TOPIC: Free Apps?

I was wondering if there is anyone that could help me find an app for my phone that would be the best in helping me learn about native herbal plants in the field. Does anyone know which is the best free app to use?

I, too, would love to hear an answer to this. I'm very eager to learn more about plants and herbs. I'd also be willing to pay a small price if someone thinks it's well worth the money.