Harry HarringtonArtist and Author, Bonsai4me · Author, Publisher, Webmaster, Bonsai Artist

Partial Defoliation Of Deciduous Bonsai In Summer

8 Jun 2020 · 4 min

Watch on YouTube

3:42

In this instructional video, Harry Harrington demonstrates how to perform partial defoliation on deciduous bonsai during the summer. He begins by pruning the current season's growth on a European beech (Fagus sylvatica) that he started in 2001, explaining how to trace back shoots to the lignified wood of the previous year and cut back to leave one or two new internodal leaves. He contrasts complete defoliation—removing every leaf, which can lead to branch die‑back or fewer, larger leaves—with partial defoliation, where the terminal leaf is retained as a sap drawer to keep the branch alive and suppress embryonic buds while encouraging new shoots from the removed leaf bases. He notes that the visual result of partial defoliation may look unsightly for a few weeks but improves rapidly. He then applies the method to a turkey oak (Quercus serratus), advising against complete defoliation on oaks and suggesting that large leaves be halved with scissors to balance vigor. A hornbeam example, partially defoliated by his assistant Paul, illustrates collaborative work. Harrington emphasizes completing defoliation shortly after midsummer (early July in the UK) to ensure vigorous regrowth, warning that later timing reduces effectiveness. The video concludes with encouragement for viewers to try partial defoliation themselves.

Chapters

The first tree I will show you today is this Fagus sylvatica, or European beech bonsai. A tree that I started in 2001, so nearly 20 years ago. First of all, I prune back this season's growth. As I ensure that my trees are fully pruned before the start of growth in spring, this is simply a case of tracing back the new shoots until I find the lignified or hardened wood of last year's growth. I then cut the shoots back, leaving one or two new internodal leaves. Complete defoliation is where every leaf in the tree is removed. However, the results can sometimes be disappointing, with some branches dying back and some species even returning with fewer, larger leaves. Partial defoliation involves leaving the terminal leaf in place and removing the rest of the leaves behind it. The leaf that is left in position at the The terminus acts as a sap drawer and ensures that the branch will not die back. It also stops the embryonic buds at its base from emerging, while the buds at the base of the leaves that are removed will extend, replacing a lost leaf with a new shoot of many leaves. The appearance of a deciduous tree after partial defoliation is not always satisfactory. However, within a few weeks, the appearance will be be greatly improved, and it's worth just putting up with that appearance for 2 or 3 weeks. The second example is a Quercus serratus, or turkey oak. Typically, oaks have a large leaf in spring, but partial defoliation is a reliable way to reduce their size. Avoid complete defoliation on oaks as this will often result in poor results and on occasion much larger leaves. Where a vigorous branch has produced oversized leaves, the terminal leaf at the tip can be reduced by half to balance the overall strength with weaker branches. Just simply cut very large leaves in half with a pair of scissors. This final example is on a hornbeam that has been partially defoliated by Paul. Paul has spent the past 3 years working in the garden alongside me and works many hours at this time of the year helping me defoliate a large number of cedar trees that I have in my collection. I hope you found this video useful and now have the confidence to carry out partial defoliation on your own trees. Make sure you complete the work by a little after midsummer, which is early July in the UK. After this time, the results may not be as vigorous as should be expected.