I've given this a few minutes of thought. Basically, the situation is that some bacteria take nitrogen from the atmosphere and then spew out ammonia and related compounds, which are taken up by the roots of the symbiotic plants. I would call this "fertilization" (in the agricultural sense).

But then it becomes ambiguous whether you're talking about fertilising the tree, or the tree fertilising something else. Perhaps self fertilising? But that sounds like reproduction.

And that's assuming we're living in a world where you can petition the World English Language Governing Body to make the necessary changes to the language.

But for better or worse that body doesn't exist so we are stuck with what we've got, and at the moment people talk about nitrogen fixing plants, so if you want to communicate with people, you need to use those terms.

That isn't clickbait, that's just making sure a headline doesn't turn into an off topic essay.

> whether you're talking about fertilising the tree, or the tree fertilising something else.

Of course, I would say that the tree is being fertilized or receiving fertilization, not that it's fertilizing.

The effect of the bacteria can be replaced by animal waste, decaying biological matter, or the application of a commercial fertilizer.

> self fertilising

That would be false and absurd; it means that the plant is decomposing in order to feed itself.

> and at the moment people talk about nitrogen-fixing plants.

Not people who can pass a fifth grade science exam. Nothing to do with English usage. "Nitrogen-fixing credit card" is grammatical English.