Northern & Central Midwest
Wild Ones is the ultimate place to go for information on native plants and naturalistic plantings. Its mission statement says it all: "Wild Ones promotes environmentally sound landscaping practices to preserve biodiversity through the preservation, restoration, and establishment of native plant communities. " There is almost more information than anyone could process, but it is a wonderful place to find the answers to your questions.
In Naturalistic Gardening (Sasquatch Books, 2002), author Ann Lovejoy's opening statement, "Gardening is by definition interference with nature," tells you where she is heading from the start. She defines and instructs the gardener to design a garden which doesn't necessarily copy nature, but instead "mimics" nature. She encourages us to look at nature's layers and natural forms when designing the garden. She received an American Horticulture Society Writing Award for this book, which has a delightful, informal style that will keep you reading and planning long after your garden is finished.