The USDA has updated the Hardiness Zone map.

https://www.ars.usda.gov/news-events/ne ... -zone-map/

Some areas of the US have shifted zones more than others. About 1/2 the country shifted to the next warmer half zone.

Sure enough, compared to the 2012 map, I have gone from Zone 5a to zone 5b. But this has no effect for me as I mostly only grow annuals anyway.

I just thought it was interesting...

I can only say what the wife has told me and that is hardiness for perennials was the same for us they have always said we were a 5B but you need to consider your microclimate so we have always gone with 4A as we face east-west.

Even when we lived on top of Conifer Mountain at 9800ft they did everything by zip code.

Basically, she told me with the exception of places toward Colorado Springs and Pueblo most things in the state were left as they were.

She has more than once told me zones are only for perennials nothing else.

I hope this helps she met with her Master Gardener Group a few days ago.

For us gardeners that's exactly right. (Scientists, insurance companies, etc. use the map for other reasons).

It is simply a 30 year average of the lowest annual temperatures for specific locations.
For a summer vegetable gardener it makes no difference to me. However, when selecting perennials (e.g., asparagus, rhubarb, strawberries) and things like garlic then you need to know your zone in order to select the right variety.

Yes, micro climates make a difference. That's why each generation of the map shows more and more detail. If you look at older zone maps like from the 1960s the zones are bigger swatches and this area of Colorado is clearly indicated as zone 4.

This newest map has far more detail (and is not by zip codes). However, you can put your zip code in their online calculator and it will generate a zone, which may or may not be the zone at your property. As for micro climates, you have to look at the map much more closely.

However, what I find interesting is how each revision of the map shows the way the zones are moving north as our climate warms.

She has a link to a person in Denver who reviewed things prior to going public I will ask her tomorrow he is a Master Gardener in Parker.

I think he shared with her group the differences but I am not sure about this.