Gardening: Herb your enthusiasm

Parsley and basil are the herbs we use most in our house and every year I have a vision of non-stop supplies of both. It's never yet happened, though once I managed to keep some basil plants going until after Christmas on the kitchen windowsill. That's where they had first germinated so they didn't do much living, those basils. But at least they were warm. And because they were in front of me every day as I trolled around the sink, they never went short of water either.

When our windowsill basils finally began their drift towards the compost heap, I packed the last pathetic leaves into a jar, and poured olive oil on top of them. If you leave the mixture to steep for two weeks, you have a pleasantly scented olive oil to use in salad dressings. You can enjoy the ghost of the plant, if not its substance. Even the most hastily constructed salad or dish of pasta is transformed by a whiff of basil, and gardeners have at last discovered that in the right conditions, it's not difficult to grow. Even five years ago, it was unknown in any seed company's list of top 10 varieties. Now it's a regular.

I've tried growing basil in three different ways: in the open ground, in the cold frame and on the kitchen windowsill. The last has been the best for me, but that's because I don't have a greenhouse or a polytunnel. People who do favour those rather than open ground. That's because basil was born in India (with cousins in Thailand) and is used to a climate altogether warmer than ours. It's been associated with Italy for so many thousands of years, we tend to think of it as a Mediterranean native, but it's not. Italy evidently suits it though and one of the best has an Italian name, 'Genovese' – Ocimum basilicum 'Genovese' if we're being formal – which suggests that it was selected and developed there.

Before seed merchants, before mail order, before the internet, seeds had to be saved from your own crops. In each small village and valley, vegetable growers selected seed from plants that had done particularly well for them. Over hundreds and hundreds of years, the plants grown from these different seeds start to diverge. A basil (or broccoli) in one village developed slightly different characteristics to one grown where the aspect or soil had favoured other traits. Geneticists call them "landrace" varieties.

Perhaps in another thousand years, basil, now it's arrived over here, will have developed a greater resistance to cold and become our very own landrace variety – Ocimum basilicum 'Britannia'. At the moment though, it doesn't have it, so needs protection either end of the growing season. That's why it pays to be patient. If you choose the windowsill, you can sow basil seed now. If you sow outside, you must wait till the beginning of June.

Use ordinary multipurpose compost, but make sure it is fresh. Sprinkle a tiny pinch of seed on top of a three-inch pot filled with compost. The typical Mediterranean sweet basil (Ocimum basilicum) has bigger seeds than the sacred or Thai basil (Ocimum sanctum) which generally makes a shorter plant. Cover the seeds with a fine layer of vermiculite. Water the pot carefully, then cover it with a piece of glass or clingfilm until the seedlings emerge. This shouldn't take more than one to two weeks at about 20C, a typical temperature on a kitchen windowsill.

Let them grow on in the original pot, giving them plenty of light and watering in the morning rather than the evening. Basil plants hate being wet at night. When the seedlings seem sturdy and reasonably well established, tip the whole lot out on newspaper and tease the plants apart, replanting them two at a time in 7-10cm pots.

Once pricked out like this, our plants stay in their pots and spend their whole lives among the stray buttons, screws, corks and safety pins that experience has taught should never be thrown away. From time to time the pots spend an hour soaking in the sink, the water beefed up with a touch of Baby Bio. Pinch out the tops of the plants to make them bushy. The plants try to flower but you must pinch out those too to keep up a good supply of leaves.

If you've got a greenhouse, or a polytunnel, you can sow seed under cover now in lengths of guttering ready to plant out in June when the soil has warmed up. Sprinkle it as thinly as you can and be prepared to thin out the seedlings if necessary. When the seedlings are about 5cm tall (and provided the weather is on your side), carry out the guttering (a two-man job) and slide the U-shaped tube of soil out of the guttering into a shallow trench made the same width and depth. Do it in stages, settling one length in before pushing out the next, like toothpaste from a tube. But remember that basil hates growing in temperatures that wobble too much between highs and lows and a cold night will kill it off altogether.

Suffolk Herbs offer 20 different kinds of basil in their new catalogue – a sure sign that this herb is now as much about cult as cultivation. I love the stuff, but a windowsill can't offer room for more than three different kinds in a summer. You need 'Sweet Genovese' (Suffolk Herbs £1.29) for the authentic Italian swish it gives to food. Avoid types with lettuce-like leaves, which do not have such a good flavour.

The beautiful purple-leaved kinds aren't as well-flavoured nor so vigorous as ordinary sweet basil, but the leaves are very beautiful, mixed with tomatoes in a salad. Choose 'Purple' or 'Purple Ruffles' (both Suffolk Herbs £1.29). Your third choice might be a variety with a very particular tang: 'Horaphu Rau Que' (Suffolk Herbs £1.49) is a favourite from Thailand, grows to about 37cm and tastes of aniseed. My third choice, though, would be a small-leaved Greek basil, only 22cm tall and wonderful lined out in small terracotta pots, when they look like miniature pieces of topiary.

Outside, you can sow contrasting types side by side to make a corduroy patch of perhaps half a dozen different kinds. Or you could trace out a circle, divide it into eight segments and broadcast different seed over each of the eight portions.

Alternatively, you can raise plants in separate pots, as if you were growing them inside and then transplant them outside when they are already well grown. Water them in well, remembering that morning is better than evening. Choose a warm, sheltered sunny place and after you've sown your seed, lay fleece over the seedbed to prevent cats (or birds) scratching it up. If nights seem unseasonably chilly, leave the fleece in place as the seedlings grow, or cover them with cloches.

Outside, basil plants must be gradually acclimatised. If you get it wrong, the leaves turn a dramatic black overnight. Because our weather is so unpredictable (frosts in June are not unknown) you may need to fiddle with covers and cloches, providing protection at night, but plenty of light and air during the day. If you sow direct into the soil, you will also need to thin the seedlings as they develop so that they are eventually about 15cms apart.

Suffolk Herbs, Monks Farm, Coggeshall Road, Kelvedon, Essex CO5 9PG, tel: 01376 572456, e-mail: sales@suffolkherbs.com, or visit suffolkherbs.com