Noxious Cold

Like a good bit of the rest of the US, we were invaded by a particularly noxious and extreme cold usually confined to the northern polar regions. Fierce winds usually keep that cold where it belongs, but on occasion, that cold travels our way. In early December it became apparent that we had bitterly cold weather coming up. The first order of business was to clean out all of the fall plantings in those pots that were due to have winter arrangements, and take the soil level down four inches from the top. The floral foam form would sit on top of that lowered frozen soil. The form would be anchored into the soil with bamboo stakes, or steel rebar. Pounding a stake down through frozen soil is a good bit easier than chiselling out frozen soil. Three weeks worth of installations were accompanied by this relentless cold. Never have I been happier that we do most of our fabrication for the winter pots in the shop stockroom.

The evergreens in my garden have no where to go, and no other option but to endure. A gardener can provide their evergreens with regular water in the fall. An evergreen with juicy stems and needles is an evergreen dressed properly for the weather. Once the ground freezes, the plants will no longer be able to transmit moisture from the roots to the needles. An evergreen that goes into the dormant season dry is poorly positioned to deal with desiccating winter winds and sun, and the inevitable loss of moisture from transpiration. The water that evaporates from the needled foliage of this yew cannot be replaced until the ground thaws.

That many evergreens have needled foliage as opposed to leaves is a survival mechanism, courtesy of nature. Each needle has a relatively small surface area from which moisture can evaporate. Leaves are poor conservators of water, as they present so much surface area to sun and wind. It is no wonder that deciduous trees and shrubs drop their leaves in the fall.  Carrying a full set of green leaves through the winter would most likely be deadly. At the extreme other end of the spectrum, cactus have evolved to have spines in place of those leaves that are so ill equipped to conserve moisture. Those spines do collect water from rare rains, which then drips down to the roots. Water in some degree is essential to the life of plants. I may let plenty of things go in the garden, but I do water. Plants that do not get the moisture they need are stressed and vulnerable plants.

Of course our long run of cold has me worrying about the boxwood. They are broad leaved evergreens. Those leaves readily desiccate in extreme wind and cold. They are prime candidates for winter burn.  A drench of anti desiccant such as Vapor Gard on both the tops and the bottoms of the leaves coats the surface with a waxy natural compound of pine resin that reduces the evaporation rate. It is amazing what a difference an anti desiccant can make. Any evergreen planting I do after the middle of August gets Vapor Gard ahead of the first winter. It is very inexpensive insurance against disaster. The above picture was taken in April of 2014. These 20 year old shrubs were killed outright from the extreme cold we experienced in the winter of 2013-2014. Double digit below zero temperatures for days on end proved too much for them. The 100 inches of snow we had went beyond insulating them to overloading them with branch cracking weight.

A boxwood disaster is rarely apparent before April. That makes it easy to fret over them all winter.

This day was a heartbreaking day. That day in April made it obvious that the west end section of this old hedge had perished. It succumbed to a once in a lifetime extended cold well below its hardiness limit. The entire summer of 2014 I drove by so many hedges of dead boxwood still in the ground.  I could not have looked at dead plants day after day, and month after month, but disbelief, grief and denial can be very powerful.

Do I think the extreme cold spell we have just had will kill my boxwood? Our coldest temperature was 6 below zero. This is not cold enough to kill a zone 5 shrub. It was cold enough to make me dress from top to bottom for bone chilling cold. I limited the time the corgis spent outdoors. One morning at 4 degrees below zero they came in limping after 3 minutes outdoors. Cold feet. But I do not believe it has been cold enough to seriously damage the boxwood.

Once we finished removing the section of dead plants, we placed big Branch pots in front of the bare ends of the boxwood. It would be every bit of several years before the dead spots and sections would recover from this winter. Note that the tulips coming on sustained no damage from the extreme cold. They were completely dormant, and below ground. Sub shrubs such as lavender, that have live branches above ground in the winter, can be very difficult to winter over.

We did finally get the window boxes and 2 pots in front of the shop done up for winter. They feature cut boxwood twigs stuffed into dry floral foam.  After just a few days outdoors, they began to show the signs of leaf shrinkage from evaporation.

Even the backs of the leaves show signs of stress. As long as these cut stems were packed in wax coated boxes, and not exposed to sun or wind, the leaves were glossy and plump. Once exposed to the weather, they reacted as expected. Fortunately boxwood leaves stay green even as they dry.

I am sure we will have burned and dead tips on these plants come spring, but I expect them to recover.  32 degrees this morning-what a relief.


  1. Jenny Anderson says

    what about broadleaf evergreens like Pieris and Rhododendron? DO they have similar reactions to the extreme winter temps?

    • Deborah Silver says

      Dear Jenny,. yes, other broad leaved evergreens can be damaged. The rhodies and pieris I see here are planted in very protected locations to begin with. Rhododendron leaves are naturally thick and waxy-maybe that helps them survive the winter better. But for sure I never see rhododendron and pieris as beautiful as they are in zone 6 and 7-they are just happier there all around.I have rhododendron that have been in the north side landscape at my house for 25 years.One group still looks good. The other I fear will be gone in a year or two. all the best, Deborah

  2. Virginia Skold says

    I appreciate the depth of your knowledge. It is good to understand what is happening to ones planting’s. Good luck is appreciated as well as normal weather.

    • Deborah Silver says

      Dear Virginia, it seems to me like the weather in Michigan normally tends to extremes. best, Deborah

  3. Catherine Wachs says

    You are right in the need for water going into winter.
    Of course, this is the first year I didn’t use anti-desiccant. Over the years, I haven’t seen a big difference in survival rates. I’ve always believed it was the root system needed to be protected. Boxwoods are very shallow rooted, perhaps the snow cover wasn’t deep enough to protect them?

    • Deborah Silver says

      Dear Catherine,I believe the root system of boxwoods is somewhat protected, as it is underground. But there is a limit to its hardiness. Winter Gem boxwood is hardy to zone 5. So hardy to 15 below zero in zone 5b, and 20 degrees below zero in zone 5a. I like Winter Gem better for overwintering than say Green Velvet, as the leaf size is smaller. best, Deborah

  4. Mary Rosenfeld says

    I’m impressed your lowest temperature was minus 6F. Here, 10 miles NW of Boston, MA, we have had quite a few colder nights, including to -10 and -14. Our winds over the last few days have made for a particularly low wind chill temperature! While we do have some quite frigid days each winter, our Decembers are usually relatively mild. Not this year! But this AM it’s in the twenties and feels positively balmy. Very interesting to follow your information about helping over-winter evergreen shrubs. Boxwood is planted here, but not very much. Yews fare much better in this climate. Along with hedges of lilacs or forsythia. I personally like the trend toward using native shrubs as much as possible, although I don’t know how they fare as hedges. Thanks for your winter update along with the information on preventing desiccation!

  5. I live in Saginaw County and have lavender that are over 30 years old ….however in the winter you mentioned I lost many due to the cold and lack of snow cover. The snow coverage has been the saving grace for these. Would anti dessiccants help for lavender? I had over 40 bushes. I now have approximately 15. I am on a low sand ridge and they grow very well here. I was also thinking of planting a boxwood hedge but now wonder if something else would be better. I live in the country and experience a lot of wind year round.

    • Deborah Silver says

      Dear Lenore, I have no experience with anti dessiccants on lavender. I have always thought that 80% of winter hardiness on lavender involved perfect drainage-it sounds like you have that. Perhaps a hedge of a dwarf needled evergreen would be happier than boxwood over the winter.

  6. I live in zone 6B and in 2014 I lost ten truckloads of plant material. It was heartbreaking. I now apply anti-desiccants on all broadleaf evergreens. It gives me peace of mind, even if we experience a mild winter. Going through these arctic-like periods once again, I am glad I have spent the extra time and money.

    • Deborah Silver says

      De4ar Ginny, it is worth every penny, yes.I have a tree service that can spray Wilt Pruf on very large evergreens for what I think is a nominal cost. My own boxwood are in a neighborhood, which I think offers them protection from sun scald.And I water them if they need it right up to the time the ground freezes. I think that is key. I did not lose a single boxwood the winter of 2013-2014, but I did have some minor damage. best regards, Deborah

  7. Karen Heath says

    Thanks for the info. I transplanted six medium size boxwoods in August or September and tried to keep them watered through the fall. I’m sure they could have benefitted from a coat of anti desiccant. Is it possible to apply this during a warm period? I am in Grosse Pointe.

    • Deborah Silver says

      Dear Karen, anti dessiccants usually need to be applied around Thanksgiving.The temperature needs to be 50 degrees, and you need a dry period so the spray adheres and dries thoroughly. We have weather in the 50’s forecast for later this week-what could it hurt to try? Spray the heck out of them-it is a natural material that can do not harm. To help it has to stick. If it does, good. If it doesn’t no foul. I would try it. all the best, Deborah

  8. This continues to be a winter of extreme cold weather. My 5-7 ft. tall rhododendrons look stressed, plus the deer are eating the leaves. By Spring, I’ll have no leaves and will prune the bushes back. Surprisingly this cycle repeats every couple years. The bushes go from 5-7 feet to about 1-2 feet and then bounce back. That said, I’ll have no flowers for a few years. My Fall newly planted 9 Norway Spruce seem to be just fine. Like you, I watered everything in prep for Winter months. Because of the large deer population, I avoid planting anything they like to eat. The one exception is the rhododendrons and they were planted about 25 years ago, before the deer population exploded. Your boxwood is really beautiful, but it would not survive the deer in my location. Winter kill is disappointing, especially when it hits mature plantings.

    • Deborah Silver says

      Dear Susan, I do have deer go through the shop on occasion. Mostly in the spring, when they chop off some tulips and chew the pansies down to the soil level in a pot we have by the road. We spray and spray again to keep them away-that works. I do not have deer at home. I live in an urban neighborhood just a block from a major 4 lane city road. Animal kill is one thing, but winter kill can be mitigated with good culture, fall watering, and anti dessiccant. Nature calls the rest. I had mature roses terribly damaged and finally killed off over the 2013 and 2014 winters here. It was very discouraging, but I finally did replant. Next year I should see some roses. all the best, Deborah

  9. Diane Miller says

    I live in northwest Ohio and we have had -10 this year. In the past I have used wllt proof on my rhododendron successfully. And like you Deborah, have used it on boxwoods as well. As far as
    lavender I don’t think it would work because of it having fuzzy leaves. And I agree with you it is in the drainage for lavender. An added note on Wilt Proof, I recently retired from a garden center and one summer we had an elderly gentleman come in to purchase Wilt Proof. We were experiencing a drought, and he sprayed his plants to retain their summer moisture. It says on the bottle it can be used in that manner, but I had never talked to anyone that used it that way. He used wilt proof ever summer. May have also carried over into winter moisture retention. Thank you for all the good info and great pictures, I really enjoy reading about all the creative projects you and your team get into. Happy Gardening!

  10. Carol Johnson says

    Would you use this vapor guard every year as a preventive measure? If so when would you apply it? Also if you have a mild winter will it hurt the plant? I do landscaping at a gold course in South Carolina we don’t usually have the cold temperatures that we have had this year but this year has been brutal. Wish I had known about this earlier as we planted over 100 boxwoods for a hedge along our driving range.

    • Deborah Silver says

      Dear Carol, Vapor Gard is a natural waxy compound made from pine resin. It is harmless to boxwood. I recently read about a man who vapor gards his plants in the heat of the summer so they don’t need watering so often! best, Deborah

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