Plants to help one another
makes the most of the beneficial effects that plants can have on each
other and on pests. Aromatic compounds in roots, leaves and flowers or
secretions from parts of some plants can act as effective deterrents to
many common pests.
As well as protecting against pests, companion
planting results in fewer weeds as deep-rooting plants grow alongside
shallow-rooting plants, compact plants with broad leaves alongside
thin-leafed plants. This means there is less room for weeds to take
Growing carrots with leeks, garlic or onions is a tried and
tested combination, with the companions protecting each other in turn
against carrot fly and onion fly.
When planted between
strawberries and vegetables, onions and garlic also help to protect
against fungal infections. Strong-smelling winter savory protects dwarf
beans against blackfly, whereas nasturtiums help to protect tomatoes and
fruit trees from greenfly and the woolly apple aphid.
When planted among vegetables, secretions from the roots of pot marigolds (Calendula officinalis) and French marigolds (Tagetes patula) help to deter eelworms.
celery between cabbage plants drives away cabbage white butterflies, so
that they look elsewhere for a place to lay their eggs. And the
aromatic leaves of sage also deter cabbage white butterfly as well as
being offputting to snails and ants.
Often, a pest problem in a garden can be averted before it actually becomes a problem.