Ask HN: Where to get data for a Web/iPhone app idea?

So I want to make an app that tells you all poisonous plants that you could potentially encounter in your location, with pictures, etc.

Is there any way to get A.) a list of poisonous plants across the world. and B.) The geographic coordinates of the plants' ranges? I'd be happy even with just a shaded map, and figuring out the boundaries from that.

(Poisonous to touch would be fine, I probably wouldn't add poisonous to eat since that's probably a lot of plants.)