What are your thoughts on the new USDA hardiness zone changes?

[Richard]

@a_Vivaldi

I think one salient point is that there isn’t necessarily all that much wrong with the USDA zones.

Provided they are used as intended: “Cold hardiness zones”.

In no way are they “climate zones”.

@swincher

the whole point of that system is to answer “what can I grow here?”

That’s a misunderstanding on your part.

[swincher]

@Richard

That’s a misunderstanding on your part

No, I understand that it is not very good at answering that question, but certainly it is the primary reason the USDA created the concept of hardiness zones. To help people answer the question “what can I grow here?”

[Richard]

@swincher

certainly it is the primary reason the USDA created the concept of hardiness zones

I disagree. Certainly many sellers, journalists, and so-called master gardeners have presented it that way.

For more information, I recommend the USDA annual report which discusses the introduction of the metric.

[swincher]

@Richard

I recommend the USDA annual report which discusses the introduction of the metric

Ok, well what about the very first sentence in the official description of the USDA hardiness zone map?

The USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which perennial plants are most likely to thrive at a location.

From here:
https://planthardiness.ars.usda.gov/home

I obviously agree that it’s a flawed “standard” for that task since it is too one-dimensional, but are you really going to argue that the USDA is lying about the purpose of their map?

[Richard]

@swincher

are you really going to argue that the USDA is lying about the purpose of their map?

At best it is a misleading statement. Note that “hardiness” and “thrive” are at significant distance on a semantic map.

[LarryGene]

The USDA hardiness zones are 30-year calculations that can become outdated by 9 years due to their once-per-decade dataset updates.

My various Eucryphia shrubs and trees thrived for 25 years. It is sad to see them decline after two consecutive years of winter teens, but overall, it worked for me.

[Richard]

@alanmercieca

It appears that sunset magazine used to have a sunset zone map for all of the USA

Sunset magazine was privately held until it’s sale to Time Warner in 1990. There were plans to develop a nationwide climate map to build value in the Time Warner portfolio. But after a while it became clear that TW’s business model wasn’t a good match for this endeavor. On top of it, magazine sales shrank dramatically with the advent of Web browsers. TW sold Sunset magazine to a private equity firm in 2017.

Here are the maps presently supported by Sunset:

Climate Zones | Sunset Plant Collection

[scottmartin49]

We went from 4b to 5; completely in agreement with my own observations of the last 20+ years.