The Debatable Benefits of Companion Planting
Complementary Plant Associations - are the Rewards Fact or Fiction?
Nov 8, 2009
Is there any evidence to support the claims that companion planting works? Unfortunately none that stands up to close scrutiny as yet, but investigations into its effectiveness are on-going. On its own, companion planting can't be relied upon to keep pests and diseases at bay, but it can be a useful weapon in the organic gardener's armoury.
The Problem With Growing Large Numbers of the Same Plant
Classification of plants as good or bad companions and advice on the proportions of each plant needed for the technique to work effectively is based on hearsay rather than proven scientific fact. However, what is absolutely certain is that mono-culture - the growing of large blocks of one particular type of plant, makes life easy for pests and diseases. In such situations they can multiply and spread rapidly, ravaging your plants before you can fill the sprayer with noxious chemicals.
The Benefits of Growing a Diverse Range of Plants
Growing a diverse range of plants in all parts of the garden has many benefits. Some plants like French Marigolds give off a strong scent which may keep whitefly out of the greenhouse. Unfortunately this only works when the marigolds are in flower.
The strong smell of onions discourages the carrot fly, but you need four times as many onions as carrots and the effect wears off once the onions start to form bulbs.
Mixed plantings can confuse pests. French beans growing with cabbages can reduce the incidence of cabbage aphid and cabbage root fly. Cabbage root flies taste plants with their feet before laying their eggs. If the plants they land on are French beans and therefore not to their liking they may fly off to pastures new.
Chives are useful in helping to keep fungal diseases at bay and for discouraging aphids on chrysanthemums, sunflowers and tomatoes.
Coriander is reputed to repel aphids, but if the coriander dries out it quickly becomes a target for aphids.
Annuals with simple, single flowers such as Californian poppies, pot marigolds and poached egg plants attract beneficial insects including lacewings and hoverflies which are predators of harmful insects like aphids.
Whether it is in the ornamental or the kitchen garden it pays to:-
- Grow a mixture of different plant species.
- Include some annuals with simple, single flowers.
- Encourage beneficial predators and parasites.
So What Can You Realistically Expect if You Adopt Companion Planting
By adopting a mix and match policy throughout your garden the plant combinations you create will certainly look more attractive and hopefully each plant will live in harmony with its neighbour. That being the case the healthy plants which result will be far less susceptible to attack from pests and diseases.
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