Blossom frost tolerance differs among adjacent apple trees?

[Benja]

Just posting to share an observation. My thermometer recorded 25 degrees in the home garden and orchard Saturday night. Most of the apple trees were covered in fully open blossoms and I believe that many of those blossoms were killed. Sunday morning the bright white color of the healthy, living blossoms had been replaced with the cream color of wilted and frost-bitten ones. I downloaded and read the Utah Pests fact sheet entitled "Critical Temperatures for Frost Damage on Fruit Trees" which indicates that I can expect to see a 90% kill rate on the open blossoms. However, I was intrigued to notice that the blossoms on several trees were still as white as before the frost. I haven't noticed this before, so I'm speculating that there might be very slight differences in frost tolerance among apple trees. Maybe some trees have blossoms that wilt slowly after dying - they don't have more tolerance, but are slow to show the damage. I'll know in a few days. Is it a natural characteristic or just nutrition differences...? Hmmm...

For example, a Crimson Crisp and an Enterprise are separated by 10 feet and look quite different the morning after the frost.

Crimson Crisp apple blossoms appear to be unharmed.


An Enterprise 10' away with blossoms that look wilted.


Here is a close up of the Enterprise blossoms.

I didn't see any earlier discussion on this. Have you seen adjacent trees in similar bloom stages respond differently to a frost?

 

[Turkey Creek]

In a simple answer .... Yes

 

[bwoods11]

Is there one tree that seems to better than others in this scenario?

 

[Benja]

Is there one tree that seems to better than others in this scenario?

I'll take another look at them this afternoon and will note with interest which trees fared best. This Crimson Crisp was in a block of 4 trees in an extension area just outside the fenced orchard together with Imperial Gala, Ginger Gold and Enterprise. For some reason, it was the Crimson Crisp vs Enterprise comparison that caught my attention yesterday morning.
I should add that these are young trees and some have never fruited before. The Enterprise had 2 apples last year and the Crimson Crisp had none. I would be thinning them heavily anyway. These are my first-time observations of apple blossoms and late frost.

 

[SmallChunk]

That Enterprise has lots of blossoms that weren't open, so i would think you should still have some take!

 

[Benja]

That Enterprise has lots of blossoms that weren't open, so i would think you should still have some take!

I surely hope so and that's kinda what I expect based on the MSU and USU documents. I'll be watching and learning in the next few weeks. Documenting it here will help me find it in the future.

 

[Benja]

It looks like the Crimson Crisp might have sustained some damage.


Here's what some Crimson Crisp blossoms look like up closer.


But Enterprise looks way worse.


Notice how the burnt, brown edges look same for both trees. I think this indicates that they both got equally frozen/frosted. But Enterprise is drooping limp and Crimson Crisp is standing upright.

 

[Barndog56]

Any difference in mulch layers between the two trees? Or the amount of airflow through each tree with the wind direction you had that night?

There only needs to be a couple degree variation in each tree's microclimate to make a difference.

 

[Charman03]

It’s been so cold here, probably won’t be a great crop year

 

[Benja]

Any difference in mulch layers between the two trees? Or the amount of airflow through each tree with the wind direction you had that night?

There only needs to be a couple degree variation in each tree's microclimate to make a difference.

No, the mulch layer is same. It's in a deep-mulched, Back-to-Eden style garden and orchard with 6" or more of aged wood chips. The trees are the same age and I'm pruning them about the same. Wind direction was from the north and would have hit the Crimson Crisp first. But this system also around to the Southeast during the night, as they commonly do here.
The trees in this area are planted 6' - 8' apart and pruned short like Dave Wilson Nursery Backyard Orchard Culture. 2 plums, 2 peach, 1 pear, 1 nectarine, 1, cherry, and 12 apples are planted in 2 rows. The Crimson Crisp and Enterprise are neighbors planted in diagonally adjacent spots about 10' apart. Of the 12 apples, Golden Russet at the other end of the row was another tree that had quite a few unaffected blossoms.
I checked ten or so wild apple trees nearby and all are fine, no browned edges or wilted blossoms on any of them. They all look better than the Crimson Crisp. Many of those trees are just loaded with blossoms.

 

[Apple Junkie]

Interesting... I'd have the same questions you do Benja. I'd also come to the same conclusion, that some varieties' blossoms are harmed less than others. I'd be curious to see if the wilted blossoms set fruit. Maybe the Enterprise was just in full bloom a day or so ahead of the Crimson Crisp, and dying off naturally. I am taking a stab in the dark on that thought... the real culprit is probably the most obvious - frost. keep us posted, this is new to me.

 

[4wanderingeyes]

In the last week we had night lows between 24-30 the last 5 days. But as of last weekend, none were blossemed.

 

[Benja]

Interesting...I'd be curious to see if the wilted blossoms set fruit. Maybe the Enterprise was just in full bloom a day or so ahead of the Crimson Crisp, and dying off naturally.

Apple Junkie,
That's a good point and your question gave me an idea - I'll tie several with flagging tape to help observe specific blossoms throughout the season. Together with the photos, I might be able to tell whether fruit came from a wilted blossom or from a blossom that was in "First Pink" or "Full Pink" stage during the frost. Nearly all my trees still have 10%+ of these unopened blossoms.

Bloom maturity is a very good explanation. Blossoms are flowers and flowers eventually wilt and turn brown. I really hadn't been paying close attention to - or recording - first blossom dates on individual trees. I think I remember that Gala and Ginger Gold (these are the remaining two adjacent members in this block of 4 trees) bloomed earlier than Enterprise and Crimson Crisp.

I have more than 3 dozen mature wild apple trees in the surrounding woods. A solid dozen are within 50' of the forest edge. These are are all lower by up to 20' of elevation and within 300' of my orchard trees. So far I have observed zero wilting and only found burnt fringes on maybe 5 blossoms. One of these trees seems to be dying; only a few small branches at the bottom have blossoms, but they look fine, too. Other trees appear to be setting up for a precocious year and currently are more white than green.

In a podcast episode last year Advancing Eco Ag mentioned that a cherry orchard on their program fared much better during a bloom-season frost than neighboring orchards. I believe the theory that excellent nutrition helps trees resist insults from pests and weather, but haven't seen it demonstrated. Somebody here, I think it may have been Native Hunter, wrote about the benefits of full-size trees compared to those on dwarfing rootstock. As I see it, my current comparison is mature, full-size, seedling tree + forest soil vs young, dwarf, grafted tree + fallow-until-5-years-ago pasture/field soil. Am I missing something?

 

[Barndog56]

In the last week we had night lows between 24-30 the last 5 days. But as of last weekend, none were blossemed.

I had pears, plums, and apples all just breaking out of tight cluster, so no damage here. Should be blooms everywhere a week from now, along with some 80 degree highs!

 

[H20fwler]

Our fruit trees seem OK from the couple cold snaps.
The chestnuts broke leaf bud early last week and really took a pounding over the cold. Supposed to be warm from here on out so hopefully they come out of it fast.