Communal Beat

Companion Plants and Protective Allies

Companion Plants and Protective Allies
By: Barbara Odegard


Using plants as companions and protective allies is the knowledge of which particular plants thrive in the presence of which species and which ones do poorly when in the presence of others.

The quality of food and flowers is improved.  Pests and disease are reduced. These relationships have a positive effect on the micro life of the soil. Through observation and use we begin to understand that all plants are specialists in some way

The observation of these relationships deepens our understanding of nature’s abilities to enhance and protect itself.  It helps us to become more sensitive and aware of the incredible ways in which we can help nurture the nature in our own gardens.

These are chemical and physical influences that are exerting their effects on their surroundings.  These substances control the metabolism of the plants and thereby increase or decrease the vigour of the plants. This knowledge applied correctly will help increase yields and lower susceptibility to disease and pests .

Companion planting, or intercropping, allows us to take advantage of certain chemical interactions between plants. These interactions can be used to encourage plant growth and health to be mutually beneficial. Every plant releases different chemical compounds, either above ground through its leaves, or below ground from its roots. These chemicals attract or repel insects and either aid or discourage their growth and reproduction.

Allelopathy“Is the repression or destruction of plants from the effect of certain toxic chemical substances produced and released by other, nearby plants.”Allelopathy must be clearly distinguished from competition. In competition the plant reduces or removes minerals, water, space, gas exchange and light. Competition creates the environment for the plant to take action and allelopathy is the result of those actions.  Competition and allelopathy act simultaneously. Examples of this are some of the non-native,  introduced weed species which threaten and out-compete native species


Below ground, plant roots release compounds into the soil affecting plants in a positive or negative manner. Plants respond with health or disease. Compounds emitted from plant roots will either attract or repel underground insects. A good portion of herbal medicines are made from plant roots because of these factors. The roots concentrate these compounds which makes them so powerful. Above ground, plant foliage also gives off chemical scents – alkaloids, sulfides, and phenol compounds which repel or attract insects, or act as a natural fungicide.

Chemicals released by a plant’s foliage are increased by watering, heat, and stress. Each plant has a different molecular vibration, or wave length. Insects use these vibrations to determine the location of the plants growing in your garden. Using companion planting, insects are not able to easily find and settle into an area to eat, reproduce, or hide.

It is more than evident that plants form relationships and adapt to their environments through constant communication. As plants grow and mature they develop their personalities, essences and aromas. Many of our more wild, weedy and native species become specialists in the plant community aiding and assisting our more cultivated species.

This field of study is yet in its infancy.  As we begin to understand the complexities of plants we reveal a language we are slowly able to interpret. It is obvious that plants have much to teach us and we have much to learn.

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