I’ve talked about the USDA Hardiness Zone map before (Nov 2018). It is a great tool to help gardeners decide what plants can be put in their landscape. The map was recently updated by the USDA and made public in November of 2023. Portions of Douglas and Sarpy counties in Nebraska along with many southeast and south-central counties and small pockets in Keith, Hamilton, Hayes, Washington counties along Pottawattamie, Mills, and Fremont counties in Iowa have been shifted to zone 6a.
What does this mean?
This means our average extreme minimum temperature shifted by 5°F to -10° to -5°F. However, the map does not tell us about weather anomalies, sometimes extreme, and we’ve had some the past few winters. In December of 2022 Omaha recorded a low of -14°F on the 22nd and in February of 2021 a low of -22°F on the 16th. The map does not tell us about perception, soil conditions, microclimates, plant health, and a slew of other factors that all play a part in plant survivability.
What should you do?
We need to be diligent when purchasing plants. If zone 6a plants start to make their appearance in garden centers, we should proceed with caution. We should learn what we can about those plants before putting them in our landscape. Just because they might be able to survive our winters doesn’t mean they can survive our growing conditions.
Checkout the evolution of the map below.