Growing Your Garden the Organic Way-Part I Organic Pest Control

Michele Obama uses the Three Sistesr method to plant crops in the white house garden with Native American children.
Michele Obama uses the Three Sisters method to plant crops in the White House garden with Native American children.

Organic gardening can loosely be defined as gardening by nature’s design.  This approach requires the gardener to only use products made from natural ingredients.  While this approach does work, there does exist another approach.  This approach utilizes Mother Nature’s plant relationships to the maximum and is referred to as companion planting.

Companion planting is described as the establishment of two or more plant species that are planted in close proximity to each other.  This closeness provides pest control, and higher yields while increasing the biodiversity of the garden space.

How this approach works is simple.  Plants that make good neighbors are planted together.  This good neighbor relationship has been tested since the beginning of time and is demonstrated through a Native American planting called the Three Sisters.

The Three Sisters companion planting demonstrates one of the basic principles behind the reason why companion plantings work.  This principle is referred to as the physical spatial interaction.  In this technique, sun-loving plants are planted first and in a Three Sisters planting that would mean corn.  Once corn is about 4 feet in height, beans are then planted.  The corn provides shade for the beans.  The beans, in turn, capture nitrogen from a symbiotic relationship with Rhizobium bacteria.  This relationship reduces the need for supplemental nitrogen.

Once the beans have germinated and have begun to climb up the corn stalks, the squash can be planted.  The large leaves of the squash plants help shade the soil and keep it moist.  The diversity of plantings, in turn, disorients the adult squash vine borer.  This means that the squash and beans are protected from this pest.  Also the prickly nature of some bean plants is known to prevent rodents from consuming the corn in the garden.

Another approach to organic gardening is to sacrifice one plant for the health and well being of another.  This is called trap cropping.  How trap cropping works is by planting one plant species next to another plant species but making one more attractive to the pest than the other.  An example of this is the relationship between collards and cabbage. A major pest for both of these crops is the diamond back moth.  This pest favors collards over cabbage.  Utilizing this love, the gardener can entice the diamond back moth away from the cabbage and onto the collards.  While the gardener will loose the collard crop, it will protect cabbage without the use of chemical pesticides.

A further approach that has been used for many years by the Amish culture is the use of biochemical pest suppression.  The basic principle behind this technique is the fact that plants produce chemicals from their roots, stems, leaves and even flowers.  These chemicals are released while the plant is alive and can also be harvested from dried plant material.

This particular technique is used to repel pests and control plant growth.  The Amish utilize the repelling nature of certain plants in their gardens.  This can be seen by the many African marigolds that are planted around and throughout their vegetable garden space.  These marigolds release a chemical called thiopene, which is a nematode repellent.

Another use for this technique comes from the production of rye.  This grain when mowed down and used as mulch inhibits the germination of seeds.  This includes both wanted and unwanted seeds.  To utilize this technique, the gardener must only use transplanted plants in the garden.

An additional technique that is used in organic gardening is through the creation of beneficial habitats or refugia.  This type of companion planting consists of creating a diverse environment that attracts beneficial insects and arthropods.  This includes both predatory and parasitic organisms. Predatory organisms that every garden needs include ladybird beetles, robber flies, mantids, hover flies, and lacewings.  Also, spiders and mites are a welcomed addition to this type of organic gardening.  Parasitic organisms include many different types flies and wasps.  These flies and wasps are crucial to the control of such pests as the Tomato Hornworm.

If you have a desire to try your hand at companion plantings remember to start small.  A good and simple combination to try beyond the Three Sisters is a combination of tomatoes and basil.   The strong aroma of basil is believed to deter the hummingbird moth away from the tomato plant.  This avoidance prevents this pest from laying eggs on the tomato plant and in turn prevents the tomato hornworm.  Also, this basil relationship improves the flavor of the growing tomato fruit.  Or color your garden with an old standby, the marigold.  Regardless of which approach you use, keep in mind that the reduction of chemical pesticides will make a better garden and future for generations to come.


Mindy McIntosh-Shetter has been an Agricultural Science educator, and is a horticulture and/or environmental blogger who earned a degree from Purdue University in Agriculture Education with a minor in biology, and natural resources. Presently she is finishing up her Masters in Environmental Education and Urban Planning for the University of Louisville while working on her own agriculture/environmental blog.

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