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HomeTopics...Gardening TipsAllelopathy
Allelopathy: How Plant Chemicals Affect Your GardenAllelopathy is a term used to describe the effect that chemicals in garden plants have on other plants. Many plants emit agents called allelochemicals, and these chemicals can harm nearby plant life.
For instance, the leaves of certain trees contain toxic acids. When falling leaves make contact with adjacent trees or plants, this acid can inhibit the growth of those neighbors. In effect, allelopathy can be likened to a war that plants wage on one another. As Charles Darwin hypothesized, the conflict is about survival of the fittest. Allelopathy is how plants struggle against each other for soil nutrients and sunlight—and some of them are armed for combat.
Put Allelopathy to Good UseAllelopathy can play a major part in the ecology of your garden by altering the structure of a plant community. Allelochemicals can have a strong affect on plant domination, diversity and productivity. Once it's understood, allelopathy can be used by gardeners and farmers to achieve greater productivity and better plant health.
The applications of allelopathy are diverse. For instance, allelopathy can be used to suppress the growth of garden weeds or to limit the creep of plants that can take over lawns or destroy wooden fences.
The Black Walnut ExampleThe black walnut plant is a good example of allelopathy in action. Scientists who have studied this plant have isolated juglone, a toxic compound that's found in black walnut. The plant manufactures juglone through a series of elaborate chemical reactions, and it stores the compound in its leaves, bark, wood and roots.
When it penetrates nearby soil, juglone can inhibit the growth of azaleas, rhododendron, potatoes, tomatoes and other plants. In fact, some of these plants die if their root zones are penetrated thoroughly. On the other hand, some plants like melons, beans and carrots, that tolerate juglone without a problem. And the growth of others, like Kentucky bluegrass, is stimulated by juglone.
Allelochemicals and the SoilEven when a plant is uprooted and removed from a garden, it's allelochemicals can still permeate the ground in which it had been growing. That soil can continue to have an affect on surrounding plants.
Allelochemicals are especially persistent in soil that drains poorly, such as soil with a heavy concentration of clay. Gardeners can improve the soil and eliminate the lingering allelopathic affects by enriching it with organic material. Invest a few hours in reading up on plant chemical interactions. Experienced gardeners and the experts at your local nursery are often delighted to share their knowledge with avid gardeners
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