Allelopathy is a chemical process that a plant uses to keep other plants from growing too close to it. Examples of plants that use allelopathy are black walnut trees, sunflowers, wormwoods, sagebrushes, and trees of heaven.
Allelopathic plants release chemicals that affect the growth of other plants. Ways that these chemicals are released include: :
- Volatilization – Allelopathic trees release a chemical in the form of a gas through stoma (small openings) in their leaves. Other plants absorb the toxic chemical and die.Leaching – Some plants store protective chemicals in the leaves they drop. When the leaves fall to the ground, they decompose, giving off chemicals that protect the plant.
Exudation – Some plants release defensive chemicals into the soil through their roots. Roots of nearby plants absorb these chemicals and are damaged.