you might get better answer in the conifer forum on the GG ... but those peeps visit here... so it doesnt matter this time...

but do keep in mind.. part of your inability to find info.. is the fact that you are calling conifers trees.. and though they are.. one might suggest.. that this is where they differ widely ... pruning....

the base line here.. is why .. having a plant.. that is supposed to be one of the most vigorous growing arbs.. to the point where they call it a giant... that you want to make it less giant...

the simply solution would be to cut it to the ground.. and plant one of the other thousand thuja.. that have a much more favorable growth rate....

i just dont see how you crown reduce.. or top.. a plant that claims to grow 3 to 5 feet per year ... giving it a hair cut isnt going to slow it down.. with no insult to the root mass.. it will probably speed it up ....

no comment on the fringe tree...

regardless.. i do not favor 'topping' trees.. and i dont buy the notion that calling it canopy reduction makes it any different..

if something doenst fit in my garden.. it dies.. and is replaced with something with a better annual growth rate.. to insure that it takes much longer to go past it claimed mature height... no tree really stops growing at some magical height...

if you want some real opinions about your plants .. favor us with some pix.. so we can see the situation.. and give you some spot on advice ... rather than theory ...

good luck

ken

Crown reduction differs from what most people refer to as topping by the type of pruning used. Crown reductions employs thinning and reduction/drop-crotching cuts. Topping uses heading/stub cuts. Topping leaves large wounds that are unlikely to be covered over before rot sets in. Crown reduction, when done properly, provides a better chance for the tree to cover its wounds before significant damage occurs. Crown reduction is used as a "last alternative" to reduce wind-load or weight for structural issues, allow for utility-line clearance, or sometimes to improve aesthetics. Topping is performed by those who are not qualified to prune trees in an attempt to accomplish something that they don't know how to do, or, (in some cases) to prune commercial fruit trees when the tree is meant to be around for only a few years and production (including maintenance, harvesting, etc) is paramount to long-term tree health.

For specific advise on applying pruning techniques, one would need to be familiar with the goals for the procedure and the specifics of the particular case (multiple, really good picture might help for that part).

Four, the answer is...it depends. When you remove much of the foliage from the remaining limb, you reduce the vigor of that limb. When you reduce the vigor, you reduce the tree's ability to use that potential new growth to cover over the large pruning wound. As your note suggests, it's usually a good idea to limit reduction cuts to situations where the remaining branch is at least 1/3 of the diameter of the removed portion. If you prune away part of the remaining branch, you have to compensate and change that fraction. So, for instance, you might limit your reduction cuts to situations where the remaining branch is at least 1/2 or 2/3 the diameter of the removed portion.

Lots of things factor in to the decisions regarding crown reduction. The type of tree, the tree's general health and vigor, etc, etc could be considered when determining the likelihood that the tree will be able to recover from the procedure. I have reduced the remaining "new leader", like you show, many times, but I try to evaluate the situation on a per case basis.

Excellent information.
It tells me the general point that I wanted to know
(that it can be ok to reduce a new leader),
and tells me that I do not want to reduce new leaders of
some of the trees on which I am working
(which have few vigor-providing branches).

Yeah, yup, and yes, to Brandon's explano. Perfect. "Drop-crotch", that funny term that gets folks all a-giggling, is exactly the thing one can do with angiosperms, if they really must. And to fast-forward into some truly novel and cutting-edge tree maintenance methodology, there is now a movement afoot to use such techniques to gradually reduce the size of those overmature specimens that are having tip die-back and such....we're talking big, old trees that are in decline...as a sort of means to safely and gently aid said trees in "dying with dignity". Perhaps that's a bit outside of this all, but I found much to like about some workshops that were presented dealing with such. In any case, while a tree surely doesn't "need" to have drop-crotch work done to it, it can occasionally serve man's purposes in certain situations. As for the conifers, mostly not appropriate.

+oM

Way old question (note date) but still the best summary I've read, including "Topping is performed by those who are not qualified to prune trees in an attempt to accomplish something that they don't know how to do, " made me smile

Sometimes having these stale posts pop up works for us....

Marie