On September 26, 2017, Bonsai Artist and Instructor Randall Lee of Alameda, California, was the guest demonstrator for the Redwood Empire Bonsai Society (REBS) general meeting and demonstration. Randall chose to demonstrate on how to create a bonsai rock planting.
What I observed first were the preparations Randall undertook for his bonsai rock planting demonstration.
One interesting black lava rock with anchored tie down wires
Several small junipers (Juniperus chinensis procumbens nana)
A variety of companion plants
Plenty of muck (mixed clay and Sphagnum moss)
Sprayer containing water
Various bonsai tools
Randall said various kinds of rocks can be used for rock planting, and that you can usually find suitable rocks at bonsai club shows that offer vendors or at local rock landscape material businesses. For the demonstration, Randall chose a black lava rock that was stable enough to stand up vertically and contained a number pockets and crevices to hold the plants. He particularly liked the rock’s peak or top and the cliff like feature for the front. Prior to the demonstration, Randall anchored tie down wires at a number of locations on the front and back sides. To secure the tie down wires to the rock, he used DryLok Fast Plug, a fast setting hydraulic cement product.
He was ready to layer the muck (a mixture of moist clay and Sphagnum moss). Randall said the Sphagnum moss comes in long strings which he cuts in shorter sections so that it mixes better with the clay soil. He layered the muck to cover the tie down wires and fill the crevices and pockets. Randall cautioned about leaving air pockets, and so he pressed the muck tightly against the rock. He often sprayed the muck with water to keep it moist during its application. Sufficient muck should be made beforehand so that you don’t run out of it in creating your rock planting.
Randall completed the first layer of muck, covering the tie down wires and locations intended for plants. At this point, he placed one of several junipers on the back side near the top of the rock, exposing the branches in the front, like a cascading tree, and some foliage around the rock’s peak. He tried another juniper in the same location, this time there was less cascading of the branches. After getting the opinion of the audience, Randall decided with the latter juniper showing smaller portions of foliage in the front and back sides of the rock. Randall said he had trimmed some of the roots before the demonstration, but that the roots remained long and at different lengths. He checked the position of the juniper a couple of times to ensure it was as he intended it to be, and then he used the tie down wires to secure the juniper to the rock. He pressed tightly a second layer of muck around the roots. He pushed the muck into place to cover the roots and ensure there were no air pockets. Randall added a second juniper and a few companion plants in the same manner.
Randall explained that high mountain plants were placed towards the top of the rock, whereas lower mountain plants were located near the middle to low parts of the rock. Companion plants were added in the same manner.
Once the above was complete, Randall covered all the muck with moss he collected for the demonstration. In the vertical locations on the rock, he used wire staples made from aluminum wire to insert into the moss to hold the moss in place. After a good spraying of water over the moss and plants, Randall’s juniper rock planting was complete.
A raffle was held and member Suzanne Waxman won the juniper rock planting.
For reference, rock plantings by Master Noboru Kaneko are covered in the book “Junipers, Bonsai Today Masters’ Series, Growing & Styling Juniper Bonsai” 2007 by Stone Lantern Publishing, pg. 137.