So in the last couple of decades we’ve discovered that many plants rely on networks of soil fungi to bring them critical trace nutrients. This is a symbiotic relationship: the fungal network can access these nutrients much better than plants can, and in return the plants provide the fungus with other stuff — particularly energy, in the form of glucose sugar, made from photosynthesis.

It turns out this relationship is particularly important for large, long-lived trees. That’s because trees spend years as seedlings, struggling in the shade of their bigger relatives. If they’re going to survive, they’ll need help.

The fungal network gives them that help. The fungus not only provides micronutrients, it actually can pump glucose into young seedlings, compensating for the sunlight that they can’t yet reach. This is no small thing, because the fungus can’t produce glucose for itself! Normally it trades nutrients to trees and takes glucose from them in repayment. So it’s reaching into its own stored reserves to keep the baby seedling alive.

Gosh that’s beautiful isn’t Nature great! Well… yes and no.

Because the fungus isn’t doing this selflessly. The nutrients and glucose aren’t a gift. They’re a loan, and the fungus expects to be repaid.

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