2019 Winter Impact on Hydrangeas

Time to report on 2019 winter impact on hydrangeas.
In early May, I went out to my Zone 5 garden to see what the past winter had done to my hydrangeas that bloom on old wood: big leaf (macrophylla) and mountain hydrangea (serrata). I also checked on the oak leaf (quercifolia) and climbing (petiolaris) hydrangeas I grow. 


I held my breath as I always do. The winter brought several episodes of severe cold temps. One came early in November 2018 when the plants had not had a chance to fully harden off. Then came 2019 with some significantly icy temps. The chart below shows multiple scattered January and February temps taken from my closest official weather station:

Weather chart showing extremely low winter temperatures

Extremely low winter temperatures and early season freezes are two ways hydrangea flower buds are killed.

The winter weather was compounded by a significantly cool and wet spring. Everything was late breaking dormancy, not just hydrangeas. By May 31, all my oak leaf and climbing hydrangeas finally showed their buds. My ‘Alice’ oak leafs had significant winterkill of entire branches. It makes sense as they are much more exposed to the weather by virtue of their sheer size and where I have them sited, especially in view of the cold winter. I completely lost one 10 year-old oak leaf hydrangea. I believe it was much too wet both last fall and this past spring. Oak leafs are the one variety that can not take wet conditions. I have replanted that “hole” with offshoots from a colony of woodland hydrangea ‘Annabelle’ which is already flowering. 


Then I inspected my big leaf hydrangeas (macrophylla). I have a variety of rebloomers* (see list below). I also have some old wood macrophyllas like Lady In Red. They are scattered throughout various parts of my property with different levels of exposure to the elements. Here’s what I found.
Consistent with prior years, the buds on one Lady In Red were alive and well. However, despite being protected from the prevailing weather by a neighbor’s house, it had significant winter kill of entire stems. This was also the plant that got mangled by a freak tornado in 2018. Following that event, she got a severe cut back and reshaping after flowering. I suspect she was weakened by the correcting action we took to repair her. The second Lady In Red had similar winter kill: some tips and stems were clearly dead and showed no signs of life while other tips had buds on them.


On to inspect my collection of Endless Summer®, The Original. Some had complete dieback, as shown in this photo (it’s regenerating from the base).

Winter temps killed all old wood hydrangea stems

Big leaf hydrangeas will grow new stems after winter kills the old ones.

Some had partial tip dieback; some had partial stem dieback or full stem death. Below is a photo of one that had a little of everything. The fence helped somewhat to protect it. The same happened to most of the other rebloomers I have* (see list at the end).

Photo of hydrangea showing partial winterkill

Big leaf hydrangea shows partial winterkill.

BloomStruck® came through the best of all my Endless Summer® hydrangeas. I have three of them planted (in various locations for testing purposes). All three lost all their terminal flower buds that were produced last year. One had tons of buds coming off the side shoots (lateral buds). This is the magic of rebloomers! If the stem makes it through the winter, it can give you flowers despite losing the one at its tip. One BloomStruck® had complete dieback of all its stems and is regenerating from the base. The third had a little of both: some total stem dieback and some lateral buds. The flowers are just starting (late June in CT) to color up.

BloomStruck® reblooming hydrangea with flower buds from reblooming stems.

BloomStruck® hydrangea can flower from reblooming stems after winter kills terminal buds.


This picture below shows a tip that you might have thought was dead in April or even mid-May and you might have cut it off. But by early June, it actually produced a flower bud. The Lesson: Be patient when it comes to cleaning up your plants in spring and wait to see “broccoli” before you cut those stems.
Dead-looking hydrangea tip with bud emerging

A dead-looking hydrangea tip may produce a viable bud.



However, the most impressive bigleaf hydrangea for me this season is a new acquisition: Blue Enchantress®.  Commanding ruby-black stems support showy mophead flowers on this exquisite reblooming hydrangea. All terminal buds were killed by the winter temps, but since it’s a rebloomer and hardy to Zone 4, the flowers are coming from the side shoots. See the below photo collage.
Reblooming big leaf hydrangea macrophylla Blue Enchantress showing many buds on black reblooming stems

Despite winter impact on terminal buds, reblooming big leaf hydrangea (macrophylla) Blue Enchantress® produced many flowers on black reblooming stems.

The other winners that are absolutely superb are all the newly planted Tuff Stuff reblooming mountain hydrangeas. I followed my own advice last year and donated some of my underperforming plants and replaced them with hydrangea Serrata Tuff Stuff™. Although all my mountain hydrangeas have buds on them, this variety broke dormancy the earliest of all. Regardless of where they are sited, they are now a kaleidoscope of color.


When I analyze which of my plants did what, the two major conclusions I drew last year still hold:
            First, the plants that did the best were those that enjoyed winter protection from one or more of several sitings: dry winter persistent foliage which might have been needled conifers like Alberta spruces or overhead junipers. They might have had oaks that held their foliage and helped block icy winter winds. In some cases, there was a garden shed or a house or fence which served as protection. Rhododendrons and azaleas also protected some plants. Between the weather and the protection they had, they have reacted as if they were in a warmer zone. Keep in mind that I don’t wrap any of my plants.
            My second conclusion is that in my cold zone 5b, reblooming hydrangea macrophyllas and serratas are the only way to go. Despite losing all of their tips, the reblooming stems are what will contribute to my garden from now until frost. If you garden in a cold climate or are subjected to wild fluctuations in temperatures, rebloomers will deliver the garden color and interest you need and want. 
The good news for me this season is I don’t have to wait for a ”second” later flowering cycle since most rebloomers had buds a few weeks back and now I have flowers in June that will age beautifully all season long. 


Rebloomers are not just for cold climate gardeners. That reblooming capability can only improve garden performance in any zone as healthy reblooming plants pump out more and more flowers.
*Other rebloomers I assessed:
  • Endless Summer® Blushing Bride, and TwistnShout®
  • David Ramsey
  • Double Delights™ Wedding Gown, Perfection, and Star Gazer
  • Everlasting™ Revolution
  • Forever & Ever® Peppermint
  • Let’s Dance® Blue Jangles®
  • Midnight Duchess®
  • Mini Penny™
  • Nantucket Blue™
  • ‘Penny Mac’
  • Pink Shira™
  • Queen Of Pearls®



On another note, I will be signing books and presenting a talk (Foolproof Hydrangeas) on hydrangeas tomorrow, June 29 at 10 a.m. at White Flower Farm.  There is a fee for this program and registration is required. One FREE 1 qt perennial will be given to each attendee. Light refreshments will be served. I was just there last week for the annual tent sale and roamed the display gardens and hydrangeas for sale. The gardens look great and the retail store has a wide selection of hydrangeas. If you’re in the area, do stop in. You won’t be disappointed. If you can’t make this one, check the calendar tab of my website to see where else I will be. over the next few weeks.


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