Generate a full detail guide that simply explains USDA Plant Hardiness Zones. The guide must be educational for beginners. It should include: 1. A clear definition of what a hardiness zone is (based on average minimum winter temperature). 2. A guide on how to find your specific zone. 3. A detailed example using Zone 7b (the zone for Union City, Tennessee), explaining what it means for plant selection. 4. A section on other factors to consider besides your zone, like microclimates and soil type. Please include a supportive disclaimer.