USDA hardiness zones Q. What do you say is our planting zone?  I got a Plant Smart Sensor for Christmas and it says we are a 7B which is way lower than I always read.  Just because a website says a tree or plant will be ok for a certain zone doesn’t mean it is necessarily right? A. I use both the USDA and Sunset’s planting zones for our area. Because we have various microclimates in landscapes I will normally include a couple of climate zones colder for very exposed microclimates and a couple of climate zones hotter for protected areas with lots of exposure to sun in the winter time and wind protection. Start with winter time lows reaching 10F and add zones that are just at freezing (32F) to cover our microclimates in backyards. Yes, they will vary that much. USDA Hardiness Zones http://www.usna.usda.gov/Hardzone/hzm-sw1.html             I like Sunset’s zones but find them a little bit too narrow at times and too restrictive. That is the reason Sunset went ahead in developing their own which they did a fabulous job doing. On the other hand, the USDA zones are too broad. Very little in this world is perfect so I use these fudge factors I mentioned to “fudge in” the microclimates. Mojave Desert Las Vegas and Arizona Mojave Desert Las Vegas and California             Frequently, the selection of a plant and whether it will work or not, depends on several things: the microclimate, where you plant it in the yard, how you modify the soil and irrigate it.