AusBonsai

Can this be done any time throughout the year other than fall/winter without detrimental effect of the health of the tree? I ask this because last years needles are way too long and they continue to lengthen causing shading on new buds and needles.

Needle shortening on pines is a gradual process, involving pruning, needle plucking, candling and several other things. That makes too long and complicated a chapter to figure in a thread like this. Here is the explanation you need:
http://www.bonsai4me.com/SpeciesGuide/Pinus.html
You will see that it also includes info on the J. white pine, which, if I remember rightly, you were also interested in.
I would also like to add that my friends in the Tropics all battle with needle length, even more than we in cooler regions do. You have the plus of fast growth and the minus of large foliage sizes...
Apart from reading the online info, go and see the Lindsay Bebb bonsai nursery; see http://www.bonsainursery.com.au/public/about.ehtml What they don't know about growing pines in the Tropics isn't worth knowing.
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It suddenly occurred to me that what you want to know is whether you can shorten the needles by cutting part of them off. The answer is Yes, sure, and you can do it now. Remove 1/3 to 1/2 of the long needles. The ends will turn brown, that's unavoidable. Sometimes you get a lot of backbudding with adventitious shoots in awkward spots that cast a lot of shade. Those can be removed. But some new shoots might be just where you will need them in future. Once again: get some help from experienced bonsai growers, it'd save you a lot of time, frustration and money!

Lisa

vlkcheng wrote:Can this be done any time throughout the year other than fall/winter without detrimental effect of the health of the tree? I ask this because last years needles are way too long and they continue to lengthen causing shading on new buds and needles.

Hi VLK,

I think you need to be more specific. Do you mean trimming needles shorter to open up light, or do you mean growing of shorter needles? I'm not going to pretend to know enough to answer either, but they are very different questions.

Cheers,

Andrew

Hi Andrew,

My post was being written while you posted your reply. Sorry, I didn't mean to steal your thunder!

Lisa

sorry for the confusion. I mean can you cut the needles shorter at any time during the year?

See my reply above.

Lisa

great, thanks for all your help.

Does trimming the needles slow growth down at all?

LLK wrote:Hi Andrew,

My post was being written while you posted your reply. Sorry, I didn't mean to steal your thunder!

Lisa

LOL.

Andrew F wrote:Does trimming the needles slow growth down at all?

Andrew, I'm no expert on pines, but in all trees needles/leaves are the food factory right, so it figures that if you chop 'em off, then the tree will make less food and have less energy, resulting in less growth. That's the way I'd see it. I guess it could also be used as a form of energy balancing, so probably to leave any weak areas of the tree with full length needles and cut back on other parts, but again, that's just an opinion based on my own form of common sense . . .

Cheers,

Andrew

Can't see anything wrong with your reasoning, Andrew L.
Worth a mention: some people use the cutting of needles as a substitute for needle plucking.

Lisa

I agree that you can cut needles off of your JBP at anytime of the year, but what are you trying to achieve?

Unless it is really dense I am unsure that it'd be useful.

Post a pic of the tree.

*Note that cutting needles short are not a substitute for proper technique.

Scott, vlk is in the Tropics and he writes this:

I ask this because last years needles are way too long and they continue to lengthen causing shading on new buds and needles.

Right now, I think that cutting the needles is the best thing he can do.

*Note that cutting needles short are not a substitute for proper technique.

I fully agree. The only situation I can think of, in which it is useful, is when you have a delicate tree or branch and wish to leave the fascicles of needles in strategic places, so that you get new buds there, without handling the tree too much. In that case you cut back the needles to the tops of the fascicles. If you want to make sure that you don't get shoots where they are not wanted, you pluck the needles or cut them off at their base.

Lisa

Hi Lisa, are you saying if you pluck needles then you won't get any shoots in this area? I thought if you plucked at the right time and technique the sheath would remain an buds may come from this spot providing the tree is healthy and well fed.... I'm no expert on jbp but thought I had read this somewhere??

Hard to tell what to do to the tree without a pic.

The problem with leaving needles in strategic places and using needle buds is that you get large portions of branches that will never form buds (bare necks). The much more preferable back buds are the ones at the base of the extension (adventitious buds). If you continue to use needle buds, the tree gets leggy.

Matlea,
If you pull needles chances are you'll remove the dormant bud (between the needles) too. This is not a major issue because as mentioned above, it is better to use the adventitious buds that you cannot see at the base of the candle.

Back budding on older wood with no needles will occur at the base of extensions. If you want to use needles buds when the needles are gone, most of the time so is the bud and any chance of back budding.