Training pines for bonsai is all about creating and maintaining balance. Pines are quite apically dominant, and are quick to shade themselves out, which means they tend to grow tall, with sparse interiors and wide bases. For a sport where we strive to keep growth short, dense, and close to the trunk, plenty of intervention is necessary to keep pine bonsai in check. Primarily, this is done with four seasonal techniques:
1. Spring candle-pinching
2. Summer candle-pruning
3. Fall (through spring) needle-thinning
4. Fall bud selection
Today, we will focus on needle thinning. This part of the balancing act involves letting the tree get full (dense) enough to gain strength, but not so full that the interior buds weaken or die. Therefore, strong trees are thinned earlier…such as during summer candle-pruning all the way through late fall. Weaker trees are thinned late winter to early spring, so they’ll gain strength from the extra time with more foliage.
The process is simple, hold the base of the shoot with one hand, and pull the needle straight out with the other. It’s best to start by removing downward-facing needles first, then the large needles that stick out from the profile. Finally, finish the shoot by standing back, and identifying dense areas that need to be thinned further. Generally speaking, leave more needles on the bottom, less on the top.
Notice the sheaths that remain. Pulling needles one at a time leaves the sheaths in tact, increasing the potential for back budding in those areas.
Let’s start with an example using a weaker pine. This corkbark cultivar, Taihei, was candle-pruned in June ’10, and it did not bud again until ’11, so it was weakened. Although it grew well in ’11, I left all old needles until spring of ’12:
2010 after candle-pruning. It did not grow any more that year:
2011 after the growing season:
2012 March, after needle-thinning:
Notice how the lower area is denser than the upper area. It’s to balance the strength:
1. Denser lower area provides more energy to these branches.
2. Thinner upper area reduces energy to these branches, and allows more sunlight to reach interior areas.
This year, the Taihei back-budded nicely and filled in well. Here is a shot of it today:
Bud thinning, before:
Next, a strong pine, candle-pruned in July, and thinned out in late September.
Needle-thinning another corkbark black pine, Kyokko Yatasbusa, before: