The trench has beans, onions and sunflowers

The magic and mystery of companion planting have intrigued and fascinated humans for centuries, yet it is a part of the gardening world that hasn't been sufficiently researched.

This picture is the trench adjoining the tomatoes. The near side is a bunch of carrots. To its detriment, these carrots may aid the tomatoes. Far behind in this same trench, I've a patch of spring onions. I've not invested the time to research the onion-carrot companionship. But that shouldn't deter me from experimenting. In part, this is to scatter onion plants throughout the garden - onion maggots travel from plant to plant when set in a row.

Extending this principle, here's the tip for the day: The active principle of tomato leaves is solanine, a volatile alkaloid that at one time was used as an agricultural insecticide. You can create your own insect-repellent spray for roses by making a solution of tomato leaves in your vegetable juicer—add 4 or 5 pints of water and 1 tablespoon of cornstarch. Strain and spray on roses where it is not convenient to plant tomatoes as companions. Keep any unused spray refrigerated.