Proper pruning times ?

[hillbilly]

Clarification:
With proper pruning time I mean the time of year when
the pruning is least harmful to the tree.

This disussion started in "Winter work or lack of"
http://www.arboristsite.com/showthread.php?threadid=6939

I was surprised to hear people say that late winter would be
the best time.
In the books I've read, the arborists here I've talked to and my
mentor all say that late summer, July, August and September is
the best time for pruning. Second best time would be late winter
early spring.
The impact on the tree as a function of when it is
pruned may vary a bit depending on the tree and the kind of
pruning done, but basically the JAS-period would be the best.

Any input is appreciated, especially if you can back your claims
up with facts (references to litterature of knowledgable writers).

Best regards / hillbilly

 

[John Paul Sanborn]

I agree in general, but pathogen activity, drought stress and other things can come into play there. I have alos notice some bark slipage when some trees are puting on late wood, Gleditsia comes to mide off the top of my head.

 

[TREETX]

"when is the best time to prune my trees and how much will it cost?"

Answer: it will cost X dollars and a good time to do it is when you have X dollars.

 

[FBerkel]

Timing os Summer pruning

Hillbilly,

Here are some quotes relating to late summer vs. early summer. (All of these sources stress that late Winter is superior to summer in most cases; and all agree that fall and leaf-forming are not healthy times).

Shigo, pg 145, Modern Arboriculture:

"wounds inflicted ....after the growing period will have a large area of cambial dieback".

Shigo, Tree Pruning, pg. 31:

"The best time to prune most trees are (sic) during the late dormant season and immediately after leaves have matured"

Shigo also says, in his talks, that summer pruning should be done soon after the first flush of growth, i.e., late Spring/early summer (point 3 on his phenology curve, pg 271). His reasoning, I believe, is that there will be less loss of stored energy, and a greater chance to recoup any loss of potential energy (sunlight that would have been caught by leaves no longer present) by putting out a second flush of growth before mid summer.

When do trees stop growing in Sweden? Here, the second flush of growth is usually over by mid July or so.

Gilman,Pruning, 1'st ed., fage 39:

"Late summer pruning may stimulate an additional flush of growth on species that flush several times a year. These shoots may be damaged by early frost."

P.P. Perone, 6'th ed., 1988, pg. 123 (yes, he's dated on much of his other material):

"Pruning in late summer is also undesirable because it interferes with food storage necessary for growth in the following spring and slows root production."

Harris,Arboriculture, 1983 ed., pg. 386:

"Summer wounds, however, callused much less than spring wounds during the current growing season, because they had less time to."

Harris also suggests pruning in early, rather than late, summer for puposes of controlling tree size.

JPS mentioned drought as a consideration, and that's very im-portant here. I've seen heavy pruning in late summer lead to death within a season.

I'd like to hear the reasoning behind timing pruning for late summer? I'm not saying I'm necessarily right, but I'd need to see your sources to be convinced otherwise.

 

[hillbilly]

Thank you for a very informative post Fred,
that's exactly the kind I was hoping for !

Shigo, Tree Pruning, pg. 31:
"The best time to prune most trees are (sic) during
the late dormant season and immediately after leaves have matured"

I must have been half asleep when I read that page, probably
cause the headline is "No set angle for a proper cut"
-yeah, yeah I know that already, *skip*

Shigo, pg 145, Modern Arboriculture:
"wounds inflicted in the fall after the growing period
will have a large area of cambial dieback".
-I always interpreted this as fall as in leaves start to fall,
that would be late September or even later overhere.

When do trees stop growing in Sweden?
When we cut them down
Seriously, I'd say late July.
If you combine this with the above statement by Shigo, then
August and September would be less suited for pruning, I agree.

JPS mentioned drought as a consideration
If you by this mean very dry summers, this often ain't a problem
here in Stockholm, it rains a lot during the summers.

My other references would be arborists I've worked with as
well as my mentor. Them are just mouth to mouth references
and worth next to nothing in this discussion, they may
however explain how I came to my viewpoint.

Also, the only foreign tree books I have are the Shigo books,
which I had to import myself since they are not available in
Sweden.
I have some Swedish books by "Klaus Vollbrecht", he is probably
the most highly respected arborist in the country and he arranges
many seminars.
In his book "Nya beskärningsboken" - "The new pruning book"
he says "From a biological standpoint all pruning should be performed
during July, August, September.
Stonefruit trees (correct word?), plum, cherry, peach run a big risk of
getting the "gumflow" desease if pruned other times of year.
Bleeders, birch, maple, etc. bleed more if pruned other times.
Extremly sensitive trees like horse chesnut, shouldn't be pruned other times either."


I'm gonna have to discuss this with some people here, I admit my arguments are mainly
of the form "what others taught me", fortunately I am only happy to learn,
that's why I'm still an apprentice

Best regards / hillbilly

 

[Stumper]

When all the factors are weighed and carefully evaluated proper pruning techniques are going to come out on top of season as far as importance is concerned. Yes , Birch and Maples are prone to high sap flows if pruned in late winter-early spring. No less an authority than Dr. Shigo rates this as relatively unimportant to a healthy tree though it can be unsightly. I don't know about your situation regarding "gumflow" disease of stone fruits in Sweden. Heavy pruning in late summer can indeed iniate a growth flush that is susceptable to freezing but HEAVY pruning is generally a bad thing in any circumstance. If it must be done find a better time than late summer.....Like the dormant period. Woundwood formation will take place in spring if it hasn't already initialized during warm periods during the dormant season. From a practical standpoint of keeping tree care professionals in business to provide the service Treetx is correct-When the customer has the money to pay. OR, as 1 author of a pruning manual wrote "whenever your tools are sharp and you are ready to work."

 

[FBerkel]

Hillbilly,

I think everyone on this site is still an apprentice, as we all are eager to learn, or wouldn't be here. And I have to admit, I was a little selective in my quotes (Harris also gives some reasons for pruning late.)

I don't think we're worlds apart on summer timing. I usually prune to Aug., sometimes early, sometimes late, depending on how many jobs we've booked for that season. As the season progresses, we try to lighten the dose, for all the reasons noted. By stopping in early Aug. or so, there's a tremendous oportunity to book Winter work, and at the same time, maybe marginally help the trees' health by waiting for a better season.

 

[John Paul Sanborn]

I seem to remember someone talking about pruning in august

 

[FBerkel]

Two words: evil twin

 

[John Paul Sanborn]

Tom D. says that a lot; "those were the Evil Tom days" or "I could feel Evil Tom coming out".