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Ascertaining Dormancy

Posted by Brittany Kordick 
Ascertaining Dormancy
January 05, 2021 05:12PM
More than usual, we are chomping at the bit to get pruning this year. A particularly horrendous fireblight season, coupled with extensive damage from 17-year periodical cicadas means our dormant pruning will be more crucial and more challenging than usual . . . and since it's just two of us nutjobs pruning 18 acres of M111 trees (only 10 acres in full production, so there is that), the odds are also even less in our favor than usual. We need to get started as soon as humanly possible.

Now, being that we're in North Carolina and it takes longer for our trees to become dormant in the winter, we are accustomed to beginning to prune late January/early February every year. But as our trees get older and larger, and our bloomtime typically begins the last week of March/first week of April, we are increasingly feeling the need to begin pruning earlier. Many of our large-acre conventional orchard regional neighbors must resort to beginning their pruning by Thanksgiving, before trees are fully dormant, in order to get it all done. Even knowing better, one of us was tempted to join their ranks this year. However, we have had a relatively mild winter thus far, and our trees have not demonstrably achieved dormancy yet that we can tell.

We traveled to a customer's home orchard 30 minutes southwest of us last weekend to advise him in some pruning questions (he had begun his dormant pruning already), and we agreed that even more so than our orchard (slightly cooler, higher altitude), his was certainly not dormant. The "evidence:" semi-green leaves hanging on in the highest point of the canopy to the extent that you would have to break them off to remove them and areas of minor new leaf growth, particularly below a branch break or deer nibble.

We've hit the books and research regarding dormancy, chilling hours, etc., and we still have a couple of questions. Number one: is there a way to definitively ascertain dormancy in an apple tree besides "it looks like it's dormant; it feels like it's dormant; it quacks like it's dormant," ergo, we can begin pruning and assume the tree will not react in a non-dormant fashion? I'm envisioning something along the lines of making a light pruning cut and divining something from the appearance of the cambial layer, etc., but have never heard of any such technique.

Question number two: being that we typically have an extensive and quite unseasonable January and/or February "thaw," when temperatures soar for a week or more and make us very, very nervous, and being that it seems like our trees break dormancy earlier and earlier every year (though, amazingly, remain fairly consistent in reaching bloomtime by last week of March to first week of April, no fluctuation beyond that), can we be somewhat comforted by the fact that our trees are apparently taking so long to reach dormancy this winter? By that, I mean, there is scant possibility that they will have accumulated enough chilling hours by, say, February, for us to reasonably fear excessively early budbreak (though, we probably would anyway, just out of habit), correct?

What thinkest ye, fellows? And thank you for thinking on this.

-Brittany Kordick

Kordick Family Farm
Westfield, NC
Zone 7a
Re: Ascertaining Dormancy
January 15, 2021 07:12PM
Hi Brittany,

I don't have a ton of time to chime in, but want to do so in some capacity this morning.

To take a stab at your questions:
1.) How can you identify dormancy? This is tough in our climate, because an apple tree tends to not go dormant all at once. I honestly don't think an apple tree views itself as one entity, with each new year of growth acting independently of the rest. And slowly my management practices are heading down that road of treating one tree as more than one. I'm reminded of this in late fall, where a new flush of growth happens at the very highest branches, while the scaffolding branches have lost all leaves of their own volition and are tucking in for winter. Vigor is to blame, and often too severe of dormant pruning *coupled* with too little of summer pruning is a reason for the tree not heading into more appropriate dormancy in my mind. (Note: I used to be against summer pruning because of fireblight. That opinion has changed).

2.) Chill hours are correlated with dormancy and bud break. So, yes, I think you're right in assuming that you'll be better off escaping early break. But this is a double edged sword because delayed bud break puts you firmly into insane fireblight risk. I've noticed that the trees whose leaves I don't strip most often get blossom blight, where the others get twig blight. I'd much rather deal with twig blight than blossom blight, mostly because I'm not "on it" when it comes to fireblight and spraying the blossoms isn't something I enjoy doing at 4am.

Hope this helps in some capacity. I would look towards research on African countries growing apples for better light on chill hours, management, etc. Good luck!

Re: Ascertaining Dormancy
January 16, 2021 04:02AM
Thanks, Eliza. That really helps to better frame our thinking on this subject, and as always, it's just nice to know we're not alone. I can imagine it must be strange for Northerners to hear from a fellow apple grower anything along the lines of: "It's January in the Western hemisphere; do you know if your apple trees are dormant?" Give it a few decades, your time may come . . .

We felt the same way about summer pruning, limiting ourselves to cutting out shoot blight strikes and cutting back root sprouts, but are also slowly coming around to the virtues of more intensive summer pruning, not least because it may lighten the load a bit where dormant pruning is concerned, and we never manage to get it all done anyway. I think your point linking vigor to dormancy is spot-on -- we do often have a lot of cases of heavy dormant pruning/heavy vigor the following season because we've had to skip a year pruning a variety that we just couldn't get to, then whack it extra hard to make up the following year.

Kordick Family Farm
Westfield, NC
Zone 7a

Edited 1 time(s). Last edit at 01/16/2021 04:04AM by Brittany Kordick.
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