The Buzz

Pinus thunbergii (Japanese Black Pine) Pruning

May is a busy time of the year in the garden.  There is a plethora of planting, including annuals, perennials, trees and shrubs. The education staff is busy teaching students all about our world and the plants inhabiting it. Live at the Garden is ramping up for a busy season, and weddings are constant. All of these activities are vital to the garden and its continued growth, but in my humble opinion (granted that it is VERY subjective), one of the most important tasks to accomplish during this busy month is the pruning of the Japanese Black Pine.

  Pinus thunbergii is a gymnosperm (non-flowering plant) native to the coastal areas of Japan and Korea, tolerant of the constant salt spray that accompanies these sights. The needles on this pine occur in pairs and are dark, lustrous green, ranging from 2 ½” – 4 ½” long, and typically persist on the tree for 3-5 years.  There are a handful of cultivated varieties (cultivars) in the trade, with one of the most popular being “Thunderhead,” but it is this gardener’s opinion that the straight species is the most typical to come across, easiest to grow, and the easiest to work with.

Most of the pine trees located in Seijaku-En, The Japanese Garden of Tranquility at Memphis Botanic Garden, are Black Pine, but we also have specimens of Pinus densiflora (Japanese Red Pine), P. strobus (Eastern White Pine), P. parviflora (Japanese White Pine) and peripheral plantings of native P. elliottii (Slash Pine) and P. taeda (Loblolly Pine.)

Why do we prune Black Pine during this busy time year you ask? The simplest answer is that the candles, new growth, are elongating and we can control the trees growth, and more specifically their direction of growth, by either shortening or removing them. Candles on Black Pines typically come in groups of 3-4, though on more aggressive areas of growth, such as the top of the tree, you can see bundles of 5 or so.

So, why bother to prune the trees? For one, it regulates the size. Black pines, if left to their own accord, can grow to 40-50’ tall with long sections of growth. The pines in our garden range from 2’ -25’ tall, so we want to keep them small with more compact growth. Secondly, we want to style the tree in a Japanese fashion in that they look similar to what you would see along a sea coast; contorted by the constant harassment of the elements. This makes the trees look windswept, dwarf and contorted. Pruning also helps different parts of the tree either grow or not grow. Realizing that this might not make a whole lot of sense, let me explain. The top growth of trees is typically the most robust.  It has the most dominant leaders (growth) and receives the most amount of sun. By thinning (pruning) the trees, we open the canopy up, letting rays of sunlight hit the lower branches and in turn producing more growth. Having this more open canopy also allows more air movement which helps with pest and disease issues. The overall effect of the pruning on the tree is a dwarfing similar to what you see in bonsai.

I have only scratched the surface of this whole process in this blog post. There are many other elements to consider when pruning that are only learned through rigorous study and practical experiences. If you are interested in learning more on the art of pruning Black Pines, please feel free to contact me, as I am always looking for volunteers. (I have a lot of trees to prune!!)

Nick Esthus Curator of Seijaku-En  

Posted by nick esthus at 2:07 PM


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