Growing plants and being involved in horticulture since 1980 meant knowing the USDA’s plant hardiness zones so I could jabber to folks knowingly (Ha!) about plant choices for their personal habitat. To make things a little more confusing Sunset Magazine created their own hardiness and planting zones for the Western US. Jeez, Sunset! During my brief tenure at the University of Arizona I learned about C. Hart Merriam’s life zone system created in 1896 and I worked that into my plant blather for awhile. It did make me sound pretty smart. Then in 1994 along comes David Brown’s Biotic Communities…