Decandling cork bark Japanese black pine
Decandling cork bark Japanese black pine
Decandling cork bark Japanese black pines is very similar to decandling the non-cork bark trees. The main difference is that cork bark pines are usually less vigorous. A general rule of thumb is to decandle them every other year, ideally showing them in the years after which they’ve been decandled.
I decandled this tree for the first time in 2009. It came out very strong so I’ve decandled it a second time this year. We’ll see how it comes out in fall.
Before decandling – front
After decandling
Before – back
After decandling – back
I plucked a handful of needles from the strongest areas, mostly near the top of the tree, to help balance the new growth. The lower branches are weaker – I left all of the old needles in these areas.
Decandled shoots
Decandled shoots
Considering the many factors that contribute to successful decandling, I’m leaving the fertilizer in place throughout the decandling season. Normally I’d remove it all when I decandle. But because cork bark is somewhat weaker than pine, I’m giving the tree the slight advantage of getting fertilizer while it forms summer shoots. I’ll add new fertilizer according the to typical decandling calendar – little by little beginning about 4 weeks after decandling – and end up with a lot of fertilizer on the tree by fall. I’ll leave the fertilizer in place until the very end of the year – the mild winters here make the growing season long.
Why decandle?
There are many techniques for developing Japanese black pine bonsai: pinching, plucking, and pruning among them. All are necessary, but none do the work of decandling. I’m surprised each year at how well decandling balances vigor, improves ramification, and reduces needle size.
I began caring for a cork bark Japanese black pine in 2004. After several years of restoring the tree’s vigor, it was time to decandle. Just a year and a half later, the tree more than doubled its ramification.
Before decandling – January 2009
18 months later – June 2010
The tree still needs plenty of work, but that’s part of the fun. As long as there is progress, the work is bearable.
You can see the tree with moss at Bay Island Bonsai’s gallery of the 2010 Exhibit.
Decandling secrets revealed!
Remove the new growth from your pine bonsai and you’ve decandled the tree. Within a month or two, new shoots like these will appear:
Summer growth – Japanese black pine
Easy enough. Place another pine on the turntable, pick up the scissors, and get started. How to make that first cut? I typically consider the following:
Tree health
- How healthy is the tree? If the tree is not strong, I’ll try again next year.
- How much fertilizer did the tree receive in spring? I’ll only decandle if the tree has been fed heavily.
- Was the tree decandled last year? If so, did it come out strong? If not, I’ll wait.
Timing
- Large tree? Start decandling sooner.
- Small tree? Decandle later.
- Decandle in one day or over time? I usually decandle show trees and dramatically unbalanced trees over time.
Relative shoot strength affects my decision of when to cut, whether or not I leave a stub, and how many needles I pull. Along these lines, I ask:
- Am I working with big candles (stronger) or small candles (weaker)?
- Exterior growth (stronger) or interior growth (weaker)?
- Apical growth (stronger) or primary branch growth (weaker)?
- Are there many old needles (stronger) or few old needles (weaker)?
- Removing fertilizer slows new growth – leaving fertilizer in place after decandling gives summer shoots a boost.
- Over watering yields longer needles – less water yields shorter needles.
Even if I get everything right, the tree will still be subject to a final, and very important variable that is quite out of my control:
- Warmer summers produce stronger summer shoots.
- Cooler summers produce weaker summer growth.
Together, this great mix of variables contributes to the final result. Sometimes it’s pleasing, other times it’s disappointing. But as long as the tree remains alive, I’ll have another chance to get it right next year.
Decandling techniques
The practice of decandling refers to the removal of spring growth on pine bonsai. The goal of the practice is to balance growth and reduce needle size. Simply removing spring growth from a pine will result in smaller needles, but it will only go so far towards balancing the tree’s growth. Over time, the bonsai community has developed a number of techniques for this. The method I learned first is sometimes referred to as the “10-day technique” or even the “10-day, 10-day, 10-day” technique. It’s easy to learn and it works well. The steps:
- Divide the tree’s growth into 4 zones depending on vigor. Zone 1 is the weakest, zone 4 the strongest. (See “Decandling basics” for details)
- Remove the new growth in zone 2.
- 10 days later, remove the shoots in zone 3.
- Another 10 days later, remove the shoots in zone 4.
The process takes 20 days to complete. How does it work? The longer a shoot has to develop, the more time it has to gain vigor. By removing weaker shoots before removing the more vigorous shoots, we give the weaker shoots more time to “catch up” and grow strong. Stronger shoots get less time to develop – this keeps them in check. The very weakest shoots are left alone. Decandling very weak branches can significantly slow them down or bring them to a stop. Letting them grow for a year increases their strength.
Do I need to divide a tree into 4 zones? What if I wait more – or less – than the required “10-days” between removing each set of new growth? Adjustments to the basic technique are always available. What if I don’t have time to work on my tree three times over the next three weeks? There is a technique for that too.
The next method I learned is sometimes called the “stub technique.” It’s a great way to decandle a tree in a single day. The steps:
- Divide the tree’s growth into 4 zones depending on vigor. Zone 1 is the weakest, zone 4 the strongest.
- Remove the new shoots from zone 2.
- Remove the shoots from zone 3 – leave a small stub at the base of these shoots.
- Remove the shoots from zone 4 – leave a large stub at the base of these shoots.
“Small” stubs are about as long as the diameter of the shoot. “Large” stubs are about twice as long.
Spring growth
Spring growth removed
Large stub
Small stub
No stub
No stub – detail
Where, precisely, to make the cut for the weak “no stub” branches? Just above the line between last year’s growth and the spring shoot. Because adventitious buds develop from tissue in the new growth, cutting into last year’s growth prevents adventitious buds from forming and encourages needle buds instead. This subtle difference defines a line between decandling and pruning.
What makes the stub technique work? I’m not sure. Somehow leaving a stub slows summer growth making it a great technique for balancing a tree’s growth.
There are a number of refinements on this technique. Instead of leaving stubs, I sometimes remove needles from the more vigorous shoots. Sometimes I leave stubs and remove needles – it depends on the relative vigor of the branch I’m working on. I’ll say more about that later this week.
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