An unwanted dinner guest: How do you grow salad leaves that won't come complete with creepy crawlies?

This is a very enjoyable meal, except for one thing: there's a curled green caterpillar in the middle of the plate. He's not even a small caterpillar. He's a long, fairly fat boy with a healthy yet unappetising wiggle to him, despite his stay in the salad. The waitress is surprisingly unsurprised: "The leaves are organic," she tells me, as if that explains why they didn't get a proper wash.

But she's right about one thing: the greenest salad in the land always comes complete with the possibility of a bush-tucker trial. You'd have thought we might have got our heads round the idea of some extra protein along with our chemical- free rocket as some sort of modern gastro treat, but actually I have yet to find anyone who relishes the idea of downing tiny invertebrates. As it turns out, when it comes to salad, we are all a little bit Jainist.

So, how to balance the idea of a green (side) salad, with the ideal of a green (eco) salad? Luckily, there are ways of greenly reducing the pest count without upping the pesticides. First, you need a siege mentality, and consider your enemy. Think about barriers. One of the best tips for salad-growers is to appropriate some of those polystyrene fish boxes you'll see out the back of fish-and-chip shops. No need for theft: you can just ask. Recycled fish boxes make great growing trays for salad, keeping little roots six inches up and away from general marauders.

If you grow in the right sort of container, it can be set in a moat of water that will satisfy even the most fastidious, ensuring that only the bravest of critters make it across. Or, buy copper tape and use it as edging to fence off your slug-free area. I would highly recommend this, and have had several crops saved by it. (£6.95 for a four-metre roll, harrodhorticultural.com).

Now you've secured your perimeter, order some nematodes. September is still warm enough to use a dose of nematodes, as long as you get straight on the case and use them as soon as they arrive. Nemaslug nematodes come with copious instruction, and will kill all molluscs within the bounded area. You can do quite a large patch with a single packet (£9.95 covers 40 square metres, the size of a small town garden).

However, back to caterpillar watch, and we still need to prevent moths flying in and laying eggs. To dissuade them from that sort of antisocial behaviour, the crop must be covered in some way. Harrod sells substantial cloches and tunnels that let light through, but provide a physical barrier to moths and butterflies. They will also let you grow for longer, giving you greens well into the shorter autumn days. And, of course, finally (unlike our restaurant salad-makers): always wash carefully.

For more pest information and details of all these products, download the encyclopaedic "Little Book of Pests" from harrodhorticultural.com

Autumnal acquisitions

Rocket

Now is the perfect time to sow rocket, which suffers during warmer weather. "The Best Autumn and Winter Salad" from Sarah Raven (sarahraven.com) is £10.50 for six varieties, including rocket, corn salad and Mizuna

Pea shoots

These are a delicious addition to a bowl of green leaves, and easily started from normal pea seed. They can be sown very close together if you harvest early – two or three per yoghurt pot. A lovely sweet variety is Douce Provence, £1.65 a packet from marshalls-seeds.co.uk

Microleaves

For the terminally fussy, these can be grown in seed trays on windowsills. Buy the microleaf grow tray from Marshalls, £4.95, and a seed collection including broccoli and red radish for £6.95 (marshalls-seeds.co.uk)