In bonsai tall rock plantings are an interpretation of dramatic natural clifts. The thinner the rock, the greater the impression of height. I was given a gift of an incredibly thin, fragile lava rock. For two years I displayed it in water in a tall glass cylinder. Then it occurred to me it could be the ultimate rock planting in a shallow saucer and an exciting challenge!
PREPARING THE ROCK AND THE "POT"
In June of 2010 I started planning. The rock needed to be solidly attached to the saucer or it would shatter if it tipped over. With three wires taped to the top of the rock to form a tripod to hold it in position, a cement base was created. Two wires went through the cement base to secure the rock base to the saucer.
The Fuku-Bonsai 9" diameter plastic saucer is used as a water catcher for our #8 size potted Living Sculpture or as a saucer (with gravel) for our medium size Hawaiian Lava Plantings. We used standard drill bits to make drainage holes. Shallow containers should have a greater number of small holes instead of just one or two large holes. The four wires that went through the cement base were threaded through four bottom holes to attach the fragile rock to the shallow pot.SELECTING THE PLANT
Because the rock was so thin, I knew that even a small tree would appear large. "Sumo" trees would be too heavy. "Dragon" growing outwards would make the arrangement off balanced so an upright "Roots" was selected. The tree was a 4LL8-R about five years in training. The first photo shows the plant in a 5"x3"x2" pot. The "trunk" is fairly large for this model item but the thickness is still less than the depth of the pot.
The second photo shows the thin lava rock with its concrete base and how the wire is used to attach the rock to the plastic saucer. The plant has been bare-rooted and is being studied as to where it would best be combined with the rock. Keep turning both the rock and the plant to find the best combination.GETTING STARTED
In the third photo, the planting position has been selected and spaghnum moss was placed on the natural saddle and draped wherever the roots will attach to the rock. Nutrient granules are embedded in the moss to provide the needed fertilizer. Note that the coarse drainage media is hipped in the center only.
A large central section of the plant was pruned to create an opening in the root system to fit over the saddle. Using a layer of damp spaghnum moss as a cushion between a rock and the roots of a plant is a standard Fuku-Bonsai procedure that helps the roots firmly grasp the rock. It serves as a water channel to moisten the rock for better growth and to distribute water to the roots that travel down the rock.
Later, the spaghnum moss helps hold granular potting media that will fill any voids between the rock and roots to give the appearance of the roots firmly grasping the rock. Vertical rock plantings dry out quickly so using a lot of spaghnum moss makes proper care easier.
To start the rock-planting, set the tie from the bottom to go over a top branch of the bonsai and pull it down firmly. Then go around and tie the upper roots firmly to the rock. With these two ties, you should be able to safely pick up and lift up the entire arrangement by the plant.
We use plastic ties where it is necessary to have long-term ties and paper covered thin wire for short-term ties. The thin wire will rust and rot off but hold roots in place long enough. With spaghum moss cushioning the roots, most of the roots can be securely held against the rock. Prod some potting media into areas where there are openings and once most of the empty areas are filled, dibble a little spaghnum moss to close the opening.
This must be done carefully to not damage the roots, and especially carefully when you're working with a fragile lava rock!
This is what NOT TO DO! I apparently used too much force to prod media into openings and the lava rock broke! I found that the rock broke off from the base with two additional sections breaking off. I guess I was getting too confident because everything had been going so well!
So what to do? I really didn't want to remove the plant and start all over as the plant really fit well with the top of the rock. I decided to protect the part that was complete with aluminum foil and build a wire frame to keep all into position until new concrete could harden. A few days later, I took off the wire support and completed it.
Finishing was done very carefully. First a collar was made with aluminum foil folded over several times to be fairly stiff and about 3" tall. The ends were folded over until it was about the right diameter and it was positioned around the base of the rock-planted tree.
Equal parts of coarse and body media went between the rock and collar and dibbled in with a chopstick. The temporary aluminum foil that protected the top section while the cement was hardening was removed and a wide aluminum foil went around loosely, firmed up for the bottom 3" with additional media added until it was filled between the bottom 3" and to near the top.
A layer of spaghum moss and the top of the foil flaired out a bit allows water to easily penetrate the column. The foil was firmed up and masking tape wrapped around helped to support the foil column and additional media filled the shallow saucer.
When thin vertical rocks are used in bonsai interpretations of dramatic cliff scenes they especially work well when used with shallow display trays.
later in November 2010, the tree seemed to be doing well and
branches were all pruned and additional nutrient granules added to
the top of the aluminum foil column.
Five additional months later in April 2010, (10 months after the rock planting), the aluminum foil removal began from the top. Roots seemed fairly well established and had travelled down to the pot. Very carefully, the pull down plastic ties were removed along with excess media to expose as much of the rock as possible.
New paper covered tie-wire positioned roots in their most attractive position and additional media and nutrient granules filled in where any hollow spots were found. Spaghum moss was tucked into tiny openings so roots appear to tightly hug the rock. The tree seems to be growing very well.
Most branches that were shortened in November have resprouted and three or four new growth points have replaced each branch that was pruned back. While the trunks and roots will enlarge over time, the foliage crown of the tree can be kept very compact.
CREATING A LONG-TERM STRATEGY
Right now, the tree is about the right size. But the tree will continue to grow and thicken while the rock will stay the same size. It is important to consider this in tropical bonsai rock plantings. In my earlier days, I planted ficus bonsai on rocks and as the tree grew and roots thickened, over the years, it spread to completely cover the rock that can no longer be seen! So there should be a conscious effort to continually remove smaller new roots to keep portions of the rock exposed. It's also important to plan for cutting back heavily from time to time and to create strong branching growth close to the trunk. This will allow you to cut back hard to keep the crown in scale with the pot and rock.
The plant and rock will remain permanently in this saucer. From time to time, if root rejuvenation is necessary, much of the potting media in the shallow saucer will be removed, roots cut back, and new media added without removing the tree from the pot.
Shortly after these photographs were taken, new aluminum foil was placed to protect the roots in the shallow pot that are still weak. When rock planted 10 months ago, there were no roots within 3" of the saucer. The photos below show the growth in Hawaii's ideal growing conditions but; even here, the roots will need some protection for another year or so.