There is no required reading in gardening. Lots of people learn all they need to know by watching others and asking questions, by trial and error, or plain good luck.
Garden Perennials for the Coastal South Barbara Sullivan, UNC Press, Chapel Hill, NC, 2003. Vital information not available anywhere else in such comprehensive form.
PlanBee: everything you ever wanted to know about the hardest working creatures on the planet, Susan Brackney, Perigee/Penguin Group, New York, NY, paperback 2010. Caution: when Susan gets through with you, you’ll be itching to get hives for your own backyard. Brilliant.
Teaming with Microbes Revised Edition, Jeff Lowenfels and Wayne Lewis, Timber Press, 2010. Get serious about soil organics and develop religious fervor for compost tea. They’ll make you smarter and more serious about gardening.
Armitage’s Vines and Climbers: a gardener’s guide to the best vertical plants, Allan Armitage, Timber Press, 2010. Not your average encyclopedia of plants because of the professor’s straightforward, yet fun style.
What’s Wrong With My Plant? and how do I fix it? A Visual Guide to Easy Diagnosis and Organic Remedies, David Deardorff and Kathryn Wadsworth, Timber Press, 2010. The title says it all.
Gardening with Native Plants of the South, Sally Wasowski with Andy Wasowski, Taylor Trade Publishing, paperback 2010. A classic returns to deliver insightful guidance into using native plants in modern landscapes with great results.