Unfortunately anything the city does to make an area more desirable is inevitably followed by increased rents.
If you make everywhere nice, then you don't need to pay a premium to live somewhere nice.
Maybe you have to pay a miniscule amount more in property taxes.
You could just stop running trash & sewer service and let the city turn to garbage if you want lower rents. I don't think that's what people want. They want somewhere nice to live.
You can't have your cake and eat it, too.
On a city level, if - say - Chicagoland invested in all of its neighborhoods being beautiful instead of mainly just the wealthy areas near the lake - then you might have more people than expected migrate to the area and drive up rents everywhere, slightly.
But I'm skeptical...
As much as people like a nice neighborhood, you pick where you live (your metro) mostly based on jobs and your life - not trees.
You pick your individual neighborhood that metro based on a ton of factors. Trees could definitely influence that.
If trees are everywhere in that matro, then it's a non-factor.
There’s a reason the law that GP states, that all public investment is eventually baked into rents, is called the Henry George Theorem.
There’s no way around this, but with LVT at least society captures the returns on its investments instead of private landowners, which can then be reinvested e.g. in nicer public housing or public transit that allows a larger geographic area to participate in city life.