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 basics – Japanese black pine
Decandling basics – Japanese black pine
The basics of decandling Japanese black pine are straightforward. The application of the basics is more of a long-term pursuit.
At its most rudimentary, decandling is the practice of replacing vigorous spring growth with moderately-vigorous summer growth – a technique for removing one shoot and replacing it with two. It’s a powerful tool for balancing black pine growth.
The technique has been practiced for roughly half a century. Saichi Suzuki, father of the famous Daiju En bonsai garden in Okazaki, Japan, stumbled upon the technique after awaking to find the new shoots of a Japanese black pine munched away by some critter. Over the course of the summer, new shoots replaced the spring growth. Curiously, the summer growth was more refined than the spring growth – the shoots were shorter, and more importantly, the new needles were shorter. Black pine had long been a challenge for its long needles. What Suzuki realized, upon witnessing a black pine bonsai produce shorter needles, was that there might be a way to produce the effect with predictable results.
Many years of experimentation led to today’s decandling techniques. Daiju En has since become known as the world’s premier bonsai garden for black pine.
Below is a photo of a black pine in January. Most of the needles are short from the previous year’s decandling, though you’ll notice a few longer ones if you look closely. These are from weaker shoots that weren’t decandled last year to help them recover their vigor.
Japanese black pine – January, 2009
Several months later, pines lose their tidy appearance. Spring shoots appear all over, usually more vigorous toward the apex. Several years of this unbalanced growth can quickly produce an ungainly effect. Here’s the same tree pictured in June.
Black pine with spring shoots – June, 2009
This is the time to decandle – when the spring shoots have matured. The precise date depends on many factors – I’ll cover these in another post. I’ll also outline some of the many approaches to decandling.
Note that decandling only works well for healthy, vigorous trees. Weak trees, or trees that didn’t receive a lot of fertilizer in spring aren’t good candidates for decandling. Because the technique significantly decreases a tree’s vigor, I always think carefully before clipping away.
Step one is dividing the tree’s growth into several zones. A popular approach entails identifying four. Here they are from least vigorous to most vigorous.
Spring growth
The weakest shoots are left alone – the more vigorous shoots are removed.
It’s important to be precise in the cutting of the new shoots. Little details like the angle and location of the cut can have a big effect on the result. Here is a prime candidate for decandling.
Japanese black pine – two years’ growth
The cut must be made perpendicular to the shoot – sharp scissors are a must.
Keeping scissors perpendicular to the shoot.
Spring growth removed
Optional technique – thinning last year’s needles after decandling
That’s it – the basics anyway. Decandled pines look bare at first, but fill in well between June and October.
Decandled pine
How well a pine fills in depends on a number of factors, some in our control – water, fertilizer – and others far from our control – like the weather. Fertilizer is typically removed at decandling time and slowly re-introduced over the course of the summer. Watering, as always, must be monitored closely. Although decandled pines drink less than trees with rapidly growing shoots, decandled trees do appreciate humidity and are good candidates for frequent mistings in dry areas.
One of the best ways to get started with decandling is to find someone local who has demonstrated success with the practice. Look carefully – they can be hard to find!
Decandling black pine – case study
Decandling black pine – case study
It’s common to divide a tree’s shoots into three zones based on strength during decandling season. A long-term project of mine had me dividing a tree into three zones for very different reasons.
Japanese black pine – after decandling
The lowest third of this sixteen year-old Japanese black pine is beginning to develop branches that will be used in the final design of the tree – these I decandled. The top third of the tree – two vigorous sacrifice branches – are not decandled. These branches are facilitating future grafts by providing scions and keeping sap flowing past the spots where I need to graft.
The branches growing from the middle of the trunk will comprise the apical branches. I’m keeping the spring shoots here to facilitate approach grafts next season. I’ve never tried approach grafts with black pine and am curious to give it a try.
After decandling
After decandling – first branch on the left
Decandled branch
Spring shoots retained for approach grafting next year
What I’m most looking forward to is removing the top half of the trunk. I’ll do this a year or two after I can get grafts to take near the top of the tree. Then, another five years of decandling or so and the tree may be ready for exhibit at a young 20-25 years old.
Decandling a red pine forest
Sixteen years ago I planted a group of red pine seeds. I made seedling cuttings, watered, and fertilized the trees, but never created a plan for their future. As a result, fate determined their present form. The trees were healthy but ungainly – perfect candidates for a forest planting.
Red pines are a very vigorous variety. Cutting them back hard seems only to trigger more vigorous growth. Timing, in these cases, becomes an important ally for managing new growth. By May, new shoots had covered the trees, but it was still too early for decandling.
Strong growth in May, but too early to decandle
By the mid-June, the trees had filled in considerably. This was a good time to decandle.
Red pine forest before decandling – front
Before decandling – back
It was hard, at first, to get past the new growth and find where to cut. Once I had cleared an opening, the work went quickly.
Getting started
I left stubs at the base of the most vigorous shoots. For less vigorous shoots, I removed shoot and stub. I left the weakest areas of the tree alone so they can regain vigor and help balance the foliage.
Vigorous new shoot
Vigorous shoot removed – note stub
Leaving stubs is a technique for slowing the most vigorous shoots. I can’t explain why it works, but experience has proved it to be a good technique for balancing growth.
I also removed a lot of old needles as I worked. I removed more from strong areas, fewer in weak areas. As with the decandling, the goal is to balance growth.
Decandled branch
One tree down, five to go
After much clipping and plucking, the trees looked pretty bare. I’ve removed a similar amount of foliage from these trees before and expect them to fill in again by late fall. Careful watering and fertilizing will help – a warm summer will help more.
After decandling – front
After decandling – back
Strong area – candles and old needles removed
Weak area – spring growth retained
Mixed area – strong growth removed and weak growth retained
Although I’m confident that the tree will come out well this fall, I know not to expect too much. Decandling is a funny practice. Sometimes the trees come out a bit too strong, other years, too weak. I’ll provide updates along the way and we’ll see what this year brings.
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