[yasth]

Honestly they don't seem to be that close to cracking it, like at all.

They may be using camera phone images, but they are well framed images of very distinctive features. Trying to recognize a literal tree in a forest is going to be far harder, and recognizing a tree based on a dead leaf (as a photo towards the bottom suggests) can be very very tricky. Also I have to admit to being concerned that adding "any known plant" won't kill accuracy. The more classification endpoints the less likely you are to get a decent result, and already you have to deal with far greater scale differences than are usual (basically it would be like identifying the breed of dog from anything from a full picture to a photo of a single claw).