harvest little and often, which keeps plants bushy and delays flowering. Cut just above a pair of leaves, and the plant will produce two new stems from that point. Do this every week or so, and you’ll have a proper bushy plant rather than a single leggy stem.

Flower buds will appear, especially as days get longer. Pinch these out immediately. Once basil flowers, leaf production slows and the flavour becomes bitter. I’m vigilant about removing flower spikes as soon as I spot them. If you want seeds for next year, let one or two plants flower at the end of the season.

Common Mistakes to Avoid

Planting Out Too Early

The biggest mistake I see, and one I’ve made myself when I was impatient, is putting basil outside too soon. Even a chilly night in early May can severely set back growth. Those supermarket basil pots people buy in March? They’re meant for indoor windowsills, not outdoor planting. I’ve watched neighbours plant theirs out in April only to have them turn yellow and stop growing for weeks.

Wait for genuinely warm, settled weather. Late May is the earliest for southern England, and early June is safer further north. If you’re unsure, keep plants in pots that you can move indoors on cold nights. It’s better to wait an extra fortnight than lose plants to cold damage.

Overwatering and Poor Drainage

Basil roots need oxygen as much as they need water. Waterlogged compost drowns roots and creates perfect conditions for fungal diseases. I’ve killed more basil through kindness (too much watering) than neglect.

Always ensure containers have drainage holes. If you’re using decorative pots without holes, either drill some or use them as outer pots with a draining inner pot that you can lift out. Water thoroughly when needed, but let the top couple of centimetres of compost dry out between waterings. In hot weather, this might be daily. In cooler conditions, perhaps every three or four days.

Not Pinching Out Regularly

If you let basil grow into a single tall stem, you’ll get very little harvest before it flowers and dies. Regular pinching creates a bushy plant with multiple stems, each producing leaves. I aim to harvest something from each plant weekly, even if it’s just the growing tips. This constant pruning is what keeps production going.

Ignoring Pests

Aphids love basil, particularly when plants are stressed. Check the undersides of leaves regularly. I’ve also had problems with slugs eating seedlings and occasionally red spider mite in the greenhouse during hot, dry spells. Dealing with pests early, before populations explode, is much easier than trying to save heavily infested plants.

Expert Tips

Succession Planting for Continuous Harvest

Rather than sowing all your basil at once, I sow small batches every three to four weeks from May through July. This gives me a continuous supply of young, vigorous plants. Older plants naturally decline and become woody as the season progresses, so having younger plants coming along ensures I’m never without fresh basil.

Greenhouse Growing

If you have a greenhouse or polytunnel, basil absolutely loves it. The extra warmth and protection from wind and rain produces stronger plants with better flavour. I’ve grown basil in my greenhouse from April through October with proper harvests. Just watch for red spider mite in hot weather and ensure good ventilation to prevent fungal issues. The plants grow noticeably faster and larger than outdoor ones.

Companion Planting

I grow basil alongside tomatoes, both in the greenhouse and outdoors. They have similar growing requirements (warmth, consistent moisture, sunshine), and there’s some evidence that basil may help deter whitefly from tomatoes, though I’ve not noticed a dramatic difference myself. What I have noticed is that having basil right next to tomatoes is convenient when I’m making pasta sauce.

Preserving Your Harvest

Come late August, I usually have more basil than I can use fresh. Freezing preserves the flavour better than drying. I make pesto and freeze it in ice cube trays, then transfer the cubes to freezer bags. Alternatively, blend fresh basil leaves with a little olive oil and freeze in small portions. Dried basil loses much of its flavour, but if you want to try it, hang small bunches in a warm, airy spot out of direct sunlight until crispy, then crumble into jars.

Indoor Winter Growing

Basil is challenging to grow indoors during British winters because of low light levels. I’ve had limited success keeping plants alive on a south-facing windowsill, but growth is slow and flavour is weaker. A grow light makes a significant difference. Alternatively, treat basil as a summer crop and use preserved basil through winter. That said, if you have a bright, warm spot, it’s worth trying. Just lower your expectations for winter productivity.

Frequently Asked Questions

Can I grow basil from cuttings?

Absolutely, and it’s remarkably easy. Take cuttings about ten centimetres long from healthy stems, remove the lower leaves, and place in a glass of water on a sunny windowsill. Roots appear within a week or two. Once roots are a couple of centimetres long, pot up into compost. I do this in mid-summer when plants are growing vigorously. It’s a quick way to propagate favourite plants, and the cuttings often root faster than seeds germinate.

Why does my supermarket basil always die?

Those pots from supermarkets contain dozens of seedlings crammed together, competing for light, water, and nutrients. They’re grown quickly in perfect conditions and aren’t hardened off for home growing. When you get one home, tip it out and you’ll see it’s actually multiple plants. Separate them carefully, pot them individually in proper compost, and they’ll do much better. Even then, they’ve often been stressed, so don’t expect miracles. Growing from seed gives you stronger plants.

What are the small holes in my basil leaves?

This is likely flea beetle damage. These tiny jumping beetles are common pests that chew small round holes in leaves. They particularly affect plants that are stressed or growing slowly. The damage is usually cosmetic rather than fatal. Keeping plants well-watered and growing strongly helps. You can also cover plants with horticultural fleece to exclude the beetles, though this is fiddly for something you’re harvesting regularly. I’ve found that healthy, fast-growing plants tolerate flea beetle damage without significant problems.

Can basil survive outdoors through winter?

No, basil is a tender annual that won’t survive frost. Even without frost, temperatures below about 10°C cause significant damage. As autumn approaches and temperatures drop, basil slows down, turns yellow, and eventually dies. You can bring pots indoors before the first frost and keep them on a sunny windowsill, which sometimes extends the harvest by a few weeks, but eventually the plant will decline. It’s better to save seeds or take cuttings in late summer if you want to preserve particular varieties.

How do I know when to harvest basil?

You can start harvesting once plants have at least six sets of true leaves, usually six to eight weeks after sowing. Always pinch out the growing tips rather than picking lower leaves. This encourages bushier growth. Harvest in the morning after any dew has dried but before the heat of the day, when essential oil content is highest. The best time for maximum flavour is just before the plant flowers, but with regular harvesting to prevent flowering, you can maintain good flavour throughout the growing season.

Why is my basil turning yellow?

Yellow leaves can indicate several problems. Overwatering is the most common cause, leading to root rot and nutrient deficiency. Check that your compost isn’t waterlogged and that containers drain properly. Alternatively, plants may need feeding if they’ve been in the same compost for months. Cold temperatures also cause yellowing, particularly if plants have been exposed to chilly nights. Occasionally, yellowing indicates pest problems like aphids or spider mites. Check leaves carefully, especially undersides, for tiny insects. Addressing the underlying cause usually allows plants to recover, though badly affected leaves won’t turn green again.

Conclusion

Growing basil successfully in Britain is absolutely achievable once you understand its needs for warmth, sunshine, and careful watering. I’ve found that treating it as the tender, heat-loving plant it is, rather than expecting it to behave like hardy British herbs, makes all the difference. Start seeds indoors or wait until late May for outdoor sowing, choose a sunny spot, and harvest regularly by pinching out growing tips. The reward is months of fresh, aromatic leaves that taste infinitely better than anything you’ll buy in shops.

The techniques I’ve shared come from plenty of trial and error, including dead seedlings and disappointing harvests. But basil is forgiving if you get the basics right, and even a few plants on a sunny windowsill will provide enough for regular cooking. Whether you’re making classic pesto, adding torn leaves to tomato salad, or experimenting with Thai or purple varieties, home-grown basil brings genuine flavour and satisfaction to your kitchen. Give it the warmth and attention it needs, and you’ll wonder why you ever bought those expensive little pots that last three days before collapsing.

Author: Megan Walker

Megan focuses on seasonal food, kitchen garden growing, and how households can reconnect with where their food comes from. Her writing blends practical growing advice with ideas for cooking and eating in season. With a passion for fresh ingredients and sustainable living, Megan’s articles help readers make the most of local produce while supporting British farms.