They’re not Tesla Trees but they have some power.

Scientists have discovered that the bigleaf maple tree actually generates a very small current of electricity — in the millivolt range. But they also built a custom converter that stores it and produces 1.1 volts.

True, not a lot. But that is enough to run low-power sensors and such. And that alone is enough to trigger my imagination: how about low-power motion detectors for your yard? Or forests that generate a more sizable voltage, add water here, power the house over there… and I won’t even get into the far-fetched regions of my imagination.

The Huffington Post article

UPDATE: Apparently my geekiness got the better of me on my post title. Here explains the reference to Tesla Trees.