This is the moment in the greenhouse – with warmer nights finally arriving, the soil temperature rising, the light long and generous – when basil stops being a struggle and becomes worth growing. Even if you haven’t started yours yet you can get it underway in June and you’ll be cutting handfuls of the stuff by July, enough to make pesto by the bowlful, or to scent a tomato salad, or just to bruise between your fingers for the smell of it.
I grow basil in the greenhouse rather than outside because basil is very much a warmth loving plant that will never quite forgive Britain for not being Italy. It sulks in cold wind and blackens at the first hint of a chill. Under glass, though, it is a different plant entirely, lush and bushy and brilliantly fragrant, exactly as it should be.
One of my favourite tricks, and one I’d recommend to anyone, is buying those pots of living basil from the supermarket. You know the ones, a tightly packed clump of seedlings all crammed together into a small plastic pot, sold cheaply and designed to sit on a kitchen windowsill for a fortnight before giving up. Those pots contain not one plant but many, sometimes twenty or thirty seedlings all crammed together. Water the pot well and then tease them apart gently, roots and all, and pot them up separately or in small groups of three or four into good compost. Water them in, put them in the greenhouse, cut them back to just above a pair of leaves (and eat the cuttings) and within a few weeks they will have transformed into strong, generous plants that bear no resemblance to the sad little supermarket pot they came from. It works really well, and is much cheaper than buying individual plants from a garden centre, and much faster than starting from seed.
When it comes to varieties, it is worth going beyond the standard sweet basil, good as it is, and for this you will need seed. I love Greek basil, which forms a neat little dome of tiny leaves, incredibly pretty and intensely flavoured, and compact if space is tight. Purple basil, dark as a blackberry, and beautiful in a salad, is worth growing for the colour alone. And then there is Thai basil, with its strong anise notes and sturdy leaves that hold up well in cooking. Lemon basil is another favourite, lighter and citrusy, and really wonderful with fish.
Through July and August the main job will be pinching out. This is easily done when you are harvesting regularly, just take the top, most tender leaves each time and you will encourage the plant to bush out lower down the stem. Also watch out for any sign of flowering and pinch out flowers when you see them or you will lose the lovely tenderness of the leaves. Let it flower and it will put all its energy into seed and the leaves will turn bitter and sparse. Pinching out keeps the plant bushy, delays the end of the season, and means more leaves for longer. Stay on top of it and the plant keeps giving.
When September arrives and the nights begin to cool, I bring the most vigorous plants into the house and place them on a sunny windowsill somewhere warm to extend the season a little further. Outside, basil’s days are numbered once the temperature drops but under glass, and eventually indoors, a good plant can keep going well into autumn.
Start now and tend it faithfully, and basil will repay you generously for many months to come.