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"Rhizotonic" by UK manufacturer Canna.
There have always been various chemicals and potions offered to the bonsai enthusiast, the vast majority having negligible effect on our bonsai, at least when compared to the use of solid horticultural practice (use of open soils, root-pruning, good positioning and watering). However, one product that came to my attention last year has proved itself to have, without doubt, a major positive influence on bonsai cultivation. Called Rhizotonic and made by a British company called "Canna".
Revival of a Juniper Itoigawa bonsai during 2015.
Throughout the growing season of 2015 I used Rhizotonic on a number of weak-rooted trees (see the Itoigawa Juniper above), or tree species that can be difficult to transplant such as Sabina Juniper and Cedar. Despite the manufacturer's claims that the use of Rhizotonic aids and increases the volume of root-production, the successful recovery of these trees could not be directly attributed to my use of their product.
Rhizotonic is described by the manufacturer as "..........a powerful, algae based, vegetative stimulator for plant roots. It contains multiple vitamins and is 100% natural........adds more than 60 microbiological substances that considerably speed up the growth of a balanced root environment." (Taken from the Canna website).
Aerial roots on a yamadori Hawthorn.
Where I started to really believe the manufacturers claims was during the Winter of 2015 and 2016. During this time I collected a number of very old Hawthorn (Crataegus monogyna) yamadori that, as per normal, were kept in a frost-free, humid environment. The trees were watered (given a soil-drench) twice a week with Rhizotonic at the recommended dose. During February, at the time that Hawthorn normally begin to emerge from dormancy, I noticed the appearance of aerial roots above soil level. In some cases near the top of the trunk!
As anyone who has tried to airlayer Hawthorn will know, Hawthorn are reluctant to put out adventitious roots and so the appearance of 20-30 root-tips all over the trunk of one Hawthorn in particular was something of a shock. Certainly, I have collected many Hawthorn over the past 15 years and this is the first time I have seen them root so prolifically. At the time of writing, that I have 20 Hawthorn issuing these aerial roots leads me to ascertain that the only difference in my care regime this collecting season has been the use of Rhizotonic.
Another example of strong, adventitious roots appearing on a newly collected Hawthorn trunk.
A third example of a newly collected Hawthorn with a combination of red adventitious roots and green shoots emerging from the top of the trunk.
The appearance of aerial roots is all well and good but it is heavy rooting below soil level that is pertinent to the survival of these trees. Here is an example of a well-placed adventitious root appearing at the base of the trunk of a 4th Hawthorn.
This phenomenon does not seem to just apply to Hawthorn. I also have a Blackthorn, notoriously reluctant to root even below the soil surface, issuing aerial roots. Anecdotally, other bonsai enthusiasts have reported the same occurrence on Blackthorn after the use of Rhizotonic.
Adventitious roots emerging on a healthy, recently root-pruned specimen Acer campestre bonsai.
In early March 2016, having seen the positive effect of Rhizotonic on newly collected trees, I began dosing newly repotted, and root-pruned, specimen bonsai twice a week at the recommended dosage. Within 3-4 weeks, this Field Maple (Acer campestre) began sprouting adventitious roots directly from the base of the nebari, an extremely useful effect when trying to improve the surface roots of any bonsai.
It should be noted that the Field Maple had been kept outside in my garden since root-pruning, and had not been kept in a warm, humid polytunnel as had the yamadori Hawthorn. But it had still produced these new surface roots, at a time of year that they are wholly unexpected. (I have witnessed the appearance of surface roots before on Acer species in general, but this tends to be during late Summer when heavy root-production is normal, and not in early Spring).
My conclusion to these events is that without doubt, the routine use of Rhizotonic on newly root-pruned, weak or newly collected trees is extremely advantageous to successful rooting. After showing the appearance of the aerial roots to other bonsai enthusiasts on Social Media, it would seem that those who have used Rhizotonic have also had great results on their trees.
One word of warning: Rhizotonic is fairly easily obtained through a number of online stores. But there have been stories of a few unscrupulous sellers diluting the solution with water and keeping back a percentage for themselves, so reject any newly purchased containers that are not fully sealed!