What does everyone consider the temperature that kills peach flower buds?
I had -12 to -15 F in my mind, but then I was looking for some reference to back me up on that and I found some stuff saying about -20 C (so -4F).
There is this old publication: Cold Resistance of Stone Fruit Flower Buds
Levers,
As you point out, hardiness can be pretty variable. I appreciate the article you linked.
They claim a minimum hardiness level for the buds is -5F, but peach buds gain hardiness when there are extended cold temperatures which are below 27F for the daily high temperature. They claim peaches gain a couple degrees of hardiness for each day the the fruit buds remain frozen before the test event.
In other words, they are saying the T50 (50% of the fruit buds are killed) starts at -5F but goes lower by 2 degrees for each day the high is less than 27F, but then loose hardiness very quickly when the temperatures rise above freezing for even a short period of time.
I’d say that’s probably pretty close to right. I’ve never gotten winter damage to fruit buds as long as the temps don’t get too much below zero, but have noticed some damage when temps get below about -5F. I’ve noticed heavy damage before when temps got as cold as -9F, and noticed very heavy damage at temps below -11F.
At other times, I’ve also noticed very little damage at -9F, so it’s all extremely variable. I’ve not grown peaches through a -15F temperature yet, but I know some people on the forum have, without losing a peach crop.
Generally speaking I get worried when we get to -10F. I wouldn’t expect a complete loss normally, but would expect some losses.
As the article points out, it doesn’t take much to make a full crop. We lost a lot of our crop last year to spring frosts, but the trees made up a surprising amount of the loss with larger peaches, enough to the point that some trees will still breaking down with fruit. Of course some trees had no fruit.
I think with this cold spell yesterday, most of the Midwest had decent acclimation to the cold, so the buds are probably fairly cold hardy as peach buds go.
Many times it’s not one event which wipes out a peach crop. It’s wave after wave of cold weather, each wave taking a tithe of the crop, till there’s nothing left.
Thanks @Olpea for backing up the data with your experience. Some of the Canadian publications I came across were coming up with -5F for T50 even after significant winter cold.
You are right… there is lots of winter and spring to go. If this last cold snap is an indication, it could mean the polar cold is taking a more westerly path this year, as opposed to the more easterly path it took last year.
Levers,
I all add one more comment that some people have indicated their peach trees have fruited at even colder temps than -15F. Occasionally someone in up north will mention a peach tree which fruited at -20F or colder. I’ll admit it’s hard to believe, but the article you linked did say that -30F was the maximum hardiness for peach fruit buds.
Again I wouldn’t try to give anyone false hope. Generally as you mention -12 to -15F is probably pretty close to the upper end of fruit bud hardiness in most cases (that is anything colder than these temps will result in no fruit) but I think there are isolated exceptions.
I have one variety I’ve been working to propagate for years (Wisconsin Balmer). There was originally a mix up in scion wood from my source and so it’s taken a few years to get it all straightened out, but now it looks like I have about 3 budded trees to trial the peach (if the ten below the other day didn’t kill them). I don’t have any scion wood to share right now, btw. Anyway the lady I got the wood from said her W. Balmer regularly fruits when it gets twenty below.
When I first started growing peaches in southern NY State, temps down to -15F were common in the winter, yet the only winter that destroyed or even significantly damaged my crop had temps down to -22. Last winter had a single night of -12 that destroyed my peach and nect blossoms. I had noticed that the blossoms seemed unusually swollen in the mild weather of last winter that preceded the single very cold night. The trees shuttle water out of the flower bud cells to increase hardiness. Wish there was a chemical that could trick them to do that regardless of temps.
We’ve already had a couple of frigid days that didn’t get up to 27F in the last week. Yesterday was one of them and my hands got so cold while trying to tape some small branches for training purposes (Red Delicious really has a sucky growth habit) I had to go to my truck, start the engine and warm my hands. I was pretty miserable the first couple hours of pruning, but knowing that my peach and nectarine buds are hardening makes it worth it!
Maybe I was dreaming totally misunderstood something I read but I have heard that ice can protect fruit blossoms. Would it be possible to spray a peach tree with water prior to temps reaching -15 in order to create a protective ice barrier to the fruit bud?
I’ve only heard of that being used for spring frosts, but I don’t know.
@speedster1, could you be talking about heat released when water freezes? Spraying citrus with water and allowing ice to form is a way to provide a little protection from cold.
I was hoping for the same. We had a freezing mist that coated everything in a light layer of ice before the big plunge to - 10 and that deep freeze only lasted 12 hrs or so. I am being optimistic that those 2 things may have worked in our favor here.
An ice coating is no protection at all. What protects is the release of heat as water freezes.
A single cold day below 27F high increases cold hardiness of fruit buds. But as soon as the temperature goes above freezing hardiness is lost just as fast.
Ok. That’s where I have no understanding at all of these types of matters. I thought maybe the ice had insulation properties as weird as that sounds.
@alan
@Olpea
@Levers101
I don’t think that we can talk about " bud hardiness" in absolute terms.
There are so many variables that come into play at the time that the low temperature hit that I think it would be more helpful to talk about a “danger zone” of low temps rather than an absolute low temperature number.
Some of the variables I can think of and I am sure others here will be able to come up with more, are:
I am sure that some “non math-challenged” member here can figure out the permutations of just these 7 variables.
For me, I just listen to the Dionne Warwick song ( am I dating myself) … “Just Wishin’ & Hopin’”
https://www.youtube.com/watch?v=cdznyG4cKdA
Mike
It’s not very insulative. In fact, ice has a slightly higher thermal conductivity than water.
Even if ice were a good insulator there is virtually no heat in the flower buds to insulate. It’s not like trying to protect a heat source.
The counter intuitive part to me is the idea that freezing water releases large amounts of heat. So I have to reminder myself that thawing ice requires a large heat input. Therefore forming ice requires the opposite, ie a large heat output, ie surroundings cold enough to pull enough heat out of water so that the water freezes.
I agree that there are many variables. I had a HUGE peach crop this year and we had some pretty cold temps last winter in 5A Maine. As far as temps and peaches go…-10 gets my attention, -15 gets me worried, and -20 puts me on red alert. Timing is everything though. The wild swings of back and forth cold & warmth are probably the most damaging overall…along with spring freezes.
So your saying that the cold week we had in Des Moines (-12) and the 40 degree temps today, means we have no more cold hardiness than if we had no temps lower than 40?
Here is an explanation that makes good sense. It is regards to cherries, but I am sure it is the same process with peaches.
http://extension.oregonstate.edu/wasco/sites/default/files/horticulture/fruit_bud_hardiness.pdf
I haven’t read the research recently, one paper linked above. My understanding is that after peach trees are fully dormant constant below freezing draws water out of the flower buds. That causes the buds to increase in hardiness by 1-2F each day down to a maximum hardiness. But just one thawing event and part or I think all of the increased hardiness is lost.
A constant temp cold enough to freeze water in the operative tissues is required to build and maintain max hardiness. So yes one day at 40F and the buds are back at some lesser hardiness level. And remember buds can warm up above air temp during the day even in winter when the sun is shining.
What were your lows?
Doesn’t it very by variety also? My peach tree had every blossom killed on it a few years ago and othe peach trees in the area bloomed.