What!? A USDA Zone 6 Plant Thrives in Minnesota?

Hey, it’s back! Labeled USDA Zone 6 hardy, this hyssop survived winter in my zone 4 garden.

Pictured above is an anise hyssop that I planted last summer for a little color with absolutely no hopes that it would survive the winter.  Yet, come April, it was sprouting its pretty chartreuse leaves and getting ready for another season of bloom.

The plant is ‘Golden Jubilee’ anise hyssop (Agastache foeniculum ‘Golden Jubilee’), a 2003 All-American Selections winner that has pretty purple bottlebrush flowers and is very attractive to bees, butterflies and hummingbirds. It’s listed as being hardy to USDA Zone 6 on the tag it came with, though I’ve found several other sources that says it is zone 5 hardy. (For reference, I live in zone 4, which covers the southern two-thirds or so of Minnesota.) Even if it was zone 5, I would not have expected it to survive the winter of 2016-17 because of the lack of snow cover. We did have a warm winter overall, but the temperature sunk to below -20 F in December, which should have been cold enough to ice even a zone 5 plant.

This is what it looks like in the summer. Photo courtesy of All-America Selections.

But like all politics, all weather—and all gardening—is local. In my garden, this plant faces south. I live in the urban heat island of St. Paul. The plant lies within 5 feet of the foundation of my house, which may emanate some heat. The extremely cold days in December came right after a snow storm, so the plant’s roots had some cover during the worst of the winter. Clearly, the local conditions were warm enough to get it through the winter.

It may also be that the zone 6 rating given the plant by this grower is conservative. That’s one thing to keep in mind when choosing plants—zone ratings are as much art as science and some companies are conservative in their ratings while others are more optimistic. Your local conditions may be warmer or cooler than the averages for your zone, too. Choose plants not exclusively by the numbers but by the local conditions.  I bought the anise hyssop plants later in the summer. They were on sale and I expected they would be annuals. This brings to mind a good rule for gardeners who want to “push their zone.” Never choose a plant you can’t afford to lose.

Whether it was luck, a warm winter or a too-conservative rating, I’m happy to have this cheerful plant back for another year.


6 Replies to “What!? A USDA Zone 6 Plant Thrives in Minnesota?”

  1. A self sown verbena bonariensis from last summer landed against the fence where the neighborhood leaves pile up every fall and winter. I was pretty shocked to see it when I cleared away the leaves for my bulbs. I dug up my agastache to bring indoors for the winter but it did not survive, I should have just left it where it was. My garden is in the little slice of zone 4 that spreads from Minnesota into the Oneota River Valley of Iowa.

  2. There are some Japanese maples in our neighborhood, and they are beautiful. I’m not sure I’m going to plant one though.

  3. I have some Agastache Rupestris in my garden (in Northfield) that has come back reliably for the last 3 years– also have one wee Japanese Maple Bloodgood in the ground for the last 3 years. I overwinter some other zone-inappropriate trees in the garage and the house. I’m always prepared to lose them, but so far so good!

  4. I live on the border of zones 3 and 4, I have had anise hyssop growing in my garden for years! Not only does it grow, but it reseeds and multiplies! I love it for the pretty chartreuse leaves.

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