Bonsai Studies in Japan: Part 4
by David Johnson
Watering
My bonsai studies included the day-to-day work required to maintain bonsai. Mr. Nakamura sometimes asked me to water his trees. Yokohama in March can get close to just above freezing temperatures at night followed by sunny warm (10° C) days. Some afternoons were quite windy. I usually watered the trees between 10 and 11 o'clock in the morning, giving them a good soaking with the hose while making sure that I got in behind the trees which Mr. Nakamura pointed out to be important. Sometimes in the afternoon after the winds picked up and the conifers were coming out of dormancy, some trees were watered again. Most of the deciduous trees had just started to leaf out. I don't think that my watering technique was ideal since I throughly watered everything. It was probably adequate enough that Mr. Nakamura's follow up care could not correct.
In one instance, I noticed a pinus thunbergii that had yellowish needles. Mr. Nakamura said the yellowing was caused by too much watering. The surface of the pot had been covered with moss so that the soil could not dry out as quickly nor could it be checked for dampness. As a remedy, Mr. Nakamura had already removed a section of moss so that the soil could be checked and the tree's colour could improve with less watering.
Mr. Nakamura liked moss on the soil surface because it looked pretty but it was important to leave an open area to check soil dryness. When trees were repotted, any moss was carefully removed and sometimes replaced before watering. Any moss not used was placed on sheets of newspaper and put into flat trays for use later. Mr. Nakamura said that if the moss dried out it could be ground into a powder and sprinkled on the soil and regrown. Mr. Nakamura used mosses with small, tight foliage. He did not use larger moss such as sphagnum moss except as a brown (dead) protective layer.
Fertilizing
Mr. Nakamura placed fertilizer cakes on his trees after they had broken dormancy and were growing actively. The trees would receive a small amount of fertilizer each time they were watered. Mr. Nakamura said that I could make these cakes by using Canadian rapeseed meal mixed with water, covered with plastic to ferment for one month and then cut into pieces to dry.
During a design discussion about some of my collected trees, Mr. Nakamura suggested that I heavily fertilize the trees to get them into a more youthful condition before I do any serious branch and trunk bending. I think this was just one of the gems Mr. Nakamura taught me.
When asked about fall fertilizing, Mr. Nakamura said that in North America many bonsai people use very little or no nitrogen in fall fertilizers, i.e. fertilizers with a rating 0 - 15 - 14. Mr. Nakamura said that some nitrogen is needed for the phosphorous and potassium to work. He suggested a fall fertilizer of 10 -10 - 10 or 5 - 10 - 10.
Insect control
In the first article of this series, I mentioned that an advantage of repotting is that it reveals insect and disease problems that might be in the soil affecting the roots. In one case I found root-eating beetle larvae and an ant colony.
Borers are controlled by injecting insecticide into the holes with a syringe. Mr. Nakamura uses a Japanese insecticide, Kalhos, that lasts 20 days.
However, I think the key to Mr. Nakamura's insect control problem was this big toad that I came across one cool morning as I watered the trees. The toad looked a little sluggish and dry, so I watered it as well as the trees.
Plant Disease
When I repotted one tree, I found some galls on the roots. Mr. Nakamura used a lighter to heat the tools I had used to disinfect them. Rubbing alcohol can also be used. Mr. Nakamura soaked the tree in a Japanese product, Agrimycin, for 20 minutes after removing the galls.
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