Most of the botanical pieces I make come from species found here in New York, but I recently made a twig wedding ring in 14k palladium white gold for a customer who sent me branches from a southern live oak. These oak trees are very different from the ones here. Their leaves stay green in the winter, so they're a type of evergreen, and the twigs and leaves are very different in shape. And they grow huge, and often have moss hanging off of them in the south. My customer was nice enough to let me use the mold of her twig to make more pieces. Right now I have them cast in sterling silver, but can make them in other metals.
Here's the 14k palladium white gold version: