Call 311.

Can you access it? If so, just do it. Just start.

I lived on a block that had a tree with dirt around it where everyone would throw trash and dogs would urinate/defecate. I cleaned it up and brought in dirt, put up a fence and planted. It was a struggle to keep it going, clean, etc. But whenever someone would see me working out there and stop to tell me thanks and how beautiful it was, it was all worth it. I moved off the block and visited 2 years later and someone had created something even bigger and better than I had. But it took me to start it.

Here's a link to an org called Green Guerillas: www.greenguerillas.org/ I bet they could give you some great advice too.

you might want to contact Trust for Public Land - www.tpl.org. They are a non-profit that do things like this in NYC.

Thanks for your suggestions, I will check out the links! I would like to just "start it" but it's a kinda big plot, I will put some thought into how to set aside a little space to protect some flowers. I will probably have to start small until I recruit some helpers. I do think, like you said X!ne, that it makes such a difference to have a small square of beauty. Everyone appreciates it and the beauty can spread and multiply.