Taking children to natural areas outdoors is a great thing to do; however, you may not always be able to access these locations. Consider what natural materials are accessible from your current location. Natural materials do not have to be removed from their natural environments, or these could be retrieved from the ground (i.e. the natural materials that have fallen from a tree, bush or plant, and have not be forcibly removed).
With these concepts and questions in mind, develop your natural material play philosophy, including what you will communicate to children about how you view the outdoors, nature, and natural materials.