The USDA just released a new plant hardiness zone map. Plant hardiness zones are listed on plant tags to communicate the regions in which plant should survive without extra winter protection.
Many will find their zone has changed by a half – mine went from zone 6a to zone 6b, slightly warmer.
Will this alter how I garden or what I plant? No. The map does not take elevation and cover-, slope-, or hardscape-related issues into consideration. Only eyes and experience can do this. I know my property. Plants, shrubs and trees listed as borderline in zone 6 may not survive tough winters without coddling (this means extra winter protection and extra work). If I must have a plant that is borderline in zone 6, I do so with the full knowledge that coddling/extra work will be part of my regular gardening routine.
This is exactly what the USDA recommends on their Maps & Gardening page.
The new map considers 30 years of climate data – a longer period than the 15 or so years previously used and used in other plant hardiness zone maps. More about how the new zone map was created is on the USDA’s What’s New page.
The new map is more interactive than previously. After choosing to view by State, Region, or Nationally, and choosing a size (try Standard then move on to larger versions), you can preview, open or save your map choice. If you start here, and type in your zip code your zone will pop up under your zip. Or, for a closer-up view, click on the Interactive Map tab and type your zip code. In the interactive map you can activate a satellite image that shows up under the zone colors. If you increase the transparency of the zone color layer it’s easier to locate your property on the satellite image.
This is particularly useful when trying to determine planting zones in areas near zone borders. For instance, my property, listed as zone 6a in the older USDA map and in the Arbor Day Hardiness Zone Map, is now located very close to the edge of zone 6a in south-central Connecticut but is newly listed in zone 6b.
Follow the various links above and play with the features, but don’t forget that we still must garden thoughtfully. Hardiness zones are guides. Gardeners with the time, experience and where-with-all to push a hardiness zone – say by planting a zone 7 perennial in a zone 6 garden – can be quite successful. Gardeners looking for less maintenance and fuss should stick to their zone or acknowledge that a perennial listed hardy in a warmer zone should be planted as an annual or overwintered with protection.