Friday, October 12, 2012

Experimental root over rock/root clinging to rock technique.

When planting bigger rocks with Ficus using the normal wrap method watering became a problem ...and burying such a large rock is out of the question.

I am experimenting with making a removable (the roots can be inspected without too much disturbance) covering for the rock with a watering area. You will also notice that I am doing away with the normal "rock in a bonsai pot" by giving the rock it's own base- almost " a rock on slate".

More or less what I envisage for this planting:

Here is the technique:


The rock is set in a product called ROCKSET. It hardens very quickly and it is really as hard as rock. Because it is quite heavy it will keep the big rock upright. To make it look like natural rock it would be possible to sculpt it - will experiment on this later on. The base can be fastened to a pot by leaving some holes into the Rockset and wiring the base onto the bonsai pot. For this planting I am not going to put the rock into a bonsai pot. Soil will be slanted to the rim of the base. Rockset can be colored by using oxides.


Using old newspapers and boiling water make a paper mache. This will be used to line the rock The lining must be about 1cm thick. At the base the lining will slant from thick to very thin to the rim of the base.


Lining the  rock. Crevices are filled thickly and outcrops lightly. This is important because this will force the roots to grow as close to the rock as possible. The backside is not lined because Ficus in nature normally grows only on the one side of a rock cliff. The lining finished:

Notice that the top part is not covered. Ficus never grow over the very tip of a rock but rather on a "cliff" lower down. The "lip" of the covering can also be formed by the newspaper mache- this will ensure that watering your root over rock planting will be simplified.

The mache on the side must be very thin otherwise the mould will not seal of nicely there:


The mache is now covered with a product called PU-FOAM (Spray polyurethane foam, commonly referred to as SPF is a spray-applied insulating foam plastic that is installed as a liquid and then expands many times its original size.)

My first attempt was an "overkill" because I tried to cover the whole area in one go. It would be better to do it in layers starting from the bottom letting the first layer dry before applying the next. Laying the rock down in sand overcome this problem:

One can of the foam will be enough to cover 5 to 6 rocks depending on the size of the rocks. To prevent the foam clinging to the sides of the rock or the base, it can be wrapped with cling plastic before applying the foam.

When dry the cover can be lifted from the rock and refined by using a sharp blade. The outside must be painted by an oil based paint to protect it from the sun.


Remove the newspaper and do your rock planting as usual. Here is a pic of me and Roberto struggling to set all the roots into the little crevices:

Luckily the roots were long enough to reach the base of the rock.

When finished fasten the covering to the rock by using cable ties. When done pour in your DRY soil medium. The rock and covering can be tapped lightly for the soil to settle in all the crevices. Water heavily. Watering the dry soil for the first time may take a while.

Here is the finished planting two weeks later:

Notice the watering area:

I have added some dead moss to encourage  more roots.

The back side:

Cable ties and off cut foam pieces were used to force the current roots into the crevices.

I will open the planting end February 2013 to see what is going on. I expect not to see a lot of top growth but a lot of root growth- it's the habit of Ficus natalensis to grow a lot into it's roots in the beginning.

Will update then.

To do the normal root over rock the whole rock can be covered and after it has dried it can be cut in two halves.

The tree end December 2012:

It has grown very well and I am very curious to see the roots!

March 2013:

I should have opened the tree because I forgot I used a cable tie to keep the three trunks together to hold them together for the planting. The tree has grown so fast that it's trunk started to grow over the cable tie. It left a scar but it will heal over time. The three trunks have also fused and I got some roots going where the damage was done - not all is lost.

There are a lot of roots coming out of the bottom of the planting- the only other worry I have is that there is a big possibility that some roots may have grown into the styrofoam. With Ficus roots everything is possible. It is Autumn here so I wll have to till early summer to open the planting.

Can't wait!

The waiting is over!

I could have wait for another month but our weather is warming up and most of my Ficus started  growing again.

This is the tree today(August 2013) - 11 months later:

I got tremendous growth on the tree in comparison with my other Ficus the same age. I think that the roots was kept warm by the foam and it added to the high growth rate. The cover came loose quite easily - only a few roots grew into the covering. Here is the first view after removing the cover:

I got a lot of fibrous roots - I was a little bit worried that I would get only or two of the original roots fattened up. The grey you see in the picture is leftover newspaper that I used to line the rock to prevent the foam from sticking to the rock - it disintegrated in total. Some of the organics in the soil mix disintegrated also - most of the roots that formed looked more like air roots than roots growing in soil.

Here is the roots after I washed off the growing medium:

In general I am very happy with the roots that have formed. After rearranging some roots I fastened them again using cable ties and foam:
I also cut back the tree a bit. I replaced the cover:
I did not fill up the cavity after covering it up - I will give the roots a day for any damaged roots to seal off.

The tree will be left alone to grow freely again - I will open it up in January to prevent the cable ties to cut into any of the roots.

In general I am very happy with the outcome of the experiment.

I am removing the cover bit by bit to harden off the roots:

The tree February 2014:

The three roots going straight down were not part of the design. They will either be removed or rearranged.

The tree will be left like this until late spring 2014.

5 December 2015:

I have not worked on the tree for over a year now.

Lots of development in the roots but not much to the top. The cuttings have all fused now into one trunk. The variety I am using is quite amazing when it comes to fusing and root over rock.

I was planted in a home made Rockset pot but the pot could not handle the weight of the rock and the roots of the Ficus - so it is back into a plastic basin again.

I need to do some branch selection and rerouting some roots soon.

Wednesday, October 10, 2012


Rustenburg Bonsai Kai organized this meeting and it was a big success.

Some of the trees:
 Small trees-30cm and less.

 Small trees-30cm and less.

Small trees-30cm and less.

 Bigger trees - 30cm and bigger.

Bigger trees - 30cm and bigger.

Bigger trees - 30cm and bigger.

Bigger trees - 30cm and bigger.



Small trees-30cm and less.

Miniature Pomegranate




Japanese Maple

Bigger trees - 30cm and bigger.

Some examples of strangler style Ficus in different stages of strangling the host by Mack Boshoff used in his demonstration:

Victory stage

Dying of host stage

Beginning to strangle

Overwhelming the host with roots

Host still looking healthy