overwintering rosemary, indoors and out

THIS ONE COMES UP EVERY FALL (especially from gardeners in Zones less favorable for it than 7ish): How do I keep my rosemary plant happy all winter? The answer: Cool sunshine—that rarest of indoor conditions in a heated house in the year’s darkest days, and not a guaranteed steady diet weather-wise outdoors many places, either. How to accommodate Rosmarinus officinalis, outdoors or in.  

Start with a cold-hardy cultivar if you plant to try to overwinter rosemary in the ground in other than a truly frost-free hardiness zone. ‘Arp’ is the best known, along with ‘Hill Hardy’ (also known as ‘Madalene Hill’ after the late herb gardener from Texas; ‘Arp’ was her discovery, by the way, the result of her search for plants that could take not extremes of cold but the Texas heat). Oregon-based Nichols Garden Nursery’s owner touts ‘Nichols Select’ as being a toughie, too.

It’s “as hardy as any I’ve grown, probably Zone 6B, and the flavor is terrific,” said Rose Marie Nichols McGee in our springtime interview. “It was planted 25 years ago at our home and survived minus-7 degrees F once. I think this is your best for a long-lived rosemary.”

The U.S. National Arboretum website reports on trials of more than four-dozen cultivars of rosemary, and how they fare on all scores. Even in USDA Zone 7a, the gardeners there take the precautionary measure of taking cuttings from the collection, in case winter causes havoc that cannot be anticipated with the herb-garden inhabitants. (I pinch or prune my rosemary back a bit–not to start cuttings, but to freeze the delicious sprigs for use in winter, and keep the plant tighter.)

Proper location and care will help keep the well-chosen plant happy. Nichols McGee advises “helping it along with some lime or bone meal worked into the soil and provide good drainage,” and planting rosemary in a well-drained position with six hours a day or more of direct or very slightly filtered sunlight. Many Zone 6ish Northerners optimistically try one of those extra-hardy cultivars planted in a sheltered spot, such as by a wall, and then mulch heavily after frost.

“What is hardest on our woody plants, including rosemary,” she adds, “is wet soil followed by temps that drop way down near zero then warm and drop again with considerable frost heaving.” In her Pacific Northwest location, she says they don’t mulch around the trunk and root zone, “but do make generous use of garden blankets, throwing one or two layers over plants we’re worried about.”

For container-grown plants, she says, whenever temps are going down to the low 20s all rosemary will benefit from protection. “If you have a garage or cool porch, pull your plant into this sheltered area until the harsh cold passes (which might be all winter in the colder zones; make sure the garage or porch will stay a safe temp throughout the needed timespan). Move it back to its regular position when temperatures moderate.”

So what if there is no such spot, if even with a temporary garden blanket it’s just too tough outside where you live? Here’s where the “cool sunshine” trick really gets tricky. You’ll be looking for a spot near a sunny, southern window (west might also work), where the temperature is around 50 to 60 degrees.  My mudroom is right, I think, so that’s what I will try—but many of us don’t have enough light in winter. Think about adding a supplemental plant light–which can really help with many tender things that keep their leaves year-round like rosemary. We’ve all seen rosemary and other evergreens being tortured indoors with too little light get all stretched out, or etiolated.

Have a rosemary in the ground that you fear should have been in a pot, so it could come indoors? A third option would have been to dig it and pot it up for the winter, but that’s best done around Labor Day, to give the plant a chance to adapt to its new tight quarters before the added shock of indoor life begins. A very fast-draining mixture–perhaps with a few inches of gravel at the bottom of a generous-sized pot for added insurance–is best.

Very important: Don’t overwater. Remember, no wet feet, especially in winter—whether that’s inside or out, in a pot or in the ground.

41 comments
October 18, 2012

comments

  1. Alejandro says

    There’s a Rosemary (Madelline Hill) that’s hardy up to zone 6, at least according to the guys of Digging Dog .I’m in zone 5b. I’ll give it a try this winter and let you know…

  2. Brian G. says

    Do you suppose this would work with my little bay laurel? I just dug it up and potted it today to spend the winter with me in my apartment. I only have an eastern facing window but it is a very chilly spot all winter.

  3. says

    This post is so timely! I’ve been looking for words of wisdom on this subject! I just planted a mature rosemary plant this summer in a planter’s box, and I’m hoping for the best this winter! Just one question, how does the blanket thing work? How do they get sun if they’re covered in blankets?

  4. Reed says

    Brian, I winter my bay laurel right alongside the rosemary in a room with east facing windows. The cool season temperature in there is generally mid-60s. Does great.

  5. says

    I am going to try outdoor overwintering my rosemary this year… it will be the first time I try this, but since the rosemary I overwintered inside died last year, what do I have to lose and it may survive the cold :) Luckily is it in spot where it will get a lot of sun even through the winter, so wish me luck!

  6. Carol says

    My rosemary looks very happy in a raised bed outside facing east in zone 8. This will be its third winter. I just leave it in that spot next to the house. We get plenty of rain here in western Oregon and last winter the temperature was at least as low as 30 degrees for short periods. I find it to be tougher than most of you seem to think.

    –Carol

  7. Carol says

    I just checked my records and the rosemary I have is an offshoot of ‘prostratus’ called ‘Irene’ which was found in California a few years ago. It has large blue-violet flowers and looks lovely cascading over a wall. It is flowering right now and is so striking I am thinking of putting a couple of them along my retaining wall in the front of the house next spring.

    –Carol

  8. LaRieta says

    My Rosemary is in a raised flower bed next to my sage plant in Texas.
    They were not watered well , sorry to say ( I was away traveling.)
    they are beautiful..bushy and smell great now that I’m home and giving them love and water. smiles)))
    Wish I could say the same for my California Poppy …
    the seeds came up but they are all gone this morning…
    Anybody grow Poppy ?
    LaRieta

  9. Sara B says

    When I’ve had rosemary inside for the winter, I’ve gotten it to about March looking great and then all of a sudden it dries out and dies. I’ve kind of given up on it.

  10. Bernie Zimmerman says

    I have tried at least 3 times to dig up my rosemary plant, but unfortunately each time it dries up & dies in the house. When left out in Erie’s Pa. zone 5 it freezes. It is now October’s end & I see it out my window. I’ve cut some to bring in & dry for cooking. But my heart is breaking knowing it will probably die over winter. What type of blanket can i use? Will thick leaf mulch work?

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