There are numerous types of decorative mini trees. We show how and when to prune bonsais correctly and what to look out for in the different shapes and varieties.
Cutting a small tree as a bonsai – the Japanese art form of tree design needs to be learned and has its pitfalls. But even beginners can learn how to prune correctly. We will teach you the basics, i.e. everything you need to know about the first cut, about care, leaf, and root pruning, and about when it is time to cut back the bonsai in the first place. Following this article, you’ll find useful instructions for three popular bonsai species.
Pruning Bonsai: Basics
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When pruning bonsai, a distinction is made between maintenance pruning and design pruning. While maintenance pruning only maintains and refines the existing shape of the bonsai, design pruning serves to educate the small tree toward its picturesque form. Both are done by hand, as neither a small indoor nor a large garden bonsai should ever make the acquaintance of hedge shears.
A common misconception is that bonsais are special dwarf forms of their larger relatives. In fact, however, they are just normal plant varieties that are kept small by small planters and just the right amount of pruning. The biggest problem to overcome is always apical dominance. The Latin word “apex” means the tip of something and apical dominance means the stronger growth of the shoot tips.
This growth behavior is very important for woody plants in nature in order to grow quickly in height and width, to be able to absorb sunlight over as large an area as possible, and not to be shaded by adjacent competitors. The targeted suppression of apical dominance makes it possible to create tree miniatures that have an apparently natural growth habit.
When and how often should a bonsai be pruned?
Design pruning is only done when the shape of the bonsai is to be redefined for the first time, or even after the fact. Because strong branches are removed and over-wall cutting is a major effort for the plant as well as a loss of water, design pruning is done only as needed and in early spring before leaves emerge or in late fall after leaves have fallen – the same times apply to evergreen plants. In addition, design pruning should be limited to only one pruning per year.
Maintenance pruning is used whenever new shoots have emerged, i.e. very regularly and – depending on the plant species – virtually all year round. Pruning consistently removes shoot tips that would otherwise suppress the growth of lower-lying shoots due to the aforementioned apical dominance. Regular maintenance pruning ensures uniform, dense growth – not only at the top but at all levels of the plant along the shoot axis.
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The correct procedure for pruning bonsai
Not every pruning goes the same way. We explain the procedure for maintenance pruning and design pruning in great detail below.
The maintenance pruning of bonsai
Regular maintenance pruning is the real reason why bonsai foliage can be kept in the miniature form of itself. It is possible and necessary during the entire growth period of the plants. Using pointed, sharp bonsai scissors, periodically cut off only the tips of newly grown shoots one at a time. You can also remove entire new shoots if they do not fit into the overall picture.
But be careful with conifers such as Pinus (pine) or Larix (larch): with them, you do not cut with sharp scissors, but “pinch”: Using tweezers or pointed fingers, the tip of the shoot tends to be twisted off or torn off, because the use of scissors leads to brown needles and is poorly tolerated by the plant.
It is important that really only the soft, freshly grown shoot axes are removed in the maintenance pruning – larger pruning actions are rather postponed to a suitable date for the design pruning.
The design pruning for bonsai
Shape pruning, in combination with wire, forces the woody plant to grow into a bonsai into the shape desired by the designer. Bonsai produced from seedlings or cuttings are subjected to design pruning for the first time only after a few years of quite normal growth – when they also move into their relatively tiny bonsai shell. Now the future bonsai also comes into contact for the first time with special soil for bonsais, which was not necessarily necessary before. This first pruning, as well as all subsequent design pruning, is usually carried out in early spring or late autumn, and in no case more often than once a year.
Even decades-old, tall wild plants can be turned into picturesque garden bonsai with gentle handling and annual design pruning. Strong branches are also removed during the shaping process. To promote over-wall healing of the resulting wounds, it is important to work neatly with the proper tools – concave forceps if possible – and to use a wound closure paste.
When designing your bonsai, your individual creativity is called for – you determine what shape your work of art will later have. Deciding which branch to keep and which to remove is not always easy. Therefore, we have listed a few important basic rules for design pruning for you to follow.
- First, remove all dead branches and twigs, as well as disturbing dead foliage, in order to have a clear view of your little tree.
- Vertically growing, strong branches that cannot be corrected even by tying them down and wiring them must be removed.
- If two branches spring from the same trunk at the same height, choose one and remove the other.
- Remove one or more branches if they cross.
- Leave thicker branches at the bottom than at the top – this will create a natural-looking crown.
- Now remove any branches that you feel do not “fit in” – always keep in mind the view from all angles to get an all-around aesthetic shape.
Tip: Cut bonsai roots
Quite a few bonsai experts advise that after a design pruning, the roots should also be shortened. This seems logical because otherwise, the plant will strike out all the more after the design pruning in order to restore the correct ratio of root and shoot. However, if the roots were reduced at the same time, this reaction will be somewhat slowed down. In any case, it makes sense to perform the design pruning together with the obligatory root pruning when transplanting. By the way, of the utmost importance when repotting bonsais is the use of suitable special soil for bonsais. This provides a balanced supply of water and oxygen to the plant roots so that they can grow optimally and remain healthy.
The right pruning for each type of bonsai
To give you a good orientation, we present three types of bonsai and the appropriate pruning techniques. For this purpose, we have chosen a houseplant from warm climates, a conifer, and a deciduous tree.
Pruning ficus as a bonsai
Of Fig (Ficus), several species can be grown as bonsai. The following applies to all of them: if you want a strong trunk, you can let the ficus grow freely for two years at the beginning of the upbringing, because it will easily tolerate the radical design pruning that will be necessary afterward. Subsequent regular pruning is essential – otherwise, the little tree will quickly lose its shape again.
At the latest, when six to eight new leaves have appeared on a shoot, a new maintenance pruning should be carried out. Some species form inappropriately large leaves, but because the Ficus species also tolerate leaf pruning well, the leaf size can be easily adjusted. The happy-growing ficus regenerates well and also sprouts again from the old wood, but large cuts should be treated with wound closure paste.
Cut pine as a bonsai
Several species of pine (Pinus) are also suitable to be grown as bonsai. For their pruning, it is important to know whether the particular species sprouts with new needles once or twice a year: Species with two shoots per year are pruned down to a few needles in early to mid-summer on the newly emerged shoots (“candles” they are called). In addition, buds further up the shoot are cut at the top to provoke their outgrowth in the second sprout. Once the second budding has occurred and matured in the fall, superfluous shoots can be removed. This includes, for example, all but two, if a lot of shoots arise from a single point and necessarily vertically growing shoots. Finally, plucking out old needles can still slow down the growth somewhat.
For species with only one shoot per year, the newly formed candles are only slightly shortened in early or mid-summer, and in addition, already excess shoots can be selected. Especially vertically growing shoots should be removed. The old needles of these pines can also be plucked out in the fall to slow down the growth.
Pruning maple for bonsai
Maple bonsai (Acer), which often grows picturesquely, should be pruned judiciously. Although pruning of shoots and small branches is possible year-round, design pruning should definitely be done in the fall or summer to avoid heavy water leakage (“bleeding”) and still promote rapid overgrowth. Acer is susceptible to fungal diseases, so a wound closure product should be applied promptly whenever possible. Leaf pruning in summer is tolerated by the somewhat sensitive maple only every two years – or annually if only part of the leaves is removed. In this case, it is advisable to remove conspicuously large leaves or to selectively defoliate areas that are too vigorous in order to slow down their growth.
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