The following article was written by my good friend and fellow bonsai artist Gary Howes. Gary is an enthusiastic bonsai artist and collector of yamadori living in Durban, South Africa. To my knowledge he has the most extensive local experience on an underutilized species which also happens to be indigenous to South Africa.
Before I start I would just like to point out that I am by no means a writer. In this article I hope to cover some of the really remarkable features of Premna Mooiensis aka skunk bush and also the do’s and dont's regarding collecting and aftercare.
There are over 200 species of Premna worldwide, South Africa has 2 of them. I’ve found one so far still trying to locate the second. There are not many deciduous trees that display such amazing characteristics such as deadwood (Jin and Shari), bark and leaf shapes and finally flowers (See fig 2 to fig 5).
Figure 2. Interesting, natural features.
Figure 3. Highly textured bark.
Figure 4. Leaves miniaturize easily with appropriate defoliation techniques. Different leaf patterns are also found.
Figure 5. The Premna also flowers easily.
If one would compare the collecting of say wild olives to Premna there would be no comparison. I cannot simply after collecting flat bottom a Premna with a chainsaw, it does not have the big energy reserves that most olives collected in the western regions of South Africa have. I can only assume that it is the difference between the summer and winter rainfall areas and the very dry, rocky areas where they occur in Natal (See fig 6).
Figure 6. Wild Premna grow in very arid, rocky parts of Natal.
Not even olives from Natal can be flat cut. I have found that there is a very small window between the months of September till the end of October that Premna can be collected successfully, and I base this on 7 years of collecting experience. The best time would be a week after the first summer rains and being a person who lives near the coast this can be quite difficult to calculate accurately.
I live about 200km away from my dig sites which are inland from where I live and the rainfall in these areas differs greatly from the coast. I take every precaution possible when collecting Premna in terms of digging the roots as long as possible and then protecting the roots with moist towels.
The entire tree after collecting is placed in plastic for the long journey home. I have found that no soil remains around the root ball as it is so dry that it breaks off completely, so don’t stress if there’s no soil remaining after collecting.
Once home I only soak the trees in water for about an hour or so no other solutions required. If you leave it in water for any period longer than that the roots split from the uptake of water, thus the cambium splits away from the main root system (See fig 7).
Figure 7. A collected Premna showing roots.
The first collected trees did not survive and I had to scratch my head to figure out what I was doing wrong. The following year I planted my collected Premna back into the ground and it survived.
The question I asked myself was, "What was I doing incorrectly in a potted environment as to what was happening in the ground?" Fortunately for me I was then introduced to a product called Leca thanks in part to Terry Erasmus and Brett Simon. The rest as they say is history.
All our collected Yamadori are now placed into Leca and the results have been amazing. I use the 4mm to 9mm on larger trees and the smaller materials in 2mm to 4mm whole Leca not crushed and I will explain later why not crushed.
All cuts above the surface are sealed off with a proper sealant and all foliage removed. I have never sealed the cuts on the roots but make sure all cuts are cleaned and by that I mean make them look good with no visible damage on them.
What I discovered was that this particular species in order to survive the collecting we had to provide it with the correct conditions to grow. The catalyst was heat and air circulation.
All the material is placed in a shaded, protected area no direct sunlight or wind and grown in milk crates. It must be keep fairly dry as the bark, because of its roughness, holds a large amount of moisture. They will rot if over-watered hence the reason for not using crushed Leca as it retains more moisture (See fig 8).
Figure 8. Good root development in Leca
I have tried growing them in coarse sand and again even that holds too much moisture.
I have tried root stimulant but have not noticed any visible difference in its root development.
Once they have grown sufficiently and built up enough root mass they can be watered normally. You will probably ask well how I know when it has produced sufficient roots (See fig 9).
Figure 9. Fine feeder roots are rapidly produced in the right rooting medium.
Root development starts after the second flush of growth. The first growth spurt is only the remaining stored energy, not the stored energy an olive has; do not be fooled into thinking that you are free to commence normal watering.
It is within this period that they are most vulnerable to root rot if over watered and that is the reason for planting them in milk crates or other well ventilated containers; to allow proper air circulation which promotes the formation of new roots.
The second flush of growth sees a greater extension in growth compared to the first. Once you observe that big extension in the foliage mass occur they can be moved into 40% shade cloth and if the growth continues it can be placed in full sun. Normal, as in every day watering can now commence.
I never fertilize my newly collected Premna for the first year. That is purely my own choice. Because of the vigorous growth I have no need to fertilize within the first year.
I have pushed the boundaries so far with this species and have been able to repot from the crate to a bonsai container within 3 months after collecting (Yes that is correct 3 months after collecting).
In the second year they will be lifted from the Leca and I will first check if it is growing sufficiently before placing into a normal bonsai medium (described below).
Here's the kicker. If within 6 months after collecting a Premna it has not produced that second flush of growth, I can with certainty state it will die.
So let’s get back to my “normal bonsai soil” composition. Growing media or soil is probably one of the most heated topics out there and from my experience mixes differ greatly from grower to grower. My typical Premna soil composition will differ from someone growing the same species in Cape Town as the climatic conditions are different, so please keep that in mind when considering what you will use.
Particle size will depend on the size of the trees being planted out ie larger tree = larger particle.
The mix I describe above is very free draining and is the reason for adding the other 20% aggregate to increase water retention. I experience up to 41 degree Celsius summer temperatures so I have to have some form of moisture retaining capabilities in the container.
In the second planting most of the thicker roots after collecting, if possible, will be removed (See fig 10). I have frequently observed that thicker roots actually die off and are replaced by an entirely new root system consisting of very fine roots.
Figure 10. When planting the second time you may safely remove more of the larger roots.
There is so little information on this particular species and every bit of knowledge gained has and still is trial and hopefully way less error as I learn more about them. This article is in no way intended as a complete or even comprehensive guide to the collection and aftercare for this species either.
Premna have not been used in South Africa in bonsai cultivation however it is to me the most exciting material I've laid eyes on. I've a number of friends in various parts of South Africa experimenting with Premna and we communicate frequently on topics such as cultivation, care and styling. The results we have achieved in a short space of time have been nothing short of miraculous. I am super excited about Premna and hope to continue to build a wealth of information on them to pass onto future growers.
Whenever there is an uncommon or unknown species that can be used in bonsai cultivation there is always going to be a degree of skepticism and even a number a nay-sayers. That will never hinder me. We are blessed in this beautiful country of ours with well over 600 different species of trees, yet we only use about a dozen for bonsai. I find myself wondering why?
I hope that this will be my first of many more articles on Premna and I hope you enjoyed reading my comments. More insights into this wonderful species to follow, look out for part 2.