What Happens to Plants After an Untimely Freeze Part 2

by Kathy Purdy on June 1, 2009 · 13 comments

in FAQ, Weather

front lawn after hard freeze

In Part 1 I mentioned the two hard frosts and a freeze we had recently, all of them rather later in the season than is typical. I illustrated how different species in the same genus reacted to the freeze differently, and also gave examples of plants that were damaged even though they were protected.

Appearances Can Be Deceiving

Sometimes frost damage doesn’t show up right away.

This Forever&Ever hydrangea was covered with leaves and the sprouts poking through the leaves were covered with a container. The morning after the big freeze, the damage is barely discernible as a slight shine and darker color.

This Forever&Ever hydrangea was covered with leaves and the sprouts poking through the leaves were covered with a container. The morning after the big freeze, the damage is barely discernible as a slight shine and darker color.

The Forever&Ever hydrangeas are a special form of Hydrangea macrophylla. The leaves put out new growth early, but that growth is frost sensitive. In our cold climate, the buds that produce flowers must be protected from freezing. I mostly do this with a thick covering of leaves, but this shrub was putting out growth beyond the leaves piled around it. I covered this growth with a container, which was sufficient for the first two heavy frosts, but not the big freeze.
Several days later, the damage is much more apparent

Several days later, the damage is much more apparent


On the other hand…
This columbine was completely unprotected for the hard freeze and looks pretty pitiful

This columbine was completely unprotected for the hard freeze and looks pretty pitiful


Just hours later, it looks like it never was frozen. No damage whatsoever.

Just hours later, it looks like it never was frozen. No damage whatsoever.

Too Big to Protect

Trees and shrubs often take the worst hits from unexpectedly cold weather because they can’t be covered. We are always dreading frost when the apple trees are blooming, and this Michigan State University Extension site explains how to assess frost damage to apple buds, flowers, fruit and trees. The photo below illustrates how woody plants can vary in their resistance to cold damage.

The maple leaves were undamaged, but the choke cherry leaves were all destroyed.

The maple leaves were undamaged, but the choke cherry leaves were all destroyed.

We gathered several bouquets of lilacs the night before, certain they would all be reduced to brown mush.
The freeze didn't ruin the lilacs, to our surprise.

The freeze didn't ruin the lilacs, to our surprise.

The florets that were past their prime turned brown prematurely, but most flower trusses went on to bloom normally and perfume the air wonderfully.

The florets that were past their prime turned brown prematurely, but most flower trusses went on to bloom normally and perfume the air wonderfully.

Some Plants Can Take It

Border phlox and Siberian iris foliage took the hard freeze in stride.

Border phlox and Siberian iris foliage took the hard freeze in stride.

What You Should Learn From This

When the forecast reads,

Temperatures Monday morning will fall into the upper 20s to lower 30s. Sheltered rural valleys could be even colder…Those with agricultural or gardening interests in the warned area are advised to protect tender vegetation.

don’t throw your hands up in despair. Even if you can’t completely protect your plants, you can help many of them either to recover for this season, or to build up strength for next season. You won’t know how much you can save until after it’s all over, so don’t assume it’s hopeless ahead of time.

About

Kathy Purdy is a colchicum evangelist, converting unsuspecting gardeners into colchicophiles. She would be delighted to speak to your group about colchicums or other gardening topics. Kathy's been writing since 4th grade, gardening since high school, and blogging since 2002.

In the end, this may be the most important thing about frost: Frost slows us down. In spring, it tempers our eagerness. In fall, it brings closure and rest. In our gotta-go world--where every nanosecond seems to count--slowness can be a great gift. So rather than see Jack Frost as an adversary, you could choose to greet him as a friend.
Philip Harnden

{ 12 comments… read them below or add one }

Susan in Calgary Canada May 13, 2012 at 2:12 pm

I have a Schubert Chokecherry tree and it started to bud out in March during a warm spell but since then we have had some very cold and wintery days in April and May. The buds are very small and seem to have been stunted. Will this tree get buds, leaves or flowers this year? Will this kill the tree?

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Kathy Purdy May 13, 2012 at 3:23 pm

My guess (and it’s only a guess) is that you won’t get flowers, but you will get leaves. And of course, no flowers means no fruit. It shouldn’t kill the tree unless it was already stressed by something else (disease, root compaction, drought, etc.).

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dona hand April 28, 2012 at 8:06 pm

i started my dahlias indoors, then because it was so nice i pleeanted them outside, big mistake, yylost to frost, cut foilage all off, .will they come back

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Kathy Purdy April 28, 2012 at 8:08 pm

They might. What have you got to lose?

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Jackie May 25, 2010 at 12:01 pm

I covered my new spring planted endless summer hydrangea with dead leaves in the fall. This Spring, after removing the leaves close to the base of the plant, I pruned it back quite low to promote a bushy plant. It started to grow beautifully, but then the threat of frosts came.[Big surprise]. Icovered the plant both nights with two layers of sheets and fortunately, it was not harmed. It is now the size it was before I pruned it![May25]. I am new to growing this hydrangea, so I am thrilled it is doing so well. My only complaint is that it soakes up water like a sponge, and I am forever watering it as soon as it shows the first sign of a wilt. I should also mention that I fertilized it twice with Miracle Grow for acid loving plants. I am keeping my fingers crossed that it continues to do well this summer. I hope this helps someone new to growing these beautiful plants as I am.

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A.R.Wadoo February 4, 2010 at 11:28 am

Spring can be tricky for our plant friends, when snow storms attach us in late April even many plants are damaged t physical as wll as phsiological.

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eliz June 8, 2009 at 8:04 pm

I think these special macrophyllas are never going to be completely successful up here. I protect mine with shrub coat, but I honestly don’t know what difference it makes.

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Donalyn June 2, 2009 at 9:49 am

We had much the same results here Kathy – this has been a spectacular year for lilacs and the freezes didn’t faze them a bit. Our entire property is still littered with little “burned” tips of choke cherry and ash branches. I am not expecting my astibles to bloom because of how damaged the ends are and I will have to cut off some hosta leaves, but other than that, so far everthing looks fine. We covered the veggies with planks and straw, and I brought in all of the annuals, but I didn’t cover anything else. Daylilies can typically deal with a frost, but we will have to see if the blooms suffer. On the plus side all the bamboo was killed back nearly to the ground – coming back now but it will not get nearly as bothersome this year. Sumac also is just stating to leaf out again – some people don’t like sumac, but I think it’s pretty so we just confine it to a few spots. We will have to comapre notes later on to see how things do the rest of the season.

Donalyn’s last blog post..Checking In

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Les June 1, 2009 at 8:29 pm

My sympathy and empathy to you. After being in the business for more time than I care to remember, I know which plants we have to watch out for in the spring. March is our bad month but sometimes early April can be surprising. What to drag in or cover, what to leave out always the burning questions in changing weather.

Les’s last blog post..Currituck Garden Tour – Part II

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Helen June 1, 2009 at 4:45 pm

Kathy, These are dramatic illustrations of dramatic weather conditions. But even the long, too-cool spring has had a negative impact in my USDA Zone 5 garden. Tender perennials such as coleus, for instance, seem in a state of arrested time-warp. One of them hasn’t moved an inch since planting a couple of weeks ago. I’d have been wiser to keep it indoors. However, who knew? This has been a wacky spring (frost warnings overnight last night in the greater Toronto region; the morning of June 1st!).

Sorry about your hydrangea. Hope it rebounds for you.

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Mr. McGregor's Daughter June 1, 2009 at 3:47 pm

This is all so fascinating! I can’t believe how dramatic a change the Hydrangea undergoes. I tried to protect some of the buds of my Cladrastis kentukea, but they still got zapped. The weird thing is that some unprotected buds appear to be ok. It will be interesting to see if it blooms at all this year.

Mr. McGregor’s Daughter’s last blog post..A Grand Day Out at the Chicago Botanic Garden Part I

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Annie in Austin June 1, 2009 at 2:58 pm

Wow! Those before and afters of Hydrangea and Columbine are very dramatic, Kathy.

Some of my worst cold damage this year didn’t come from cold air, but from the hail storm at the end of March. The damage didn’t show up right away either, but in addition to leaf & branch breakage or chipping, many plants turned out to resent having a couple of inches of hailstones sitting on them for several hours. Some showed freeze damage or stopped growing for weeks, others died quickly. It’s surprising how some plants can look so frail and be so tough.

Annie at the Transplantable Rose

Annie in Austin’s last blog post..Garden Bloggers Bloom Day, May 2009

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