Dan, the very best window of time for the pruning you discuss is from right now up until just before bud swell. As to your second question, yes, there may be a bit more energy flow to remaining growing points, including the leader, which typically has an advantage anyway. I do not believe though that limbing up trees causes any increase in trunk girth. In fact, the opposite is more likely.

+oM

Limbing up trees doesn't make the trees girth get larger. Also now is the best time prune. I was pruning sugar maples in my yard and the sap ran out. But to doesn't hurt the tree.

i do it when i walk by with the saw.. avoiding spring growth time.. because all that sap makes sawing hard ... i dont care about weeping.. dripping.. and bugs ... it would be a different story if my retirement were invested in 10,000 acres of production/profit trees ...

think of it this way for simplicity .... an 'established' tree has a finite root system at any given time ... and that root system can support the canopy above ...

if you remove some of the canopy ... on an established babe ... its has that much more root energy for what is left.. so usually.. it 'seems' like the tree explodes in growth in the next year or two ... and i say 'seems' .. because once they get going.. you can really see the growth.. as compared to the result of pruning on a very large tree ...

and you dont mention the age of your trees.. but no severe canopy reduction for at least two years after planting .... they need the leaves to grow the roots.. etc ...

as to forcing the trunk to 'beef up' .. only time .. age does that ... there is nothing you can do .... to speed it up ...

i presume you will find out about the shade tolerant conifers .. in the conifer forum ...

make any sense???

ken

Yes, prune BEFORE spring for oaks to prevent disease spread. Maples I would wait until after leaf out (as mentioned above - the freeze/thaw that is coming causes all kinds of messy sap bleed. I did that to a sugar maple, and while supposedly it doesn't hurt the tree, it is hard to watch). Not sure about beech as we don't have any around here.

What is the percentage? Remove no more than 1/4 of the tree's photosynthesis capacity in any year?

Not that I expect you have any ones in a wild area but casual observation leads me to believe limbed up Dawn Redwoods actually have a more narrow trunk.

To get a thicker trunk earlier expose the trees to more wind. The combination of top twig damage and having to hold themselves up seems to encourage trunk growth. Once again not a scientific observation.

toronado, 25% (or less!) is what I have heard also, especially if the tree was heavily pruned before in recent years. Better 12-1/2% over a two year period! Leaving lower branches definitely aids in developing good trunk taper. Many folks planting new trees make two of the worst mistakes by "limbing them up" right away and staking them, both of which reduce development of trunk taper.
hortster

A quick suggestion. If your trees are relatively young and you're worried about removing too much of the photosynthetic capacity of the tree, you can just removed a portion of the lower limbs. Cut them about in half this year and then remove them completely next year. This will allow for some additional leaves for energy creation on the partially pruned limbs, but you'll still get some of the benefit of diverting energy up the tree.

Corkball has it right for the suggested pruning times by species.

Oaks before April because of oak wilt spread by insects.

Maples, Birch and Beech can be pruned now but the sap can be extremely annoying and messy. Its not like it washes off during the next percipitation. I like to prune these after they leaf out. I'll typically avoid it during July and August.

At the end of the day I've pruned trees at all times of the year. The only rule I really stick to is the Oak rule.

Pruning from now until bud break allows for the shortest possible time for the plant to be unable to close the wounds. Also, energy flow is poised to make quick work of this.

We prune several thousand trees a year, and yes, we do it at all times of the year except bud break and leaf fall. All other times are acceptable, with the exception of pruning oaks and elms during insect vector season.

+oM

Ok, english is not my main language...What does "leaf out" mean?

Dan

The leaf sprouts from a bud. After the leaf fully expands.

In this pic you can see buds breaking and leaving out (glad I have a reason to post this pic, it was so pretty in person)

{{gwi:330298}}
By jp_42_82 at 2012-02-08

Jon, did you ever end up getting one? Fall color was pretty sweet on mine.

{{gwi:330300}}

Watcha got there, whaas? Methinks some variety of J-maple. Nice bark coloration.

+oM

Its called an experiment!lol! I might be in good shape though as it was large to begin with and this mild winter won't impact its ability to establish. I know I'll get dieback at some point. But that will only promote new bright red twig growth anyhow.

Its A. p 'Sango Kaku'.

Well, it looked good at picture time!

=oM