What happens to plants after an untimely freeze? Part 1

– Posted in: FAQ, Weather

Part of what makes my cold climate garden cold is the fact that we live in the bottom of a valley, and cold air flows downhill and settles all around us. So however cold the weatherman predicts it will get, it’s usually colder here. Often, ten degrees colder.Temperature recorded on May 19, 2009 For example, on May 12th, when a light frost was predicted, the low temp in the morning was 28F(-2C). The following morning, it was 28.5F (-1.9C). I call those two hard frosts. And on the 19th, it was 25.5F(-3.6C). When it gets that low, I call it a freeze. And I believe all these recordings were on the high side, because the temperature sensor is located near the house, under an overhang (it’s not supposed to get sopping wet), in the general neighborhood of where we are raising a bunch of chicks, using two heat lamps to keep them warm.

So, what happens when we get an untimely freeze like that? Well, it depends…

Same Genus, Different Species

Trumpet lilies. Missed these for the first frost

Trumpet lilies. Missed these for the first frost

I really don’t know what species or parentage these “trumpet” lilies are, but they are definitely the most frost tender lilies I have. Lilies only put out one set of leaves per year, so these plants are starting the growing season handicapped with less than a full complement of leaves. I don’t expect any blooms from them. I’ll be happy if they make it through another winter, and give me another chance.
Oriental lilies. Covered every time.

Oriental lilies. Covered every time.

When I removed the containers that I had put over these Oriental lilies to protect them from the freeze, I could see frost in between the leaf layers. But a week later, they still don’t look damaged. This surprised me, because I remember them getting damaged by frost in other years.
Lilium henryi on bottom left was never covered, never damaged.

Lilium henryi on bottom left was never covered, never damaged.

I didn’t realize the Lilium henryi bulbs had emerged, so never considered covering them, and they made it through just fine.

Protected in Vain?

Arrow points to dahlia I foolishly planted last week, when the warm weather addled my brain.

Arrow points to dahlia I foolishly planted last week, when the warm weather addled my brain.

Unfortunately, that wasn't enough to protect them from a 24F freeze.

Unfortunately, that wasn't enough to protect them from a 24F freeze.

Plants from tropical climates have their limits when it comes to cold tolerance. Whatever temperature it was inside that upturned flower pot, it was still below freezing. However, keep in mind the insulating properties of soil. As a result of a timely comment, I was inspired by this post to pile more dirt over the tuber after I planted it. This protected it sufficiently that it was able to send up new growth.
A week after the big freeze, the dahlia tuber is putting out new growth.

A week after the big freeze, the dahlia tuber is putting out new growth.

If the tuber itself had frozen, it would have died and no new growth would have been possible. Often in a cold climate, it pays to plant things a little deeper.
These bleeding hearts were also protected, but still suffered damage from the big freeze. I think some flower buds made it through, but bloom will be reduced.

These bleeding hearts were also protected, but still suffered damage from the big freeze. I think some flower buds made it through, but bloom will be reduced.

Sometimes the most you can accomplish is reducing your losses. The more undamaged foliage there is, the more that foliage can feed the roots, building up the plant for a bigger, better display next year.

Continued in Part 2, where I illustrate how appearances can be deceiving, what happens to trees and shrubs, and a few plants unfazed by the dramatic temperature drop.

About the Author

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.

What differentiates a bulb from a perennial plant is that the nourishment for the flower is stored within the bulb itself.…There is something miraculous about the way that a little grenade of dried up tissue can explode into a complete flower.

~Monty Don in The Complete Gardener pp. 142

Comments on this entry are closed.

Leah Bradford January 23, 2014, 6:33 pm

Hello! I have a question about our trees here in Alaska. We are having a very strange winter very warm everything is thawing! . What would happen if our trees started bud leafs and then we freeze again because we are going to freeze again. But….. we are seeing baby green grass along the roads and ditch lines in the country where the snow has melted. Here in Alaska our trees (Birch) in the a normal spring get a reddish color, then a light green tint up high in the branches. Well we have every sign of spring, but here in Alaska we are months away from spring/summer! Can you answer the question for me please? How crazy it would be not to have lush green leafs in the trees. Is that possible? Thank You, Leah Bradford

Kathy Purdy January 23, 2014, 6:42 pm

Leah, I can only guess. It is possible for the trees to put out a second set of leaves after the first set is killed. I have seen this happen. But I suspect that this weakens the trees. If you then have a normal spring and summer, everything will be all right. But then, what if you have a drought in summer? Then you will probably lose some trees, maybe not right away. Maybe they will fall victim to an insect. So there is no definitive answer because no one knows what the future will bring. How odd that you are having unusually warm weather while we are having much colder weather than in recent memory. But then, the last two years were unusually mild, and this is actually more typical.

May R. Vail Lee October 14, 2010, 3:03 am

Hi! Today is 10-13-10 and I just stumbled into your blog because I wanted to read more about dahlias. I live about 20 miles to the border of Canada and Washington State. We have a little bit milder climate but I always dig up my dahlias. Today, I spent it just digging my dahlias. We had a very wet spring, summer and fall that almost all my dahlias did not survive. I moved the patch to this area just to rotate the planting areas. Unfortunately,we had a lot of rain; the ground is a little bit lower and I did not realize that the ground is really clay below even though we had it plowed so many times because we planted corn and squash and cucumbers there before. It kept all the tubers in water and almost everything turned into mush. Now for your spring planting, save your gallon or quart juice and milk containers, take out the cover and cut off the bottom. Dig the hole deep, put your stake, plant your dahlia tubers, cover well halfway then thread through the plastic bottle, pack more soil to anchor the plastic bottle. Do not take the cover until the dahlia leaves are coming out of the top. You will have a head start in your planting and at the same time, avoid having to spend money on the slug bait. Have fun! May

Kathy Purdy October 14, 2010, 9:44 am

Thank you for stopping by and taking the time to comment, May. I will try to remember this dahlia trick next spring. My dahlias didn’t winter over 2009-2010 and I didn’t replace them, partly because I plant them by the porch and the porch was getting torn down and rebuilt. So maybe next year . . .

kerri June 17, 2009, 7:47 am

Kathy, I’m late, but glad I didn’t miss this post. It’s interesting to see the damage you’ve documented. I don’t think our temp was quite as low as yours on the 19th, but that was a doozy of a freeze, wasn’t it? My bleeding hearts were looking glorious, and then ZAP, they were reduced to pale strings of shriveled hearts. The white bush survived almost undamaged though…it’s perhaps a little more sheltered than the pink, but right next to it.
Our Miss Canada (late blooming) lilac seems to have been damaged too (leaves curled under and had brown edges), but it made a comeback and is blooming now.
I do hope those lilies survive that were passed as seed from your grandmother.

kerri’s last blog post..Garden Bloggers’ Bloom Day – June ’09

Dee/reddirtramblings.com June 1, 2009, 6:11 pm

Oh, you poor girl. It is always cooler at my rural home than in the towns I live between, so I understand about the temperature variances. So sorry about the freeze.~~Dee

Dee/reddirtramblings.com’s last blog post..Hangin’ with my Peeps

Mr. McGregor's Daughter June 1, 2009, 3:51 pm

I’m going to make note of the deeper planting for Dahlias. At least that’s going to do something in your garden this year. I’m sorry about all the damage.

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

Elizabeth June 1, 2009, 2:56 pm

So sorry to hear about your hard freeze! Good for you for making it a learning experience for all of us!

Elizabeth’s last blog post..Black Pansies

Annie in Austin June 1, 2009, 2:52 pm

Oh, Kathy – what a shame to lose the lilies. I hope putting on your scientist hat while assessing the damage helps keep it from making you too sad. Sure hope that dahlia keeps growing! Going over to Part II now.

Annie at the Transplantable Rose

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

Kathy Purdy June 1, 2009, 3:08 pm

Annie, the tops of them got damaged, but they still have some lower leaves. I’m going to nurse them along and hope they come back next year, because they are the lilies I grew from seed my grandmother gave me.