Companion planting is a practice whereby certain vegetables, herbs and flowers are planted in close proximity to each other because one of the plants is believed to have a beneficial effect on the other, or in some cases a mutually beneficial effect.
A few weeks ago, a reader of this blog contacted me requesting information about companion planting. I don't have first hand experience with companion planting but did a little research to help this reader.
Before you run off to re-plan your garden around companion planting principles, I need to tell you that I couldn't find any scientific evidence that companion planting works. I'm not saying it doesn't work, just that I couldn't find any experiments where companion planting was proven in a rigorously tested scientific experiment. However, there are many gardeners who swear by it and the companion planting pairings based on attracting beneficial insects and soil enhancement seem reasonable to me.
For those interested in in the subject, I'm posting a link to a very complete companion plant list created by Ute Bohnsack. Unfortunately, this chart doesn't specify the specific effect of one plant upon the other. However, here are some of the general reasons plants are said to benefit their companions:
- Pest Deterrence - certain plants can release chemicals from their roots or flowers that are said to repel insects and thereby provide protection to neighboring crops. For example, marigolds, mint, chrysanthemums and rue are said to do this and are often planted between crop rows to provide protection against pests such as nematodes, Japanese beetles and other nasties.
- Beneficial Insects - certain plants may attract beneficial insects that will either pollinate food crops or prey upon harmful insects that would eat the food crop. For example, planting bee balm to attract pollinating bees or corn flower to attract lady bugs. Companion planting advocates also try to develop habitats that allow toads, snakes and other insect predators to flourish.
- Soil Enhancement - for example, using nitrogen fixing legumes to enhance the soil that will benefit a subsequent crop.
- Spacial Interactions - tall, sun-loving plants are grown adjacent to shorter varieties that have partial sun, or lower heat requirements. Likewise, certain plants can be used as a wind-break to protect more delicate plants. Famously, corn and beans can be grown together with the beans using the corn stalks as natural trellises.
If you've tried companion planting, let me know if you think it works by posting a comment.
Photo: reverse side of the 2009 native American $1 coin issued by the U.S. Mint. The scens shows companion planting of the "three sisters" - corn, beans and squash.
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