This is a type of lava known in Hawaii as "Welded Splatter" or "Red Cinder."  It forms far from the volcano's summit along the lower rift zone. At these lower elevations,  the lava temperature has cooled, it has thickened, and blobs are thrown up for shorter distances. The lava plops and builds up "splatter cones." These softer forms of lava are used by Fuku-Bonsai for its Hawaiian Lava Plantings in which the rock substitutes for a bonsai pot.  But for "Root-over-rock" plantings in which roots grow into the media in a pot,  we do extensive sculpturing and generally like to create rock plantings in which the rocks are positioned vertically. 


                 There are two basic schools of thought when it comes to rocks for bonsai. Many believe dense hard rock should be as natural as possible without any manipulation or sculpturing. They use the rock just as it was found.  With these limitations, there are very few natural rocks suitable for bonsai. Some forms of lava are very dense and cannot be carved.  We may join two or more pieces together to create formations and/or mount them so they are positioned as attractively as possible. Whenever I am lucky enough to find such a rare natural attractive rock, I use them as naturally as possible with any cement colored to match or at the base where it will be covered with the potting media.  Relatively soft porous  "Welded Splatter" is the material we are using to teach root-over-rock techniques to our study group members.  It is more easily shaped and these are the principles used.

FIRST EVALUATE THE ROCK  (See photo above and two photos below)


          Three views of the same "Welded Splatter" rock.  The rock used for this article was originally about 14" long x 12" wide x 8" deep and weighed about eleven pounds.  The top of the first large photo shows that a cinder blob is still attached to the main piece.  These pieces are created when bulldozers take apart old spatter cones and the material is used for fill, for grading and road work,  with a tiny portion used for bonsai.  The above left photo shows that cinder blob facing forward and the third photo shows a composite of welded splatter.  The blob is not well attached so the first task is to remove it in one piece which is relatively easy.

          With a metal pick the connection between the blob and welded splatter was cleaned out and with a stone chisel and rubber hammer, the blob was knocked off. 

         With the metal pick, I attempted to trim a section off the bottom to allow the rock to stand up.  But although that section came off,  an additional section of the rock broke off.

          So I trimmed the bottom a second time and ended with a smaller main rock in a vertical position below.  The highly textured blob and the broken off bottom will be used in a different way.        


                  The cliffs on the windward side of the island of Oahu formed an impressive backdrop for the town of Kaneohe where we purchased our first home in 1962.  These were my bonsai formative years. As a beginner, I was asked to teach, became hooked, and learned my basic bonsai skills until 1973 when our family moved to the Big Island of Hawaii to form Fuku-Bonsai. 


                  Imagine sections of steep cliffs with slopes flattening out to create dramatic scenes! The cliffs are formed by water erosion and during rain storms, become a series of waterfalls that cut steep, deep, small valleys, with multiple "saddles."  It's not hard to imagine a steep cliff section with slopes in a bonsai pot!

                 The Beginner Study Group starts with three Introductory Workshop Packages and a few unlisted complimentary items not generally available.  The first Sumo workshop teaches basic potting techniques.  The second Roots workshop teaches how to extend the roots straight down as a preparatory step for a future workshop to create a larger taller Roots bonsai, or to use for a larger Root-Over-Rock bonsai. 

                  We supply a small vertical rock and the major challenge is to sculpt it to add a saddle and root trail crevasses.  This was described in Lesson #8 posted at Upon planting it as the third Roots-Over-Rock workshop,  a small 2" plant transforms into an envisioned Sumo type banyan perched on a cliff with roots dropping straight down in a dramatic tropical scene! That's an ambitious goal for the third bonsai for a beginner!   This lesson is to aid those in the Fast-Track Study Group that will be planting a 4LL8-Roots on a larger rock.  That also is an ambitious challenge!  I used a large rock and an older plant to be able to explain concepts and techniques.  Here's how. 


           The photos below show the same rock from different views with the roughly shaped rock on the left and the more sculptured rock on the right to see the amount of sculpturing during this second phase.  To this stage, all work was done with the metal hand pick. 


             In the above "before" and "after", one side had a taller pinnacle section and with a pick,  "valleys" were carved.  Whenever there was a rock section at the base of the valley, it was made into a saddle the split the "waterway" to either side of that saddle.  Try to create as many pinnacles as possible and that will give you multiple "root trail crevasses!"


              If the rock is rotated about 45° the second right side view of the rock actually has a different character with a lot more porous air spaces.  By trimming and creating multiple pinnacles,  you'll automatically create valleys that run into smaller pinnacles that split the waterways to form "root trail crevasses" for the roots to follow down to the media in the pot. 


               This third view is the "top side" of the rock with a lot more swirl and surface texture.  Generally this side is very easy to sculpt as the surface is continuous and holds together.


             In this fourth view, the top of the rock lacked an interesting profile and that was the start of the sculpturing to first create the initial pinnacles.  This led to valleys,  then to  root trail crevasses.  So in a sense, the rock suggested how the final shape would become.



                  TWO ADDITIONAL VIEWS OF THE SCULPTURED ROCK:    Notice how there is a different appearance when you change your viewing position!  This is the higher standard we try to attain. A lot of it depends upon the inherent quality of the rock used and not all rocks of its type are the same!  The character of rocks at each splatter cone is different.  We work with the land owners and the quarry managers to get access to the best possible rocks and hand select each one.  This type of rock have irregular layers of harder materials and it takes a while to be able to "read" the rock.  But by getting it to sit into a vertical position,  the sculpturing of each side is influenced by the traits of each side. 

                  The original rock weighed eleven pounds.  The three removed larger pieces weigh about 4.5 pounds and a total of about  2.5  pounds of dust and chips resulted in the sculptured rock weighing just four pounds to this stage. 

                    TOP VIEW OF THE ROCK.   Note that although our sheer Hawaiian cliffs are all lined up in a panoramic cliff wall,  our complex vertical rocks are sculptured so that an interesting profile made up of pinnacles is developed first.  Then on each side,  valleys are created and when you hit on obstruction, create a lower pinnacle and split the root trail crevasses.  So almost automatically you produce a rock with interesting attractive saddles and you could plant as many smaller plants as you have saddles!

                    On larger complex rocks, it will look okay if you plant only a single plant and the selection of which saddle to use is sometimes the major challenge.  The idea is to leave the most attractive rock features exposed and to plant where the roots will cover over the least attractive parts of the rock!  Too often when a person finds a rock with a depression,  the immediate impulse is to plant in the depression.  In doing so, you cover over what makes the rock interesting!

                   Sumo-type trees with heavy or multiple trunks, low branches, and heavy crowns are ideal for flatter rocks like our Hawaiian Lava Plantings which was our original specialty.  Trees tend to grow stout with these characteristics when grown on rocks and so we mastered Sumo styling first.  Smaller, younger sumo bonsai can be rock planted on these taller complex rocks, either as a single tree or multiple trees.  But there may be problems if you try to rock plant older Sumo-type trees as the surface buttressing roots grow outwards and are just too stiff to bend into the valleys! 

                   Because of this we pre-train older Roots bonsai to be rock planted on taller complex rocks.  Sumo, Roots, and Root-Over-Rock use similar concepts and the members of the Beginner Study Group start with these three workshops.  Sumo teaches basic potting.  Roots teaches how to prepare trees for future training for larger Roots or Root-Over-Rock bonsai.  Root-Over-Rock is an ambitious third bonsai for beginners but if they can meet the challenge, all things are possible!  The first half of the workshop is sculpturing the complimentary rock.  This may take several email exchanges to understand and produce an acceptable rock ready for planting.

                   It was a bit hectic and I wasn't able to get back to the project for a day.  In that time, I selected the tree,  removed the foil collar and had studied the roots. I was confident there were more than enough strong roots which is the key to this type of taller rock planting.  The actual planting uses special techniques but is usually easier than sculpting the rock. 


                  When doing custom rock planting,  the rock determines the type of tree to be used. If you review the last several photos,  you'll notice that although the inspiration were vertical parallel cliffs,  in a few views, the rock really has a more interesting slanting orientation.  For slanting rocks with jagged lines,  I tend to pair them up with Hawaiian Dragons.

                 I happened to have a demonstration tree from an advanced workshop that extended and twisted the roots of a 8LS8 Dragon that was up-potted with a #17 Conversion Kit into a 17"x12"x2" oval pot.  It had been done a year or so ago and upon removing the aluminum foil collar, found the roots had developed well.  With so many roots and root trail crevasses,  the tree should quickly establish on the rock.  Years ago I trained a dragon on a jagged rock and it came out very interesting and was given the name:  "HAPPY LEAPING DRAGON!"  Since then several variations were made and this would be another.

         The rock was detailed with a drill with a 1/2" masonry bit. I leave the parts that will be exposed as natural as possible but bore out excess rock within the "root trail crevasses." This lightens the rock a bit and provides opportunities to "stash"  large amounts of Nutrient Granules™."  This is a rare "non-water soluble"  fertilizer which is an invaluable trait as it proves long-term nutrients "on demand" and will not burn the roots.

         All root trail crevasses are lined with sphagnum moss,  body media, more moss, and more media with the roots pushed to the outer visible parts.  The roots are just below the visual "surface" of the rock, but as they thicken, they will appear to hug the rock.  The more you dig out the the root trails, the better you can create an attractive  hospitable environment for the roots. 



          By using a heavy sphagnum moss layer to line all "root trail crevasses"  you're actually creating an internal watering system,  especially if you put an extra amount near the top and keep it exposed so when you water, use a turkey roaster baster to get water flowing through the sphagnum moss to travel behind and under the roots which will visually cover the crevasse.   I like to lay the rock down as it's easier to add the materials. If there's a hole through the rock, plug it with some sphagnum moss or a piece of pumice.  Sphagnum moss, Nutrient Granules,  body mix, sphagnum moss, Nutrient Granules, body mix in layers until almost filling the crevasse.      

          Start at the top and build the cushion on the saddle first and when all crevasses filled, position your plant and distribute the roots into the logical root trail crevasses.   With bindwire pull down the plant tightly into the saddle.  Make any root corrections and use bindwire around the rock  to keep roots tightly in place.   Arrange the roots on one side of the rock, temporarily secure them with bundles of crumpled newspaper and foil, turn the rock over and work on arranging the roots in the crevasses on the other side.   

          The original rock was 14" long and eleven pounds.  It is now 11" tall and just 3.5 pounds!  A photo sequence with additional information follows:



         The materials and supplies:  Hawaiian Dragon with extended roots about 15 years in training,  sculptured rock, bindwire, sphagnum moss,  body potting mix,  Nutrient Granules,  and 12" diameter shallow 1:10 Project saucer pot with holes for attaching rock with pre-positioned wire. 

          The tree barerooted and roughly arranged on the rock with the original 17"x12"x2" oval pot and removed media behind.  While it is possible to pot a tree with shorter roots and grow the roots down to the pot,  it is faster and better to have longer roots created first that will reach the media in the container.
          Lay the rock on one side and add a generous amount of Nutrient Granules in each "root trail crevasse."  Cover and line all sides of the crevasse with sphagnum moss,  body media mix, and dibble in place.  Add more sphagnum moss and body mix until the crevasse is almost full and add a thin layer of sphagnum moss and it will hold most items in place.  Place crumpled newspaper over the surface and a few sheets of folded newspaper to cover.  Pat down, grasp and turn over to work on the other side.
         Repeat preparing the rock with Nutrient Granules, sphagnum moss, and body media mix.  Dibble it into the area of the rock that was bored out with the masonry drill.  I tend to take out a lot as long as I feel the rock will not break.  The roots will be largely going down and not likely be pushing outwards and break the rock apart as when planting totally in the rock.  For this reason,  "root-over-rock-into-pot" is a superior system compared to simple rock plantings.  From time to time, the media in the pot can be rejuvenated so there is a better potential for a long-lived tree to enjoy and improve into the future.
          View of first placement.  Roots were roughly positioned and bind wire went around to hold all in place while making adjustments and guiding roots into position.  Because the roots are long enough,  this is fairly easy to do and the tree will very quickly establish on the rock.  Within six months, the roots will be well into the pot. Within a year or two,  the roots will be well established in all parts of the rock.  Extending the roots first is a preferred method compared to planting a small tree on the rock and waiting until the roots grow down the rock into the media in the pot below. 
          Using bindwire, pull the tree tightly down into the saddle with the wire going under the rock,  doubling if necessary.  Tie over each root trail crevasse, going under the rock.  Position all roots,  then go around the rock several times with bindwire.  This allows you to tie vertical and horizontal wires together to tighten as well as to create a wire netting wherever needed to hold roots in place.

        Note that in this case,  the lowest branch was pulled down tight and a horizontal wire tied it to have that branch snuggly down against the rock, then growing out. The attached aerial root was blended into a root trail crevasse.  The area between the rock and the tree trunk was filled with sphagnum moss, Nutrient Granules, and body mix so it appears like the tree is lying across the top of the rock. 

       The use of thin paper covered bindwire works well as the wire will rust out in a few months while bonsai aluminum wire will bite into the roots.  Bindwire is not readily available and we supply our study group members with a small amount from our spools. 

         Starting from the top,  stretch all roots in position and dibble the sphagnum moss into the root trail crevasse.  Pour some body media on the working surface and use a tablespoon flattened with the sides bent up in the shape of an "open funnel." Use it to scoop up and hold body media that is dibbled in place. I use a carved piece of bamboo for larger areas and a steel dibble for smaller areas.  The idea is to get the material behind the root to fill that crevasse which pushes the root to the outer surface where it is held in place by the bindwire netting.  The larger your root trail crevasse the more sphagnum moss, media, and Nutrient Granules you can deposit and the better the future growth. 
         Once the top portion is filled and roots arranged,  lay the rock on its side so it's easier to pour media in place and quickly dibble into openings to assure there are no air pockets behind the roots.  Note that the roots are longer than needed and all such roots are trimmed even with the bottom of the rock.  Filling all the loose areas is very time consuming. Probe with a thin dibble and compress loose areas into compacted sections with a larger open area, then fill each of those areas,  closing up the surface opening with sphagnum moss. Note  that tie-down wires were positioned through holes made near the bottom of the rock,  then coiled out of the way until planting is almost complete. 
            This photo was taken as the planting was being completed.  The rock positioned on the pre-marked area,  and a wet towel wrapped around the rock and roots for work to resume the next day.  In this type of work,  I usually have the body mix right on the table,  scoop it up with the "open funnel spoon" and pack with the carved bamboo dibble.  The sharp metal dibble works well to place the sphagnum moss. 
          The bottom of the shallow 12" diameter x 1.25" deep 1:10 Project saucer-pot has a large number of 3/8" holes drilled through the bottom.  When using shallow pots, be sure that there are enough drain holes,  especially in the central area.  We came up with this design and use a drilled saucer as the template to drill the next one.  It drains very well and much better than the shallow oval ceramic trays that may have only two larger drain holes. 
          Completing potting is simple.  Coarse bottom is banked up against the rock along with Nutrient Granules at the base as shown on the left side.  Then body mix is added and banked up against the rock as shown on the right side of the pot. 


         Note that the planting was designed to create three views with each of the three saucer legs serving as a "front."  True Indoor Bonsai recommends the use of round shallow pots whenever possible.  This saucer is 12" diameter x 1.25" tall.  The shallow saucer-pot allows the rock and tree to stand out.  In a deep heavy pot, the rock planting would not have the same elegance. 

         Trees must be turned to grow evenly so shouldn't all sides be attractive.  Which of the three views is your favorite? 


           Creating a 1:10 Project with a shallow saucer-pot is challenging because the very gravelly media would quickly scatter if watered with a hose.  We firm up the surface by first scattering a layer of finely chopped sphagnum moss as seen on the left side, and sprinkling some coffee-grain size fine top dressing over the sphagnum moss and flattening it down with a spoon. This will be quickly colonized by fine root hairs which are followed by larger roots to be followed by still larger roots.  Once these roots form (in about a year or so), the foil can be removed and the roots will hold the shape.
       The foil should be 3X the 12" saucer diameter or 36" and it was crumpled then positioned.  I start in the middle where there is the most surface and line up the edge of the foil just inside the rim,  pressing the foil down to the rising surface until I reach the rock.  Continue in both directions until you get behind the rock,  overlap and join the two foil ends and finalize the foil to press down on all soil surfaces.  Using thin monofilament tape,  and starting at one of the three legs, tape over the foil to the second leg, go under the saucer to the third leg, come over the foil back to the first leg, then under the saucer to the second leg, then over the foil to the third leg to complete taping down the foil. 
         Position the vertical foil about 1/4" away from the rock surface and add a small amount of body media, skipping areas where the rock is exposed. Do about 2" all around and press in the foil,  positioning the next 2" about 1/4" away from the rock. If done properly, there will be a thin 1/4" layer of media wherever there are roots, but none where there's exposed rock.  Roots stay in the root trail crevasses and will generally grow down and not horizontally around the rock under the foil.  There's a tendency to add a thick heavy layer, but this will not produce roots that tightly hug the rock. Only a thin layer is recommended.  


         With the foil collar complete, use thin monofilament tape and very tightly force the foil against the rock planting.  Run the spiraling tape about 1" apart and make it as tight as possible.  This will flatten the roots to give the appearance that the roots are very strongly grabbing the rock instead of going round and sitting on the rock surface. 

         Make air holes every inch.  If you see roots dropping outside the foil, it usually means that the roots inside the foil is either getting too much water or not enough air or both.  If that happens, create more air holes.  In this type of application, the foil can be removed in 6 months or so starting from the top.


              A vertical root-over-rock planting is much more complex than a simple rock planting into a cavity created in a rock.  First the rock must be stabilized into a vertical position and that generally means trimming the bottom and flattening by rubbing back and forth on a sidewalk or hollow tile block.  Then create a saddle where the bottom of the trunk will sit.  For a vertical rock planting, the roots should preferably be pre-trained to generally grow downwards and preferably the root should already be long enough to reach the surface of the pot below. 

             I try to create the maximum amount of "root trail crevasses" to be able to accommodate all possible roots. Generally its best to rock plant semi-trained trees on rocks that are growing vigorously.  It is a lot more difficult to train old mature bonsai that are growing at a much slower rate. 

             This example showed a rock that was relatively soft and easily carved.  It started as an 11 pound rock and ended up just 3 1/2 pounds before rock planting began.  It's my opinion that if you're going to try to create a vertical rock planting,  it needs to have an elegance and not have a huge bulky appearance.  To finding the ideal rocks become very important.  But with so few ideal beautiful natural rocks,  it may be more productive to learn to sculpture common rocks. 

             When all is said and done,  it's the final results that counts.  It doesn't matter how it was done.  It's going to be judged by various standards and it may not be nice to everyone.  But if you are the creator, the main thing is that you are happy and satisfied with your effort and that you did your best!  Bonsai is a wonderful but challenging journey!

       ©   Mid-Pacific Bonsai Foundation and Fuku-Bonsai, 2013