Friends and allies

EVERY month or two, another new scientific paper shares the next increment in our understanding of how plants communicate. I love that. Every day, quiet interactions occur, most beyond our gaze; some harmonious, others less so. The tip of this iceberg of interaction is companion planting, where we take advantage of one plant's qualities to benefit others. This can take many forms.

- Mark Diacono

Plants might offer their neighbours support: an established fruit tree makes an excellent scaffold for a climber, such as a kiwi or passion fruit. This works equally well with vegetables: in the classic Native American triplet of sweetcorn, climbing bean and squash, the sweetcorn provides the support for the climbing bean. This is only one part of the symbiosis: the bean feeds the sweetcorn and the squash by taking nitrogen from the air and releasing it through its root system, with the leaves of the squash paying the others back by suppressing weeds and retaining soil moisture.

Flowering plants can make excellent companions by bringing insects to the garden that will do the crucial job of pollination. Comfrey, lavender, ivy and thyme are only a few of those that are particularly effective in this regard. Added to this, there are many positive pairings where one plant attracts the predator to another's potential pest. Basil-a classic partner to tomatoes in the kitchen-can help maximise the quality of the tomato harvest by attracting aphids away from them. This self-sacrifice can occasionally risk the ultimate end: nasturtiums grown in proximity to brassicas appeal to cabbage white butterflies more than the precious greens, which gives you the opportunity to more easily deal with them as you see fitor to live with the (often extensive) damage to the nasturtiums.