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Frost Damage On Fruit Trees – Critical Temperatures Chart

Frost damage to your fruit tree’s tender buds and blossoms! It’s a risk that many of us realize during Spring when temperatures can swing wildly. Do you want to know what temperatures will frost damage your blooming fruit trees?

Hint: It’s not as bad as you might think. They can survive (usually). Depending…

I have a few young apple trees that got severe frost damage a few years ago during the Spring. This resulted in zero harvest. The apple blooms were doing great… and then a sudden weather change one night. Plummeting temperatures down into the teens. And that was the end of that.

I just had someone here on the blog refer to an excellent chart sourced from Utah State University – Extension website. “Critical Temperatures for Frost Damage on Fruit Trees”.

There are great reference pictures of the fruit tree buds & blossoms in different stages of development – versus critical temperatures. This helps to closely visualize and compare with your own fruit trees state of development (buds / blossoms).

Hat tip to ‘Minerjim’ who alerted us to the chart. He also said, “Depending on the type of fruit, and the stage of blossoming, buds can survive down well below freezing very well.”

Thought this might be helpful to those of you that are facing colder (freezing) temps this spring that you are not normally used to.

The following table was first developed by Washington State University.

It lists Fahrenheit temperatures for each stage of development at which 10% and 90% bud kill occurs after 30 minutes exposure.

For example, in the chart below for Apple trees…

If your apple buds are in the early “Green Tip” stage, you might only get a 10% loss if temperatures hit 18 degrees F.

However, if the apple blossoms are in “First Pink” stage, you might lose 10% at 28 degrees F. But you may lose 90% of them if temperatures drop to 24 degrees F!!

So, it depends.

I just took the photo (up top of this post) of my McIntosh apple tree. It shows buds in the Green Tip stage – actually just pushing beyond it. Today is April 21. It gets riskier as those buds go further into bloom, especially full bloom. That’s when it seems to happen up here… Mother Nature playing tricks. We’ll see what happens this year.

Apple Tree > Bud – Blossom Frost Damage Temperatures

Pear Tree > Bud – Blossom Frost Damage Temperatures

Apricot Tree > Bud – Blossom Frost Damage Temperatures

Cherry Tree > Bud- Blossom Frost Damage Temperatures

Peach & Nectarine > Bud – Blossom Frost Damage Temperatures

(Here’s the PDF from USU.edu)

(UPDATE)
So, I posted this article yesterday. I obviously JINXED myself. Today, April 22, I woke up to this:

23 Degrees! And 3 inches of snow! At the end of April? Uh-oh…

Referring to the critical temperature chart for my apple trees, it looks like (in theory) will have lost about 10%, since the buds are closer to the “half inch green”. Oh well. This is what happens…

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16 Comments

  1. I always just assume safe down to 25 (solid freeze) until the fruit has set. Once fruit has set they can survive a lot more. At least, that’s my experience.

    I also think humidity makes a difference.

    I have an almond tree that doesn’t bloom all at once–it blooms for about three weeks. Right now it’s in full bloom and the fruit has set for the first blooms. If we had a solid freeze tonight, we’d still get a harvest.

  2. In 1895, pioneers planted 30 acres of apples in our little valley. In the 40’s, ranchers acquired the property and cut down most of the trees for better pasture. In 1970, 5 acres of apple trees were replanted (about 300) by my husband and his brothers.

    We have a unique microclimate in which apples thrive, however there are those late frosts and freezes that determine the size of the apple harvest in the fall.

    Almost like clockwork, the trees bloom in mid April. One of the artifacts left behind from the apple heyday were smudge pots. They have a 2 gallon capacity with a 2.5’ chimney. I assume they used motor oil or kerosene. The smoke would blanket the little valley and prevent frost damage.

    So many times we would have loved to use them when a cold night was in the forecast, but we were too chicken to try it without EPA permission (which I’m pretty sure we’d never get).

    Our rule of thumb has been 28 degrees. Above that temp there is very little loss even when the trees are in first bloom. If the temp is below 28, then bloom stage, humidity, and duration determine the extent of damage.

    The bees are here, forecasts look good, could use a little more rain, hoping for a great harvest this year.

  3. Thanks for the info! All of my young apple trees, cherry trees made it through first year. Peaches and pears….not so happy. Getting ready to put in some replacements. Right now they are out in sun during day, and sheltered in garage at night. Will wait a few more weeks before putting in the ground! My high desert is COLD.

  4. I just updated my article with a new picture. This is what I woke up to this morning. And, 23 degree temperature! Jinx!

    1. Ken,
      You losses may not be that bad. If the blossoms got coated with a bit of water before freezing, they might be encased in a thin shell of ice. This tends to hold them at 32f, and safe. Actually, under the right conditions, spraying water on blossoming trees to give them a shell of ice is a strategy to prevent frost damage.

      1. Minerjim,

        I used that strategy once in Wisconsin, when we had a late frost. A fine mist after dusk seemed to do the trick. We had fruit when others didn’t. Another grower shared that he used the old Christmas lights, the big bulb kind, strung throughout his fruit trees. They generated just enough heat to provide some protection. I’ve never tried that one, but if it works, it would also be festive!

        1. Farmgirl,
          You either mist and put ice on the blossoms, or try to keep the temps up around the blossoms with heat. I have too many trees in my orchard (15) for electric lights. that’s why i hang coleman lanterns in them, which put out a bit of heat. It helps that i collect Coleman lanterns, 20 or so that are in great working order. Of course the neighbors think i am crazy, but that’s nothing new. When the trees are in full bloom, the orchard lit up in the dead of night is actually quite beautiful.

          1. Sounds like it would be. I just thought of another one, definitely weird, but might work if it’s critical. Overnight, neighborhood bar-b-que. ;-)

    2. It was 24 degrees in Unity, problem is that it was at that temp for an extended period of time, i would expect way more than 10% loss

  5. The last property I had, before Lightening Point, we had 52 Fruit Trees, it was ALWAYS a Hit and Miss around here. One year would go so bountiful we would need to pick 1/2 off to keep the limbs from breaking, other years…. NADA

    Good Info Ken… BTW When we would have a frost late, it was not uncommon for us to be out with Water Hoses to water the Trees Blooms (entire tree) to form a ice shield over the bud. This would keep the colder air from getting to the buds. Seemed to work more often than not…..

  6. There is a product, organic, called Frost Shield ( made by Maz-zee company in Cal.) that will put a coating on blossoms to prevent them from desicating in a frost down to 26F. I was given some, but have not used it. It might be something to look into for those of you who are faced with temps just dropping below freezing. The label says it lasts for up to a couple of weeks, application rate is like 2 qts/ acre, so it goes a long way. there are others on the big A that are organic as well. Be sure to use Ken’s link to get there.

  7. In eastern WA large acreage farms use wind machines, especially in orchards with more frost-vulnerable fruit. The science behind how that works is here: orchard-rite.com/wind-machines#info NOTE – Not promoting this vendor. They just have a good write-up. Wonder if just keeping the air moving helps.

    1. Anony Mee
      Must have worked seen it used on the orchards down here in years past, especially after smudge pots were discontinued.

    2. The idea is to keep the air moving on a small scale some box fans will work for a couple of trees ,good for about a 10degree drop ,,cousin used small airplane engines and propellers to protect his citrus groves,he also sprayed water to hold the freeze out of the trees

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