This morning my Senior and Saturday Crew came to cover the five poly houses. Yes, it’s a bit early, however, I hate to work in the cold and the ends of the houses are not covered until late November or early December. I leave for China on Monday for twelve days and since I will also be gone nearly the entire month of October teaching throughout Australia then leading a tour to Japan returning home a couple of days before Thanksgiving, preparations must be made early.

The poly house side is inflated for insulation

This house is not inflated as much

The best bonsai specimens are not in the houses now, they are outside in a full sun exposure and will remain in mid to late November. It’s good if the bonsai experience considerable cold, perhaps 25F, plus a nice dusting of snow. As the snow melts over the trees, it tends to “clean” the bark since the snow is actually a bit gritty. Putting the bonsai in the poly houses too early is not good.  Much of the nursery stock is already in some of the poly houses, but the ends are still open and will be fine.

The fan on the left blows air through the tubing between the two layers of poly for insulation

Rain was imminent this morning, however with the help of Diane and Chris the crews were able to cover the two large houses which have a double layer of white overwintering poly. Two layers are used and a small fan is used to “blow” up the space between the layers of poly which adds insulation. This also keeps the poly tight so it will not flap in the wind.

Working quickly they were able to cover both large houses before the rainy downpour which lasted most of the day. I don’t need to water today! The Senior Crew can easily handle the three smaller houses (45 x 16’) next week while I’m in China if the weather cooperates. They only get a single layer of poly and are easier to cover.

While they were covering the poly houses I was teaching my Introductory Bonsai Course in the studio and was unable to help. But each one of these friends has covered the poly houses before, some for 20 years. They finished just before noontime, as my Introductory Bonsai Course was finishing so we had the traditional pizza lunch together before the afternoon workshop.

During the afternoon Open Workshop we were talking about preparing the trees for overwintering and I remembered seeing a technique in Japan I wanted to share with them. The laptop was handy from my morning class, but has over 36,000 images and could not quickly find the photos I was looking for but found them this evening when it was quieter.

Root pressure from a potbound bonsai has broken the container of this large size bonsai. It has been wired to contain the root ball until a new container can be found or until the correct season– I often use duck tape….

Bonsai with thick fleshy roots, like this Magnolia, are especially vigorous and can easily break containers when potbound.

In November a few years ago, after most of the bonsai tours left Omiya Bonsai Village, I saw Hiroshi Takeyama, Fuyo-en Bonsai Garden, transplanting some bonsai. Since it’s not the common season for transplanting I asked him why he was repotting. He mentioned that it was not a “complete” transplanting, only the outer layer of soil was being removed and replaced with fresh soil to avoid breaking containers during the winter when the soil freezes and expands. Broken pots because of root bound trees is quite common. I have had a few experiences, especially with containers with inner rims. Mr. Takeyama was only relieving the root pressure around the perimeter of the containers because root pressure can be quite powerful, especially for species with fleshy roots like Magnolias. In spring these bonsai will be transplanted.

Hiroshi Takeyama instructing an apprentice on the technique of “temporary repotting.” Notice that the moss has been carefully removed and saved. A repotting tool (sycle or knife) in the left hand will be used to remove a ring of soil around the perimeter of the container.

Fresh soil is being added to the container.

This Japanese maple bonsai has been prepared for the winter by removing soil around the perimeter of the container and replaced with fresh soil. This is NOT how a correctly transplanted bonsai would look. The original central root ball would be irregular in shape with triangular sections of roots and soil removed.

Another potbound bonsai prepared for winter so the root pressure does not break the fine-quality container.

This might be a good technique to use for potbound bonsai to avoid broken containers in spring.