Article written by Gary English and published on this website with kind permission of The Gardener magazine.
© Gary English gary@cybersmith.co.za
© The Gardener Magazine - Editor: Tanya Visser tanya@thegardener.co.za
Acacia
The most frequent question I get asked comes in the form of “My wife was given a Monkey Tree (Acacia Burkei) for Christmas and now she does not know how to care for it.”, or something similar. I guess an article on Acacia is long over due so here goes.
Acacia are a widely varied species of tree with compound leaves and thorns. Most of them make good bonsai although superior acacia bonsai are rare. We all love looking at acacia trees because they evoke memories of the African bush, and tend to remind us of trips to places like Kruger park. What better way to experience a little bit of the bush everyday than to tend one’s acacia bonsai. That’s exactly why I got into bonsai in the first place, and the beginnings of my own collection were from acacia seeds collected on such bush trips.
I didn’t know it at the time, but growing acacia from seed is the only reliable way to develop this species. The reason is simply that acacia do not transplant well, so digging up an acacia tree in the bush to take home is not only illegal, but pointless. It WILL NOT grow! Leave it there and take home the memory of the tree or some photos to inspire you.
Problems with acacia don’t just end with transplanting, they can be quite fickle subjects, and their tendency to die back after cutting is well known. This can be countered firstly by using clean, sterilized tools, secondly by leaving a stump which will dry up and can be removed the following season, and thirdly by sealing the cut afterward with good sealing paste. These are good practices for all gardening work and not just acacia bonsai.
Another potential problem with some acacia species is their trunks often become narrower as they meet the soil, and instead of creating a nice solid base, one is left with a weedy little trunk with a lovely crown. This is not good! I suspect that this is often caused by bad draining soil that causes the base of the trunk to rot, particularly in the soft wooded varieties. To counter this I avoid watering the trunk directly and water the soil toward the outside of the pot. This is also a good watering practice as it encourages the roots to spread. Also do not allow moss to grow on the bark.
So what’s good about acacia? Well, everything else. They look stunning, and because they are bushvelt trees they grow differently to Northern Hemisphere trees. Throw all those rules like first branch left, second branch right etc out the window. Acacia generally form flat crowns and umbrella shapes to provide shade for animals. Giraffe browse the top shoots to increase the flat crown effect. You must use all of these factors as your inspiration.
Care of acacia:
Acacia must have coarse, fast draining soil as they often have quite week root systems. They must receive as much sun as possible, except perhaps in the hottest areas of the country. Just think of where they grow naturally. They must also get lots of water. Feed every few weeks but use quite weak solutions of plant food. Acacia in the wild actually enrich the soil around their roots, but they won’t necessarily do so in a bonsai pot.
Repotting of acacia should ONLY be done in early spring, just as the new swollen buds are about to burst. They like fairly deep soil.
Constantly prune the new shoots to retain the shape of your tree and to increase ramification of the fine branches and reduce leaf size. Again, this is true for all bonsai.
Acacia tend to loose their leaves at lease twice a season. This does not mean the tree is sick! Often only some of the leaves fall off and the rest just dry up and look old. Remove the rest by hand. In a couple of weeks a whole new set of young leaves will shoot.
Species to look for:
As I mentioned earlier most species make good bonsai, but my favorites are Tortillus (Umbrella Thorn or Haak-enSteek), and Burkei (Black Monkey Thorn).
When buying stock from nurseries pay special attention to the shape of the trunk and only buy a tree that shows character and potential to become a good bonsai. Most nursery stock is grown for planting into gardens, and as a consequence is tall, thin and too straight.