“When the pruners are sharp” is the old orchard person’s cliché. Of course, the literature suggests dormant pruning is less growth dwarfing than pruning after first growth… but I do wonder- at what point do the growing leaves start to take and then contribute energy to the tree at large. At first they are mostly? entirely? running on stored energy from the immediate vicinity of that growth- roots and leaves alike, so how does pruning affect the remaining tree’s energy bank account? Once leaves show green, presumably they are producing carbs… but where do those first carbs go? Undoubtedly depends on species and season, but it does bring to question when is the best time to prune fruit trees for most rapid establishment and then when it is the best time for the development of fruit… size and taste (brix).for established trees.
It’s easier to see what you are doing once established trees clearly show their flower buds and I can’t really see a down side if you wait to prune until then, or when trees are fully in bloom, or even after fruit is set.
I’m just starting a discussion here.
I already know that peaches are often recommended to prune after first growth to reduce likelihood of canker- double so for sweet cherries for which I do most of my pruning right after harvest.
Has any research been done on pruning pears only in mid-summer when it’s too hot for fire blight to spread?
I’m a fan of dormant pruning because of several factors:
For starters when the tree wakes up it is hormonally pumped for growth. This is not limited to pushing branches but also for pushing healing; the faster the tree heals the less likely it will catch a disease or insects may decide to start boring.
Even without boring, insects are a vector for disease just by moving from tree to tree, carrying spores and viruses. Dormant pruning minimizes the window where the tree skin is off.
When you prune while the tree is dormant the tree doesn’t even seem to notice was just happened, it just wakes up and goes on with it’s business. Pruning a tree that is awake can shock and confuse the tree. The tree can start crazy growth in order to overcome the injury which interferes with the normal seasonal cycle.
Also i think it is better to avoid it when the tree should be busy spending energy doing something else, from pushing flowers to growing fruit to getting ready for dormancy. Healing is metabolically taxing and the less taxed your tree is the more it can focus on growing and staying healthy.
Sounds like an excellent argument for waiting past dormancy to prune as do your other suggestions.
I have noticed a strong tendency of people to anthropomorphize plant reactions to physical injury, but I figure pain serves a purpose and a stationary plant would not be served by this very energy expensive process of sustaining a brain that delivers pain signals via a nervous system connected to a brain. Not much they can do but take it, you know :
Alex Shigo suggests that the only bad time to prune is when trees are in the fall schedule of hardening off for winter, however commercial orchards around here sometimes regularly prune their huge orchards immediately following harvest with no apparent negative consequences to these bearing age trees.
Most of the energy involved in dormant pruning is what’s stored in what’s removed. Until a tree begins delivering carbs through newly formed leaves, waiting for first growth to prune shouldn’t really have any consequence at all. Wound healing begins when growth begins, which is why guidelines often recommend pruning peach trees sometime around bloom so the wounds heal shortly after any exposure to infection. Dormant pruning increases the risk.
Any energy already stored in the roots is unaffected by pruning, but pruning could affect the amount of energy stored by the roots in one way or another, I suppose, given that any leaves in more than about 70% shade are an energy sink, so eliminating shaded wood could theoretically lead to more energy storage, some of which might end up in the roots. However, any fruit tree properly pruned will likely suffer from a diminished amount of overall energy production. Consider another orchard keeper’s adage, “a pruned tree should be open enough to throw a cat through it”. Light that reaches the ground is light unharvested by the tree, obviously. A “properly” pruned fruit tree leaves lots of patches of light on the ground beneath until new growth closes it off. That’s when I generally summer prune.
It doesn’t have to do with that but with the fact that when the plant is leaving dormancy the hormonal signaling in the plant is set in a condition ideal for growth and repair.
Just like with people (without the intent to anthropomorphize here) systemic functions are regulated by hormonal signals. At the specific time of waking up from dormancy the plant system is pumped for woody cell growth which are more conductive to healing. Obviously these are present throughout the season but are just at their most effective at this point.
Heck to be honest I don’t do late pruning because my last frost is in late May and my first hard frost starts in early October, a full six month season is a good season for us. The plants can use any advantage I can give them.
So which is it… either you are a fan of pruning trees when they are dormant or…
I like to prune apple trees once they’ve started growing because I like seeing how full of flower buds a tree is and I might adjust pruning accordingly. For peaches that goes double- sometimes the only peach flowers to survive winter are on the weakest twigs which I would otherwise remove. I also like mid-spring and summer pruning to increase airflow and get sun where I want it- to leaves that send energy primarily to developing fruit and next years flower buds. I like pruning established apple trees all summer long so I have less dormant pruning to do, which always keeps me too busy from mid-Dec through March. I stop summer pruning peaches by Sept because of fear of interfering with the hardening off process, which isn’t an issue here with apples which I sometimes prune into Oct.
Pruning fruit trees is half my business and if I didn’t utilizes all windows I could not manage all the orchards I do. Fortunately the trees just don’t seem very picky about it in my climate. These days winter never seems to go below -10 and summers rarely exceed the 90’s.
Although “energy” is a common metaphor for plant processes, it is not a good one – nor is “stored in the roots”.
With fruit trees, a better metaphor is to consider:
the life center of the plant is below the soil line
everything above the soil line is sex and solar panels
For deciduous trees (BTW there are summer deciduous trees) the activity above ground takes a break but below ground there are active processes occurring in the roots. So “storage” is not really happening, instead proteins and enzymes are being manufactured – and towards the end of dormancy hormones as well.
In several U.S. locations, winter is the best time for pruning of vigorous deciduous trees. (Sometimes I wonder about the connection between “pruning” and “Prunus”). Additional summer pruning can also be beneficial, esp. when training for size. But there are regions in the U.S. (e.g. SF bay area) where the presence of disease overrides winter pruning. Many an apricot and plum has died because of it.
“We demonstrate that storage is actively accumulated, as part of a conservative, bet-hedging life history strategy. Storage accumulates at the expense of growth both within and across species. Within the species Populus trichocarpa, genetic trade-offs show that for each additional unit of wood area growth (in cm2 yr−1) that genotypes invest in, they lose 1.2 to 1.7 units (mg g−1 NSC) of storage. Across species, for each additional unit of area growth (in cm2 yr−1), trees, on average, reduce their storage by 9.5% in stems and 10.4% in roots.”
This behavior is similar to that described in deciduous fruit trees, which accumulate carbohydrate reserves before leaf fall and utilize them during the dormant season and the spring growth (Schaffer et al., 1999). In deciduous trees, the root system is the major storage organ for carbohydrates
That’s just a quick search. Are these concepts obsolete? If so I will be grateful for enlightenment via links to research.
You seem to have misunderstood my statement twice. You prune when they are dormant so when the tree wakes up the tree goes to town fixing the injuries.
It seems as though your are saying the two scientific papers I quoted are wrong, but you haven’t provided any evidence that you are right.
This isn’t helpful to me or probably to anyone else trying to understand the question of root storage of carbohydrates. If you are going to contradict me, at least go to the trouble of finding a piece of literature that supports your contentions, for the forum. One of the articles said the carbohydrates were used to stimulate spring growth, how is that stimulation created without the expenditure of energy- that is what the carbs are used for, unless I’m missing something that I cannot find an explanation for in your text.
This discussion is going poorly. The trees cannot go to town until they start growing so what is the difference if you prune them then- for peaches it is routinely considered more beneficial to prune them when they are well into growth because that is when they close wounds fastest and it is supposed to reduce the risk of canker infections.
What’s more, with all the dormant pruning I do, I’ve never seen any consequences of pruning in the middle of winter when compared to early spring. Shigo spent his life researching response to pruning wounds and the only time he found that healing was delayed was fall pruning. Only that healing was meaningfully delayed, not that trees suffered from it.
I have to look this up. I remember something about late summer pruning to encourage fruit spur formation. I tried it last year but haven’t evaluated the results.
Two things I remember from discussions here: pruning pomes before the summer solstice ecourages spur growth, and late summer pruning (to the third leaf) of new growth often results in spurs just behind the cut.
I can’t speak from experience to the former, but the latter seems to be working for me after one trial.
I checked but I don’t think so. If you mean Carl Linnaeus, he was from 18 century. Both meanings (originating from latin and old french) of prune (fruit) and prune (cut or round off)) have etymologies predating Linnaeus.
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