Updated: Jan 7
Much like the discussion we had about pinching junipers concerning the fact if we should pinch or not the same discussion can be had for Japanese Black Pines and needle cutting, So lets jump in and take a deeper look.
I've been asked about this a few times and seen posts on Facebook pages about it or have seen people post photos of pines with cut needles and people usually weigh in on the subject. Today i will throw my opinions on the matter into the hat so you can have as much information as possible moving forward.
So the question, should i cut my Japanese black pines needles?
The answer? Yes and No. You didn't think it was that simple did you?
There are only 2 reasons i would ever cut black pine needles and they are
a few days before a show to clean up any longer needles poking up out of a pad
to weaken a strong area of a tree to allow weaker regions to catch up ( yes you can needle pluck but having longer needles in the stronger area and smaller needles in the weak area at the same quantity will still result in the stronger area getting stronger as the longer needles produce more energy ).
Now we also need to understand the stage our tree is in and our goals for that tree. If you were growing saplings or young stock to thicken then cutting needles would defeat the purpose of your goal as all you are doing is removing some of the trees ability to create energy it can harness to grow fast. In development if the top of the tree gets really strong and grows big thick branches and swells at junctions we are not bothered by this because we understand we will cut this off when we begin the design phase just before we go into refinement. Now we can still needle pluck to ensure the lower portion of the tree doesn't get to weak and die but needles cutting wont be necessary in this stage and will only weaken your sacrifice branching further then it already has to be. I always tell people in development to keep as much growth on the tree as possible, only remove growth or branches if it starts to cause a problem like the top of a tree getting to strong and killing the bottom off or in the case of black pines whirl growth if you start to get excessive swelling around a junction you need to remove branches at that area to stop the swelling getting any worse. But I'm sure you can understand now that for a young tree in development needle cutting is a pointless act as your goal is to drive as much energy to the tree as possible and halving your solar panels will only slow that process down.
So when would i cut needles then? this is more of a refinement technique or a technique you can use just before refinement, when we now need to take into consideration the balance of the trees energy to keep our bottom branches healthy and to stop our top branches from becoming thicker then our lower branches throwing out our branch structure taper. As mentioned above if a tree does need to be balanced which should really only be in the first year or 2 of refinement, then you can do so by plucking the needles back to the amount that matches the weakest significant branch on the tree which is usually one of the lower branches. What this does is ensure all branches on the tree have the same capacity to create energy so the tree will allocate resources evenly rather then favouring the strongest portion which is usually in nature how they get their growth above the canopy of the forest to get the sunlight. An easy way i usually explain needle plucking is like this, imagine you have 10 houses on a street and the goal is to have all those houses create the same amount of energy from solar, to achieve this you would make sure they all have the same amount of panels ( lets say 10 panels ), now this would work pretty good, but lets say 1 house has 10 panels but those 10 panels are twice the size of every other houses panels and have twice the surface area, That house would be doubling the energy it is creating. It is the same for black pines, we can control the amount of energy a branch has by controlling the solar panels. so lets say we pluck all the branches to an even amount of needles of all the branches but the top branches have longer needles, it makes sense to trim those longer needles to the same size as the weaker needles so now you have both the same amount and same surface area for all needles.
Using this same methodology you can also strengthen an area of the tree, lets just say your first branch isn't the thickest on the tree but you would like it to be, you can get the rest of the tree in check like mentioned above but allow that 1 branch to get out of control and crazy which will cause the tree to favour it and send resources its way as it will be creating the most energy, once you have achieved the thickness you are after you can bring it back into line with the other branches.
i would avoid doing needle cutting in the autumn period going into winter as you will create a lot of open wounds on the tree right before our most susceptible time of year for disease, having open wounds and never ending moisture don't mix, so try save this for late spring early summer. The tree isn't photosynthesising much if at all through winter any way so needle cutting just before that time to slow the trees energy production is really pointless and just increases your chances of problems.
I hope this has helped understand needle cutting a little bit more and gives you something to think about when working on your black pines moving forward, This may or may not also apply to red pines but ill be totally honest i have never owned one and have not seen the results so i cant speak to it, but given they are very similar i would expect to see similar results.
Until Next Time, Enjoy Your Bonsai Journey.