Posts tagged “Thuaj

It’s Time to Prune Your Eastern White Cedars

Rather than try and tell you how it is, I will instead quote Toronto bonsai veteran Reiner Goebel, who has several decades more experience with Thuja occidentalis than I do.

“As all trees, cedars shed old foliage in fall. Some time in September, part of the foliage, usually in the interior of the tree, will turn rusty brown and slowly fall off. If you’re not sure whether your tree is shedding or dying, pulling at the brown foliage is a reliable test, because the foliage about to be shed comes off easily, while the foliage about to die requires a lot of force to come off. I believe to have noticed that this natural shedding can be reduced by timing one of the heavy pruning sessions to occur around the middle of August.” -from Reiner’s article about Eastern White Cedar at

One of my bonsai teachers also puts it well: “Decide which foliage the cedar will lose, or it will decide for you”.

As Reiner says, it is usually the older interior foliage which is shed – yet this is probably the foliage you want to keep. So pruning generally involves shortening the strong fronds at the tips of branches and those strong ones jutting off the sides. Strong “runner shoots” that often appear sticking straight up at the crotches of branches should also be removed.

This is especially important on collected cedars that are early in their training, since interior foliage is usually sparse and weak (if it exists at all). Late summer cutting helps the tree hang on to that stuff so it has a better chance of gaining interior strength the next year.

This tree serves as an example, a small Thuja collected in Spring 2012. It has been slow to find its legs and is still not at full throttle, but this pruning is necessary to maintain the precious interior growth. Last year it was not pruned at all. Only Thuja that show exceptional growth following spring collection should be summer pruned during their first year of captivity.

Before pruning:


After pruning:

In the first few years post-collection, August pruning may be the only cutting that a Thuja will get, while the rest of the year is spent developing a foliage mass. Healthy cedars, like junipers, grow all year and require several pruning sessions.