I think too much focus on the trees. To get to a trillion we need 125 trees per person on the planet. Removing those who are not in an area where tree planting is possible and cannot viably get to one, those who don't care, and those who simply cannot (children, disabled, etc) we are probably looking at tens of thousands of trees per person. I think at that point a tiered leaderboard would be more effective. Naming and photographing 10,000 trees is going to get old fast but getting to Forest Ninja level before your friends has some appeal to it.

Also there needs to be some system of logging (lol) which areas are ok to plant (avoid messing with earth's albedo, fire prone areas, for example) and among those which have not yet been planted. This will require and a way for users to check off what they've already covered and a collaboration with some organization who can say which areas are ok to plant and what types of trees will grow well there)

Furthermore there's needs to be an instructional aspect as to how to properly plant trees (seeds are a bad idea because they require regular follow up until they have sprouted). Saplings are a better bet which will require a list of places to get sapplings.

Ideally saplings will be free for users which will require coordination with governing bodies in every country that participates in order to subsidize the cost either at an individual level or directly to the suppliers. Either that or some kind of ad-incentive program for suppliers who are willing to donate.

It would be ideal if the suppliers rented tools as well and provided top soil and Schultz (growth mix).

This stuff has to come from somewhere. Either private equity or big brother. Should ask MacKenzie Bezos. She'd be down. Bono would be all over it. Bill and Melinda too. Maybe a live8 style benefit concert or something. Orr.. here we go, let people who can't go out and plant pay for the supplies for other people to do so. So you can have points for paying for trees. Points for planting them and triple bonus for doing both yourself because that's just awesome.

Or a mix of all the above. Pool the funds and then allocate them to suppliers when users indicate that they want to go to that location and get started. Really well suited for management by an app.

The app should also facilitate group efforts like matching groups of people in the same area with a nearby planting zone so they can rent a bus for a saturday and make a trip to somewhere a little less local.

I'm trying to think of ways to make this as frictionless as possible. Like i have an afternoon to kill and maybe some friends who would be down so I open the app. I need a map with available planting areas nearby and also sources for saplings. Do I have a car? A car with lots of space? Just a bike? Can I afford to fund this myself right now? Based on this are there any opportunities nearby? Maybe a notification based on those criteria if my location changes? Like maybe I'm on vacation and I need something to do or I'm driving somewhere and could stop for half an hour if the stars align.