How to grow a basil bush

Forget the scrawny supermarket stuff, says Monty Don, plant your own basil and you can grow enough to make pesto to last you into winter

NO taste is more typically Italian than pesto made from fresh basil, garlic, pine nuts, olive oil and Parmesan cheese. I love it with pasta, potatoes, lettuce or just spread on bread. Delicious. There is a tendency, certainly among the metropolitan foodie classes, to fetishise pesto and hunt out the original or perfect recipe, but it is worth remembering that it simply means ‘paste’ and all Italian recipes for it are created within individual families and can vary hugely.

We make pesto with both parsley and rocket as well as basil, and happily substitute walnuts for pine nuts and use whatever hard cheese is to hand. All variations can be very good indeed. But in the end it is that pungent, musky, oily taste of basil that is so good and which combines so well with garlic, oil and the slightly burnt taste of the roasted pine nuts.

So I have grown lots of basil for the past 20 years – indeed, it is one of our major midsummer crops – and although it is best eaten fresh, pesto will freeze well (but leave out the cheese, which can then be added after it has defrosted) or store in a Kilner jar so that rich taste of summer sun can be enjoyed in the darkest days of winter. My guess is that most people only come across fresh basil in those little pots crammed with tiny seedlings that can be bought from supermarkets. This is certainly better than nothing but not even remotely as good as any gardener with a greenhouse, cold frame or even a very sunny corner can grow for themselves at home – at a fraction of the price.

The secret of good basil is to grow it fast while allowing the plants to become as large as possible without the leaves losing their freshness. When fully mature and ready for picking, a healthy basil plant should be about 30-45cm (12-18in) tall and half that in diameter. They are lusty plants and should not be crammed into a tiny space if they are to realise a fraction of their possible flavour or abundance.

I sow my first basil seeds in March and germinate them in a heated greenhouse. A warm windowsill would do just as well. As soon as they are large enough to handle I prick the seedlings out into plugs and grow them on in the greenhouse. If need be I pot them on again into individual 7.5cm (3in) pots. The idea is to keep their growth unchecked. Above all they like warmth, moisture and a rich but well-drained soil. As a guide they usually do fine growing alongside tomatoes – although this year I have grown some in cold frames, where the heat and humidity is greater than in the greenhouse where the tomatoes are, and the basil has absolutely loved this. I have cut the plants right back and should get another crop before lifting the plants and replacing them with a final, late batch.

I always grow some outside but unless the weather is hot for at least three weeks and last year it was in late June and early July – the plants are smaller, yellower, tougher and not nearly as good to eat as the protected plants.

If you sow some seeds now, pricking them out into individual 7.5cm (3in) pots in around four weeks time, and keeping them well-watered and as warm and sunny as possible, then you could still grow a decent crop to make your own pesto – but this is something you must do soon because the light and heat are already fading and basil is one of the first plants to react badly to cold weather. Once the temperature drops below 10°C the leaves become leathery and the lets This is trained Cut this back to a tiniest touch of frost reduces them to black rags.