Expert: Frank and Vicky Giannangelo - 12/2/2008

Question
Using simple wording and terms could you please explain why inter-relationships between living organisms are important in organic horticulture?

Answer
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 in a symbiotic manner. Every plant releases different chemical agents, 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.

Below ground, plant roots release amino acids, vitamins, sugars, tannins, alkaloids, phosphatides, and glucosides into the soil, affecting plants either positively or negatively, resulting in plant health, or disease. Chemicals emitted from plant roots will either attract or repel underground insects. Many herbal medicines are made from plant roots because of these factors.

Above ground, plant foliage also gives off chemical scents - alkaloids, sulfides, and phenolic compounds - which repel or attract insects, or act as a natural fungicide. Chemicals released by a plants 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. Chemical interactions also affect plants growing in close proximity, either promoting or retarding their growth, and health, above and below ground.

A garden planted with single rows uses more soil area and resources, is more difficult to mulch, the soil dries out faster and produces more weeds, and becomes quickly compacted from walking and jumping between rows. Planting crops closely together in wide rows, takes advantage of the physical and chemical characteristics of each plant. Planting crops close together for the highest yield of each plant will benefit each plant, if planted in symbiotic relationship.

Intensive intercropping, along with companion planting, will provide the maximum amount of food production, and will reduce your garden size, water and nutrient requirements, and allow you to grow the healthiest plants.