The cold hard facts

This may be common knowledge, but it has dawned on me that deciduous trees are more susceptible to extreme cold temps, while evergreens are more vulnerable to unusually persistent cold temps, like we had this past winter. The absolute minimum this past winter in Eau Claire was -25F, which is certainly cold, but no where near record cold temps. The problem is that we had a very high number of days where the low ranged from -10 to -20, and the highs were often from 0 to 15. I'm still reluctant to declare that all of my deciduous woody plants have survived, but it's looking more promising each day. Unfortuately, the same cannot be said for evergreens. However, deciduous conifers, like Pseudolarix and Metasequoia 'Ogon', which are considered very marginal here, have both survived. Again, if I am merely stating the obvious, never mind. ;)

That's a cold hard opinion.

Yours isn't an obvious statement, and at the risk of ruffling Cheesehead feathers - I'll say that it crosses the border into incorrect.

Let's start with what plants grow where, and a few definitions. You use the term evergreens mostly to mean conifers, and that's understandable for northern Wisconsin experience - which is where you should alter your terms.

Plants which retain foliage more than one growing season are often termed evergreens, but include needled types (mostly conifers) AND broadleafed types like Southern Magnolia, American Holly, et al.

As one proceeds northward in latitude and upward in altitude, I think you will find that the woody plant community generally reduces to conifers. This conflicts with your suggestion that tthis category of evergreens performs poorly during unusually persistent cold temperatures. I believe that - appropriately sited - that conifers are supremely adapted to just these kinds of conditions.

Your observations are better applied to the species you've mentioned that are planted outside their comfort zone - for which the variables you've suggested are just some of what have had effects upon their growing performance, and with which I do not disagree.

Now that my frigid feathers are unruffled, I can respond to your reply. First, to state the obvious, I was using the term evergreen to mean conifers. I didn't mention broad-leaved evergreen trees like American Holly and Southern Magnolia since they do not exist here and I assumed most if not all readers would know that. Perhaps I was wrong in making that assumption.

Second, I wouldn't argue that conifers in general are quite adapted to cold conditions. My point is that non-deciduous conifers "...are more vulnerable to unusually persistent cold temps" vs. deciduous trees, including deciduous conifers, when planted outside their normal range. I should add that some of the evergreen conifers that have shown considerable damage from this past winter had absolutely no damage following the previous winter(s), even though absolute minimums were as cold or colder.

You are quite right that my observation is limited to those woody plants outside their normal cold hardiness range. It took you a while to get there, but it sounds like you do agree with my basic theory: "...and with which I do not disagree." I think that's the same as, "I would agree."