Hardy Rosemary?


Lavender in the snow–too early to prune!

On this cold, snowy Tuesday, I’m thinking about plant hardiness.  It’s amazing what plants can take, even with the extremes we’ve seen this past year. Two of my favorite plants are lavender and rosemary.  I’ve had lavender live for almost 20 years in my Mediterranean rock garden, but the time I tried rosemary in that garden, it lasted one winter and died the next. Why do I want to grow rosemary in my garden? It’s extremely drought tolerant. It smells good. It has beautiful blue flowers.  It’s evergreen. It is both a culinary and medicinal herb.

My friend and colleague, Reta Zane, went to Santa Fe for the Herbfest this past weekend and heard Jim Long lecture on how to get rosemary to winter in your garden.  I was very intrigued by what he had to say about it.

First, he said that two varieties, Hill Hardy and Arp, are the hardiest rosemaries and the ones most likely to succeed. I’d read that before, but it’s nice to have it confirmed by an experienced herbalist like Mr. Long.  Next he said to start with the biggest plant you can find, plant it in your garden in spring and dig it up in the fall! Winter it over indoors in a cool room (62 degrees) and water it once a month. The next spring, plant it out in your garden where you want it to remain.  If there are times in that second year in the garden, fall, winter, or spring, where the temperature is predicted to dip drastically, like from 70 degrees one day to 15 the next, cover the trunk of the rosemary with a piece of Remay, wrapped loosely around it.  Jim Long said that cold temperatures don’t kill the rosemary, but warm temperatures followed by extreme cold do. And, he said, it is at the trunk, near the soil line, where the plant is most likely to split its bark–a certain prelude to death.

That part about the split bark was also very interesting to me because the Arp rosemary that died in my garden had a very obvious split in the bark near the soil! We call rosemary and lavender herbs, but they are shrubs, too, with woody trunks and stems.

He recommended pruning all Mediterranean herbs very hard. Herbs like rosemary, lavender, oregano and thyme could have as much as 1/2 taken off once they break dormancy in spring, he said.  In my experience that hasn’t been such a good plan. The lavender plant that has lived for so many years in my garden gets a very light pruning every year. I did prune another lavender, taking off almost a third of its height, in a different part of that garden, but it didn’t seem to like it and died slowly over the next year. What I can’t remember, and what makes anecdotal evidence less useful, is whether that lavender was not doing well when I pruned it–maybe that’s why I pruned it so hard.  Then we can’t conclude that pruning killed it, but maybe only hastened its death. Nevertheless, I’m hesitant to consider hard pruning all my Mediterranean herbs.

Jim Long lives in the Missouri Ozarks, a different climate from the Colorado Front Range, but it has similarities. It can go from very warm one day to icy cold the next.  The coldest recorded temperature there is -15 F., while for my garden it is -23 F.

I can also add that the people in Colorado who have success growing rosemary outdoors in their garden (and I know more than one) have it in a protected spot–on the east side of their house or wall, protected from Chinook winds.  One woman I know had her plant in a courtyard and it was huge and gorgeous.

I’m going to try again this year and I’ll keep you informed of my success or failure.

Rosemary, overwintered in a cool greenhouse:

Rosemary 'Arp' in the clay pot in front.

Rosemary ‘Arp’ in the clay pot in front.





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