We've all heard that we should talk to our plants to make them grow better, but do plants talk to each other?

We've all heard that we should talk to our plants to make them grow better, but do plants talk to each other?

Plant scientists have known for many years that when a plant is attacked by insects, other plants of the same species in the group are somehow notified, and they start producing substances that repel the insect. Not only that, the plants put out substances that attract predators of the invading insect. The real question has been, "How do they do that?"

Researchers at the Institute of Biological and Environmental Sciences at the University of Aberdeen in Scotland think they may have discovered the answer, writes Jeff Cox in the magazine Horticulture. Their conclusions may surprise you.

The scientists weren't sure whether the signaling between plants was through gases the plants produced, through moisture in the soil or by some other means, so their research included ways to test those possibilities, plus testing some sort of communication at the root level.

Bingo! They discovered that it involved symbiotic mycorrhizal fungus in the soil. Symbiotic simply means two organisms depending on each other for their mutual benefit. Kind of a "you scratch my back, and I'll scratch yours" agreement. Mycorrhizal fungi are naturally in soil that is rich in organic matter. Most plants that grow in soil form mycorrhiza colonies, and in fact would not live without the symbiosis.

Mycorrhizal fungi live on the sweet sap produced by plant roots. To live up to their end of the symbiotic bargain, the fungus puts out long, very slender tentacles called hyphae, far into the soil to seek out and bring minerals to the plant, which it needs for growth.

The research team constructed ways to measure the plants' reaction to an invasive insect — in this case, aphids. They found that when the plants got the message that they were being attacked, they communicated that information to their fellow plants by way of the myccorhizal fungi.

This caused the plants to produce gases that both attracted parasitic wasps, which are natural predators of aphids and repelled the aphids. When the researchers blocked the roots or the hyphae of the mycorrhizae, these reactions did not occur. In fact, the isolated plants did not produce any "danger" signals.

So what does all this mean to the home gardener? Not only did the scientists show that the network of mycorrhizae signal danger to other plants, but they emphasized that the mycorrhizae thrive in soil that is rich in actively decaying organic matter.

While it would be wonderful if we could completely stop aphid invasions simply by using organic compost on our gardens, it seems to me that it certainly helps to keep lots of it in and on our soil. Any help we can give the mycorrhizae will be a good idea.

Coming up: Master Gardener Ronnie Budge will provide harvesting tips for our gardens, with emphasis on how to tell when the peak of ripeness has been reached. The class will be held from 7 to 9 p.m. on Tuesday, July 29, at the Southern Oregon Research and Extension Center, 569 Hanley Road in Central Point. The cost is $10. Call 541-776-7371 to sign up.

Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at diggit1225@gmail.com.