Allelopathy

Posted by Robert Dailey Jan 19, 2008

Allelopathy (from the Greek, allelon, meaning another and pathos, which means to suffer) is a way some plants deal with competition.

Allelopathic plants release chemical substances which literally make other plants suffer. Some of these allelopathic plants store toxins in their leaves. When the leaves fall to the ground, the toxins are released. These toxins leach through the soil and are taken up by other nearby plants.

Alternately, allelopathic plants can release chemicals through their roots. These toxins travel thr;ough the soil where they can be absorbed by the roots of other plants.

Some allelopathic plants use gas warfare by releasing allelochemicals through small pores in their leaves and gassing nearby species.

Plants like black walnut (Juglans nigra) have allelopathic chemicals in their leaves, bark and roots. This chemical (called juglone) is particularly toxic to members of the Solanacea family, which includes deadly nightshade, potatoes and tomatoes. It is also toxic to azaleas, rhododendrons, mountain laurel, blackberries and blueberries.

Pecans and hickories are relatives of the black walnut and also have fairly high levels of juglone.

Of course, black walnut is only one plant that is allelopathic. There are many others.

Other allelopathic plants include sagebrush (Artemesia grandiflora), red cedar, some species of pine and eucalyptus, some clovers, fescues and sunflowers to name a few.