Hope you enjoy this article from Good Fruit Grower.
Here is a link that might be useful: Article
What amazes me after reading that is that we don't have more freeze injury here. In TX and Kansas it can drop 60F in a matter of hours. I once saw it go from 96F to 30F in 36 hrs in Amarillo. And that 30F was the only September freeze ever when it happened. In winter 50-60F change in a week isn't rare, it's the norm.
Fruitnut, the big damage is sudden drops well below freezing. If you read the article, one of the sudden drops that started high and ended a little below freezing did no important damage except to Granny Smith fruit. All the tree damage occurred in freezes at least 15 degrees lower than that when trees weren't hardened off.
That type of stuff rarely happens here in southwest Wisconsin. We just don't get warm wx in winter. The snowcover is usually sufficient to hold temps in check, even with warm air close by to the south. I think the last time we were 40F or warmer was late December.
from the article:
"The best temperature range for preparing a tree for the winter is between 30 and 50 degrees, Smith said."
We get a ton of hours in that temp range in the fall here.
"Any warm spells in January or laterÃ¯Â¿Â½anything above 40 to 42Ã¯Â¿Â½FÃ¯Â¿Â½will begin to bring the tree out of dormancy. On January 16 this year, the temperature in Wenatchee climbed above 50Ã¯Â¿Â½F. Smith said this would count in terms of the treeÃ¯Â¿Â½s dehardening process but the warm spell was not long enough to make the trees particularly vulnerable to cold"
It never really warms here until March, although one winter we NEVER went below 0F until early March...but it was only -5F or something like that...
"Since thereÃ¯Â¿Â½s no way to control the weather, growers should keep in mind that the more vigorous the tree is growing in the fall, the more vulnerable it is to early cold spells. To protect a tree from mid-winter cold injury, wrap the trunk to prevent sun damage, and make sure that the soil is moist going into the winter to avoid root damage. "
I think the biggest asset we have here in Wisconsin is heavy snow cover. It really helps keep the trees dormant well into spring. I know one year i was throwing shaded snow around my Peach trees (that were snow free by that time) to keep the roots chilled, so the tree wouldn't flower too early. I should be doing it with apricots, since they want to flower as sun as the snow is gone.
Great article, thanks for sharing. My biggest concerns growing sensitive fruit here (peaches/sweet cherries) are max low temps (-25F or colder) and late spring freezes...
The article states, "One of WashingtonÃ¯Â¿Â½s great cold snaps of all time came in 1955, the temperature in Wenatchee dropped from 56Ã¯Â¿Â½F to 11Ã¯Â¿Â½F within two days in mid-November and continued to drop over the next couple of days. Growers reported hearing snapping and popping as tree trunks split at night.... Cherry trees suffered the most, and apples more than pears. Half a million trees were lost."
Like Fruitnut, I'm a bit surprised Washington gets such massive freeze damage from fluctuating temps. While I haven't recorded anything, it doesn't seem unusual for KS to go from 56F to 11F w/in 48 hrs. in Nov. It must be trees harden off later in the season in WA.
Of the temperate fruits, we get winter injury on blackberries and fall planted peach trees, but not much else.
Also interesting the article states Southwest injury is caused by sunshine de-hardening the trunk. I always heard it was caused by the freeze/thaw of water in the cambium. Wonder which it is?
Any comments on the validity of this statement "By the end of December, a tree is usually as cold tolerant as it is going to get. The tree can lose hardiness from this point but not gain it." ?
How about regaining hardiness lost after a short period of thaw?
I was in Wenatchee on Tuesday of last week where essentially Tim Smith gave the same talk for the "Apple Day" as he did for this talk on Thursday's (?) "Stone Fruit Day".....it was received with interest by the growers.
Tim Smith is very knowledgeable and I am glad that he told me last week he has no intention of retiring any time soon.
A few notes:
1. Keep in mind that Washington grows a lot of stone fruits.....I saw little of that when I was in Wisconsin and I rather doubt Kansas has that.....some of what Tim is talking about here is for stone fruit.
2. I personally have not seen that much winter damage to fruit trees either in eastern or Western washington....but I am quite sure it happens....ESPECIALLY in the outlying areas (like Methow valley) where the temperatures may really act like an Arctic freeze hit them.
3. Tim does not expect much damage to the apple trees this year in Washington, .....only to the very new cherry trees in selected areas. Keep in mind also that Tim was talking to Eastern Washington large fruit growers.....not to hobby growers with houses and homes who may have a much warmer micro-climate next to their house.
4. I asked Tim if I could prune trees now if the temperature was below 32 degrees and he certainly thought so....if I can "stand" to be out there, so can the tree stand to be pruned, he said.
5. At this meeting last week in Wenatchee, there was a talk given about the Brown Marmorated Stink Bug....we do NOT have the problem here but we are watching what is happening to you on the East Coast and we believe it is only a matter of time before we do.
This winter has been much better than last winter for temperature fluctuations. Our worst day so far is 70/17 on the same day. Last winter we had many days like that and worse. There's a reason WA has a vibrant fruit industry while this part of the world has a few hardy home growers and small commercial operations. Their weather is vastly better than ours. It's just that WA can get a severe freeze once every 10-20 years. The economic impact is severe when that happens.
We've got the right temperatures, climate and source of water (the Colombia River) to make for the best redness, typiness and production....
Yesterday's Seattle Times article confirms that after struggling the past few years this past year has finally given fruit growers a much needed lift here....and if anything, Washington apples have increased their dominance.
But I stray too far from the topic.