Hello Global Warming. I've moved from a 5b to 6a? Jeeze this getting old thing makes all the numbers go up! The USDA has released the 2023 revised Zone Hardiness Map based on the thirty year average of lowest annual winter temperatures. Historically we have been in zone 5. If I zoomed in real close on our neighborhood, we were a 5b and some properties on my side of town were in zone 4. This is probably due to elevation above sea level. You get cold pockets and warm spots.
Gardeners know that you have to take this hardiness zone thing with a grain of salt. Many places in the country have recently experienced winter storms that kill off a lot of established plants. In your own garden you might find microclimates near buildings or behind wind breaks where plants would do better in a severe winter. If you are planting perennials or evergreens in containers, it is wise to plant for two zones colder because the roots are more likely to freeze when they are in a container as opposed to in the ground. When choosing perennials I would compare hardiness zones of the cultivars I was considering and favor those which were hardy to a zone 4 or even 3, especially when planting evergreen or winter blooming plants such as Primrose, Heuchera or Hellebores.
Well the rules of the game have changed again. Over time, this will certainly shift what sort of plants we are seeing sold in the local garden centers. Just because the USDA says so, does not mean I will shift my gardening habits just yet. But it may mean that I will try some plants that I've shied away from in the past.