Bonsai Technique – Skill level: Beginner/Intermediate

Maples are a must have species in any bonsai collection. A major part of our landscape and culture in Canada, they have beautifully shaped leaves , and can be enjoyed any time of the year with their lush green canopies, fall colours and winter silhouettes. A technique not exclusive to but associated with maples is defoliation. Essentially, the process of skillfully removing leaves at the correct time. A technique that can be taken for granted. Remove some or all leaves to force a smaller more abundant flush of foliage during the growing season. Easy right ? Ok let’s go pluck all of our leaves ! No Matt, stop.

One of the key base teachings Ryan gives us is to always ask ourselves “What do we want to accomplish?” Smaller, more refined branching, smaller leaves and rich fall colours of course! That is an aesthetic goal and while yes, bonsai is in large an aesthetic art form, we have to always remember: horticulture first. These are living creatures. If the tree is weak then we want to build strength, we don’t defoliate. If the tree was just repotted, we want recovery, we don’t fully defoliate or perhaps not at all. If the spring flush of growth hasn’t hardened off, we don’t defoliate. Yes we want smaller and more dense foliage. Yes, the act of removing leaves does indeed help towards ramification of branches and leaf size, but it’s important to understand the nuances in timing, technique and aftercare. Here are some key points, basic or advanced that I have learned:

  • Defoliate maples in late spring to early summer. (Mid-May to late June).
  • Different maples will have nuances about defoliation. Generally partial defoliation is safe. Best to check for each.
  • Other deciduous species like elms for example are pruned at the same seasonal timing leaving a certain amount of leaves or nodes. The goal and process is similar to defoliation.
  • Generally you don’t defoliate trees from which you want fruiting or flowering.
  • Defoliate after the first major spring flush has hardened off. This is the indicator it’s good to go.
  • Cut no more that halfway down the petiole to protect the new buds, leave the petiole to fall off on its own.
  • The petiole will continue to “feed” the tree and protect the new buds until it’s taken all it needs from it.
  • Cut the larger leaves first leaving some of the smaller leaves , if possible keep a few at branch tips.
  • A fine technique to develop is grabbing multiple leaves at one time and severing the petioles with one cut.
  • Move slowly , develop the eye and physical technique. Speed will come in time on its own.
  • To safely defoliate a tree, don’t remove beyond 5-10 percent of the foliage, depending on the vigour of the tree.
  • Use this time to trim back advantageous new branch growth , suckers etc , bringing back the intended structure of the tree.
  • Also check for wires biting in and remove if necessary.
  • After defoliating , be aware the change in water consumption. It will not need as much water but still crucial to maintain the balance.
  • Semi-shade / dappled sun is a good place during recovery from defoliation.
  • When the new buds start to emerge, water needs will increase accordingly
  • Defoliation actually makes the tree “age” twice in a growing season and will promote more intense fall colours as well as smaller leaves and more branching.
  • It is advised by some to stop fertilizing until the new flush starts to grow. This year I have not stopped or changed any regiment. They are fed as all other growing trees are.

To show an example of how much is removed as well as resulting progress here are two trees very precious to me. I got them from my sensei Linda. What’s even cooler is she made both of these incredible pots. I am a big fan of her bonsai pottery.. These two trees are Amur Maple, acer ginalla, they are often scoffed at for bonsai but frankly they are tough as nails compared to Japanese maples in the Quebec climate and the leaves do get quite small if you can stay on top of the advantageous shoots ;).

Close up of remaining petioles and a little foliage after defoliating.
Acer Ginnala – Amur Maple #2 May ‘19 pre-defoliation.
Acer Ginnala – Amur Maple #2 defoliated June ‘19

Here is another one of my Amur maples that was defoliated a couple weeks earlier and is responding nicely. You can see the cut sites from defoliation and pruning now resulting in new more abundant small shoots. This will look really special with their fall colours and these pots.

Acer Ginalla – Amur Maple #3 June ‘19 after defoliation
New growth and cut sites after defoliating. Most of the petioles have already fallen off in the wind.

While the trees may look ugly without their leaves for a couple of weeks, the payoff is tremendous. If timing is done just right , you get tons of smaller new branch options , a fresh, clean healthy flush of smaller leaves and even back budding! With the addition of more intense fall colours , this is a technique that’s worth having on point.

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