Every fall somebody in a palm group posts the same triumphant line. It made it through winter, so it's officially hardy in my zone. I want to believe that as much as anyone. I just don't, not anymore.
Here's the thing nobody wants to hear when they're standing over a palm that just leafed out in April. Surviving winter and being hardy are not the same claim. One is a data point. The other is a pattern, and you don't get a pattern from one data point no matter how badly you want one.
I've got a Sabal palmetto in the ground in my front yard about to find this out, one way or the other. It went in May 2026, cruised through its first summer on the rootzone cable, and now it's staring down its first Wisconsin winter. If it comes through clean, I'm not going to tell you Sabal palmetto is proven hardy in zone 5b/6a. I'm going to tell you it survived one winter. Those are two different sentences, and I plan on keeping them different.
Part of why I'm careful about this is the forecast. Early signs point to a strong El Nino pattern this winter, which historically means a milder, less snowy season here in southeastern Wisconsin. That sounds like good news, and honestly it is, but it's also the worst possible winter to learn anything from. A winter that never really tests a plant doesn't tell you the plant can pass a test. It tells you the test didn't happen this year.
I've watched this play out with my own windmill palms. The one I lost in December 2017 hadn't failed a cold night. It failed six straight days where the high never climbed back above freezing. The one I've got now is heading into its fourth winter in the ground, and every one of those winters has looked different. Some brought single digit lows with a warm afternoon right behind them. Others just sat cold and gray for a week straight. That variety is what actually builds a track record. The count of winters matters less than what each one asked of the plant.
There's a real number behind this, too. Growers who've tracked cold hardy palms for years generally land on the same rule of thumb, that it takes at least two full winters, ideally with some real range in how nasty they get, before you can call a planting proven. One clean winter, especially a mild one, is closer to a coin flip than a verdict.
So if you planted something borderline this year and it comes through fine come April, enjoy it. Take the photo. Just don't retire the protection system yet. I won't be retiring mine on the sabal palmetto, mild winter or not. Ask me again after it's seen a bad one.
Until next time,
— Tim
