My apple trees are well synchronized with each other, so I have bumper crops of all 4 trees in alternate years. Of course I want them to flower at the same time, so there is ample pollen for cross pollination of the different varieties. However, this year, the trees were unusually productive…
Is it just coincidence that these trees are so well synchronized or do they somehow communicate with each other about their status? A quick google search led me to a terrific article in Smithsonian magazine from March 2018 on this very question.
One way that trees, and plants in general, can communicate with each other is by way of the mutualistic fungi that entwine their combined roots.
The fungal strands search out and transport various nutrients that the plants need (nitrogen, calcium, phosphorus, magnesium, etc.) from the soil to the rootlets, and the trees pass photosynthesized sugars from the rootlets to the fungi in a very cooperative relationship. But it goes beyond just the interaction between plant and fungi.
Research by Suzanne Simard (in a very interesting TED talk) has shown that individual trees in the forest are connected in a dense underground web of overlapping and intermingling roots and fungal associations, and this web consists not only of a “mother tree” and its seedlings, but trees of all ages of other species as well. Through these connections trees exchange carbon and other nutrients, paying a small tax to the fungi along the way.
Not only are trees sharing resources in this busy underground network, but they are communicating with each other through secretion of plant hormones and volatile secondary compounds as well. For example, Giraffes that munch on the leaves of one acacia tree will stimulate the production of distasteful tannins not only in the other leaves of that tree, but in its acacia neighbors as well. In fact giraffes have learned to forage on the acacias that are downwind in a clump of trees to avoid this kind of response to the volatile chemicals released by the injured tree.
This kind of changes the way we look at forests, or even small patches of prairie, or garden plants, or shrubs growing together in our backyards. These plants aren’t as much competitors as they are collaborators, existing side by side, in a mutual quest for light, water, and nutrients. We could learn a lot from plants about cooperative existence!