Wall rocket (Diplotaxis tenuifolia), the wild perennial cousin to salad rocket, likes to travel, particularly by train it seems, for I am forever finding it at railway stations. It waves its lemon-yellow flowers at passing travellers and hitches a lift farther north. There is enough around King's Cross in London to supply a supermarket, though one would be wise not to pick along the canals, as the aroma of pee is overwhelming on some patches – in fact, maybe that's why it grows so well. Pick ripe seed instead and sow it somewhere less trampled.

Unlike cultivated rocket, wall rocket is a perennial. The flavour is different, too: it has the spicy notes that salad rocket hints at, but they punch through with a powerful heat. By August, the leaves are so peppery they are best cooked for 30 seconds in boiling water, or a few chopped and added to a salad. I like the leaves torn on to a pizza just out of the oven as an alternative to chillies. The young leaves I like in warm salads with strong flavours – chorizo, parmesan or goat's cheese; it also goes well with oily fish.

Wall rocket hails from the Mediterranean, but has naturalised in the UK. As its name suggests, it haunts walls: I have seen cliff faces full of the stuff in southern Italy. A free-draining wall, a crack in the pavement and a patch of waste ground are all good homes.

Just because it likes wild places doesn't mean you shouldn't grow it at home. It's good for the low-maintenance garden, happy to look after itself. It self-seeds into the most improbable spots (in my garden along the path edges). If you can't find a wild plant to collect from, Seeds Of Italy sells the seed.

It's a tough plant, often producing leaves into winter, and is also one of the first to grow in spring, reaching 60cm. Plants grown in poor, very free-draining soil tend to be hotter to taste and sometimes a little tough. And if the soil is too nice, you may end up with a triffid that needs a regular haircut or it will flop.

The flowers are edible, too, and will attract beneficial insects. If you don't want the plants to spread, cut off the seedheads before they start marching across the garden.

One of the best uses of this plant if you have limited space is as a cut-and-come-again crop. You can get at least three cuts from a single sowing and the young leaves are more tender for salads. Sow from the end of the month, make another sowing before September is up and again in late spring. This should give you leaves into late autumn.