companion planting

Traditional Companion Planting

Companion planting can be described as the establishment of two or more plant species in close proximity so that some cultural benefit (pest control, higher yield, etc.) is derived. The concept embraces a number of strategies that increase the biodiversity of agroecosystems.

Generally, companion planting is thought of as a small-scale gardening practice. However, in this discussion the term is applied in its broadest sense to include applications to commercial horticultural and agronomic crops. ATTRA has another publication, Intercropping Principles and Production Practices, that provides additional information on larger-scale applications.

While companion planting has a long history, the mechanisms of beneficial plant interaction have not always been well understood. Traditional recommendations (see summary chart provided as Table 1) used by gardeners have evolved from an interesting combination of historical observation, horticultural science, and a few unconventional sources. For example, some of the recommendations for companion planting, made around the middle of this century, were based on the results of sensitive crystallization tests (1).

Originally developed by Dr. Ehrenfried Pfeiffer, sensitive crystallization testing entails the mixing of plant extracts with select salt reagents like sodium sulfate or copper chloride. The resulting solution is placed in a controlled environment chamber and allowed to evaporate slowly. The process results in a precipitate that often takes on beautiful geometric forms and patterns. The characteristics of the pattern are studied and interpreted to establish whether the plants are likely to interact well with each other (1). Sensitive crystallization appeals to practitioners of Biodynamics™ (BD) and others who take a more metaphysical approach to nature. Conventional science is much more skeptical of this process as a means to evaluate plant associations.