Posts tagged “pruning

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 RGBonsai.com

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.


Pruning Ginkgo to Develop Ramification

Ginkgo have a bad reputation for developing ramification, but that doesn’t mean they don’t ramify at all – they just need some encouragement! Unlike other deciduous species like Maple or Elm that will develop some ramification even with improper cutting techniques, Ginkgo will barely ramify at if they are not cut properly. Still, even in the best of cases, Ginkgo ramification cannot hold a candle to that of maples… but that is just the character of the tree. They are still a great species to work on.

This post outlines the pruning techniques I use on my Ginkgo in USDA zone 6.

The first step is making sure the tree is growing strong. This tree was repotted in March but has grown better than expected.

I don’t cut my ginkgo until it is showing very strong shoots like this (about five pairs of leaves). This gives the tree some time to build up strength. I find that if I cut it too early, the tree doesn’t respond well.

Here is a typical gingko branch. The buds circled in red are backbuds. Ginkgo backbuds very well, and most buds open up in the spring. However, the problem with Ginkgo is that it is hard to get these backbuds to extend into twigs. Usually only the end of the branch (circled in blue) will extend during the growing season and the backbuds will just form winter buds. Therefore, you need to cut back the tip of the branch to one pair of leaves to redirect some strength to the backbuds. This is a rather weak branch, so the side buds may not even start to extend until the process is repeated next year. Again, I find that if the tree is allowed to gain some strength in the spring, you will have much better luck getting the backbuds to extend.

Here is a stronger branch after cutting the tips back. This branch is strong enough that I would expect some of the back buds to extend.

Strong apical nodes that have not yet extended may have 3-5 leaves instead of the usual 2. Cut off some leaves to leave just a pair. This weakens the outside of the tree and allows more light into the inside. This is especially important for the top of the tree since Ginkgo are very apically dominant.

After cutting. I will continue to fertilize the tree heavily and the process may be repeated again in the summer. Further leaf-thinning may occur throughout the season.

Really, the pruning techniques for Ginkgo are very similar for most deciduous trees. The development is just much slower and the end result less ramified. However, I’ve found that by using the above strategy, I can increase the twigginess of the tree by about 50-75% each season.