How to Help Gardens Weather Winter Storms

With a sunny, happy winter day tucked in for the night on Sunday, it seems it was the calm before the storm.  

Sitting in my home office loft writing and looking out at the clear, twinkling, movie-set New York skyline just beyond, it seemed unholy to think that in a short time, we’d be bracing for a whopper of a winter storm.  It’s already been labeled #Snowmaggedon2015.  And then it wasn’t.  Somewhat of a bust of a storm but still a whopper.

I’ve just about completed the Recommended Garden books review for Garden Glamour friends and fans.  With nearly a dozen garden and horticulture books featured in my list of recommendations from 2014’s just-published or discovered/introduced to me at events, symposiums, or lectures, this is a gardening, growing, and breeding book list you won’t want to miss.

However, with the news’ escalating drama for 2015’s first major winter snowstorm changing up, forecasters are now calling for a major blizzard.

Therefore, I thought I should change things up, too.

Gardens and plants are resilient, we know.  

Yet judging by even my New York Botanical Garden’s Landscape Design alumni group, concerns about the extreme cold and its lasting effect on the plants is on high concern alert.  One member wrote to ask last week -- before the blizzard warning -- if there is anything any of us could recommend so that her beloved hydrangeas would be in good form to charm the expected visitors to her slice of Eden as part of a larger garden tour.

Last year, as many of you know, the growing season lost the charm and beauty of many of our most beloved summer favorites - especially the flowering hydrangeas - specifically, the Hydrangea macrophylla - the bigleaf or “mophead” hydrangea that gently whispers “summer.”

I adore them.  I inherited the ‘Nikko Blue’ when we moved to our home and added the ‘Lady in Red’ as sassy, summer accessories to the red roses that border the Coral Bark arbor design I did some years ago.

In turn, I use these red and blue beauties to great effect for our Independence Day Fireworks party when friends and family gather to officially kick off the summer, celebrate Mother’s birthday! and watch the fireworks set off in the marina right below us.  It’s grand ol’ flag kind of an affair.

So all can imagine the vast disappointment when last year yielded no/zilch/nada hydrangea blossoms.  Not only the beloved hydrangeas were a no-show, many other woody perennials such as caryopteris, and some evergreen shrubs, including Cherry Laurel, Prunus laurocerasus suffered.  

It wasn’t like we didn’t see it coming.

No. Those of us in the garden design and horticulture tribes had been steeling ourselves for some months, hoping for that miracle that Mother Nature can provide.  It was not meant to be.

However, their “failure to launch” was not due to the Polar Vortex or the bracing winter cold that strangled most of the Northeast last winter.  I don’t want to dismiss the plunge -- It didn’t help to have record-breaking cold. But that’s only a part of the story.

Want more irony/confusion?  2014 was the warmest winter on record - overall -- according to NOAA and NASA, among other leading authorities.  

The issue is climate change -- it’s not global warming as sceptics or #ClimateOstrichs who insist on sticking their head in the rapidly decaying soil want to do.

Plants are not unlike the canary in the coal mine.

See, it’s the wide and rapid temperature swings that affect the health of the plants -- and of course wildlife, including insects and birds and reptiles and…

When folks say, “Geez - I remember it was really cold/a lot colder when I was a kid - so what’s all the fuss?”  They’re missing the point.

The difference or issue is used to be the gradual, predictable ramping up to the cold and the sustained, predictable duration.  

When it comes to the plants - is they can take the cold. They can and in some instances need the cold - and enduring cold.  

The freeze eliminates pests including insects, pathogens, even mosquitoes.

Woody Perennials, shrubs, and trees go dormant.  According to  North Carolina State University Cooperative Extension (NCSU), “As temperatures drop, growth slows and many plants begin winter acclimation.  Cool temperatures and shorter days initiate the first phase of hardening, allowing plants to withstand a frost but not a hard freeze.”

Accordingly, “To become fully acclimated so they can tolerate the cold associated with their hardiness zone, nursery crops require exposure to temperatures between 32°F and 40°F followed by temperatures slightly below freezing.

After plants become fully hardened, prolonged periods of warm weather can cause them to lose some degree of hardiness even if all other factors are favorable.”

And that was the first punch.  The hard freeze came so fast and furious, the plants normal rhythms were disrupted.

Then, there was a late frost in the spring - just as the woody perennials “sap”  was starting flow.  Essentially, it was like blood freezing in the veins.  

I waited until the last possible moment and then cut the woody stems.  

Normally, one does not prune or cut the woody stems of the hydrangea macrophylla because they bloom on old wood.  However, last spring’s circumstances were extraordinary.  So the cuts/pruning was made.  It was the sacrifice that was needed.  And the hydrangea leaves came back full and green.   No blossoms, of course, but the plants came back healthy.  Gardening is a hopeful pursuit.

The cherry laurels surrounding our water garden survived the winter with elegance and grace - I wrote about them on Garden Glamour: Splendor in the Snow last year, noting they looked for all the world like ballerinas in repose after one heavy snow storm. Yet they bounced back with equal amounts of grace and strength.  

 

The late spring frost however was their undoing.  

Then, a kind of pathogen seemed to settle in.  After I determined the shrubs needed to have the compromised leaves removed, we - my husband and mother and me - raced to implement this course of action.  The curious result - if you can call it that - is that the meticulous removal of the leaves on the cherry laurels on one half of the water garden rebounded with dark green color and rich, robust foliage.  The other half? Not so much.

Why? You will ask, as a logical garden question.  The crazy, true answer is that were not meticulous enough to remove all of the compromised foliage -- it was getting dark that late spring day, it was still rather cold, it was a Sunday, and my husband and mother were getting tired and cold.  Me too.  Plus, I wasn’t all that positive that my solution strategy would work - so we had to call it quitting time.  

As you can readily see, the strategy worked on those cherry laurels where we remove the compromised leaves.   I fretted all summer that I didn’t stay out in the dark to complete the work on the other shrubs.  Oh, we took away a lot of their leaves but not the ruthless, surgical work we did on the other half of the border…  The contrast is striking. 

Meticulous leaf removal resulted in rich, robust shrubs

The not-so-primped shrubs were thin. Leaves didn't fully rebound all season

Normally, blossoms bloom on the old wood - last year the hydrangea's useless/frost damaged wood had to be cut.  Here you can see the leaves came back so pruned out the woody stems.

April 16th snow/frost punched out the woody perennials

Trying to create Spring Containers was too challenging last Spring!

Here you can see the snows on the nursery plants in April

Researching data for this article, I see that my instincts were right:                                                                                                  

Indirect Damage

                                   

The experts indicated the plants may not be killed outright but can be stressed to the point that it is predisposed to infection or infestation from pests that eventually kill it. In fact, indirect effects of cold may occur more commonly than direct kills and manifest themselves as cankers, collar rots, and dieback because of attack by fungal and bacterial parasites. Sometimes disease damage is the only outward sign of freezing damage.

This is according to MSU Extension  

Here, writer Lee Schmelzer cites “Winter Damage” as a broad term that refers to damage in fall (!), winter, and early spring (! – my exclamation point to note his “winter” is every season except summer!)

He says fundamentally nearly all winter damage is desiccation -- freezing cellular water or indirectly by freezing soil water making it unavailable for uptake. I refer to this as “sap-stop. “

What the wild swings in temperature do is to wreak the kind of havoc we witnessed last year.
My experienced nurseryman told me that the plants suffered because of a double punch.  

The first, early frost occurred as a surprise.  The nurseries tried watering them to get the ice to protect/heat the plants but the storm came too fast without much warning - thereby rendering most of their efforts unsuccessful.  The plants didn’t die - they just rather seized up - as the “sap” was still flowing in these woody perennials’ stems.

The second tragedy occurred with a late spring frost. Just as the cellular water was flowing – and we gardeners could see the buds on the woody stems – the frost caused the “sap-stop.”  We know how that turned out in the end.  No blooms last summer.

Schmelzer explains cold kills by denaturing proteins: “Plant proteins, among them enzymes, are temperature sensitive and must remain intact and in the presence of liquid water to remain functional. Cold inactivates proteins by making liquid water unavailable for their function.”

Want to help plan your garden with an eye to your zone’s Frost/Freeze dates?  The Farmer's Almanac does it for you. (It’s official name is the “Old” Farmer’s Almanac but I’m just thinking that Old and Farmer is sadly redundant.  We need young farmers and not just in urban farming.  

We need to reclaim the “corporate farms.”  But that’s another story for another day.

The other winter issues you’ll need to monitor are Frost Burn, Wind Burn, as well as Desiccation.

A few years ago when the winter snow storms started back with a vengeance, I wrapped our arborvitaes in sheets after I swept the heavy snow off of them in order to prevent the snow from getting inside and weighting them down.  It worked.

And I probably should apologize to the neighbors for making the garden look a little like a laundry room. Ha. Plus, I used panty hose to help shake the snow off. Never a dull moment in the world of gardens.

Read here on Garden Glamour: SOS Save Our Shrubs It’s a post I did some years ago about winter storm care for shrubs and trees.  Lots of good information and references.

Let me know how your garden fared the storm.  And be sure to enjoy the winter garden.