How Allelopathic Plants Work

Allelopathic plants secrete chemicals that kill off neighboring plants in order to increase their chances of survival. Some of these chemicals are only able to affect certain types of plants, while others can eradicate any plant in the vicinity. Once the soil has become contaminated, it can be almost impossible to wash out the harmful substances so other plants can live. Adding sand or other porous materials help aerate the soil and keeps allelopathic chemicals from building up. Controlled use of allelopathic plants can be an effective method of organic weed control.

Allelopathic plants: The effects on other plants

The chemicals used by allelopathic plants are as diverse as the plants themselves. Some plants use coumarins, while others use phenols, terpenoides, or juglone. Each of these chemicals has its own effects on the nearby plant life. Some chemicals can block the respiratory process of another plant, slowly suffocating it. Others inhibit the cell division processes that are vital for seed germination, preventing the plant from reproducing. Yet another type of allelopathic chemical can limit the victim plant's ability to absorb water and nutrients from the soil. Some allelopathic plants rely on physical measures to protect their resources instead of using chemicals. For example, salt cedar trees spread out an extensive root network that competes with neighboring plants for vital nutrients and water.

Allelopathic plants: How they work

Most allelopathic plants use the soil to distribute their harmful chemicals. As the soil is watered or subjected to rainfall, the moisture spreads the chemicals throughout the area. The type of soil can limit the spread of these chemicals or allow it to build up and become even more dangerous. Soils that do not drain well, like clay, allow the chemicals to build up. Over time, the clay soil may become completely unusable for any other plants besides the allelopathic plant that contaminated the area. On the other hand, a porous material like sand drains quickly, washing out the harmful chemicals along with the water.

Allelopathic plants: Beneficial uses

While allelopathic plants can be a nuisance when growing unchecked, they are helpful when used in a controlled manner. They can be used to control weeds and pests naturally, which reduces the amount of chemicals in the garden. The chemicals that cause the allelopathic effects are being studied in an effort to produce commercial pesticides and weed killers. One possible use for allelopathic chemicals is as a growth retardant for trees that grow under power lines. This could save utility companies a significant amount of money on tree pruning costs each year.