Daisugi or Coppicing

Cathy Kavassalis – Halton Master Gardener

I have a relatively new neighbour down the street. He cut back a large number of small white pines and at first I thought he was some novice gardener and was well, mutilating them, to be honest. But my cultural bias failed to let me see the merit to his technique. Now I watch with fascination, as those trees develop interesting forms and are providing a unique hedging for his property. I mention this as a segue to what I really want to share.

Circulating on reddit right now are images of an ancient Japanese practice called Daisugi. My son asked me if I knew about the technique. I did not, and had to research it a bit. It expanded my understanding of forestry techniques and of cultural practices and thought it was worth sharing and discussing with you.

Daisugi is similar to other coppicing or pollarding practices that were used to create a continuous harvest of timber from a single tree. However, there are some unique differences.

Long ago, particular species of trees were found to produce perfectly vertical uniform trunks. It was discovered that pruning techniques could be used to create large lateral branches that could support many vertical trunks. These could be harvested over time and the parent tree would continue to produce harvestable lumber for centuries.

Several species of trees were used to create Daisugi forests, in particular Cryptomeria, Japanese cypress, like the Hinoki cypress, C. obtusa, with which some of you may be familiar. Only certain varieties of species produced perfect trunks and certain cultivars were selected to create forests. This reduced genetic diversity meant the forests became vulnerable to disease and pests. Both from a forest health perspective and a labour cost, the practice has largely been abandoned. But some ancient trees remain, testaments to the effectiveness of this practice. While sustainable for many centuries, the evolution of pests and disease never ceases and practices must co-evolve. Back to my neighbour …

We have much to learn, from our past, from our neighbours, from cultures around the world. It is through sharing communities like this that we can broaden our understanding of the world, of gardening and many ways for caring for the flora of our planet. I want to thank each and every one of you for contributing to our learning and growing community

Here’s a video about the Kitayama Cedars:

https://www3.nhk.or.jp/nhkworld/en/ondemand/video/6024009/?fbclid=IwAR1OV31KxlTvx366T-qQglfuRhzEXpKav5sSpZ28bR7nkfJYcpM3Gsr_YRo

HOW NOT TO PRUNE A TREE

Several years ago, another neighbour (who has since moved away) decided they wanted to reduce the size of their linden (Tilia cordata) and hired a poorly trained arborist to prune it. I happened to be passing by while they were cutting off the branches and asked them what they were doing. They responded that they planned to top the tree. That practice is against our tree protection bylaw here in Oakville, and I explained that to them. When I pulled out my cell phone to snap a photo, they abandoned the job rather abruptly. What happened? Now five years later the area that they pruned is dead. (See photo below – current)

Pruning incorrectly can kill a tree. Topping, in particular, is a very harmful practice in which branches are sheared off at a uniform height. This shocks the tree and reduces its ability to support its root system. Many tree species will respond by creating water spouts.

The tree cannot seal over the large wounds. Wood borers and disease can invade, causing decay and rot in the tree. It generally dramatically shortens the life of a tree and can be really disfiguring.

Some trees, like London Plane (Platanus x acerifolia), are amenable to severe pruning techniques like pollarding or coppicing. Pollarding is different from topping. It can be done only to certain deciduous trees that sprout readily after pruning. Examples include: certain species of beech (Fagus), oak, (Quercus), maple (Acer), black locust (Robinia pseudoacacia), hornbeams (Carpinus), lindens and limes (Tilia), planes (Platanus), mulberries (Morus), willows (Salix), etc. This specialized method must be started while a tree is of a young age. Over time, it can produce a somewhat Tim Burtonesque framework, (see image of Berkley plane trees above). It requires annual upkeep.

Pruning must be done carefully, with knowledge of the tree species, growth patterns and an understanding of potential risks.

Why should you prune:

to promote plant health of the tree
to maintain a plant for an intended purpose (flowering, fruiting, hedging, form, …)
to protect people and property

Basics Before Pruning

Prune small and limit the total amount of branches removed at any time.
Prune well by:
- making correct cuts
- with clean tools
- timed to avoid insects and diseases
- disposing of pruned material appropriately.
Respect the natural form!