Answer: The zones on Monrovia's website are USDA zones. While Sunset's zones are useful for the west coast, there is nothing comparable for the rest of the country. So, the zones are USDA. Once you find a plant you like, you can look it up in Sunset Western Garden Book, or you can visit National Gardening (www.garden.org) and find information on both USDA and Sunset zones. Best wishes with your garden!
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