Bonsai losing leaves
My bonsai loses leaves - What can I do ? A question to read frequently in every bonsai messages board. Almost every bonsai enthusiast has experienced leaf dropping at bonsai. Often - but not always - the reason lies in mistakes in bonsai care. With a little background knowledge leaf shedding loses its horror or can be avoided completely. In the following we have collected some points that can help you to understand and what is to do with your bonsai tree.
Bonsai, like all plants, need light - a lot of light. They gain energy from light through photosynthesis. At the same time they consume energy through their metabolism. The metabolism is particularly high at high temperatures.
A change of location changes the supply of light, especially in indoor bonsai. They come from bright greenhouses into a normal, clearly darker apartment. In autumn-winter the temperature in the flat is often even higher than in the greenhouse.
This poses a problem for the indoor bonsai: High energy consumption due to metabolism combined with low energy production due to insufficient light.
How does bonsai solve this problem ? Quite simple: By dropping the leaves inside the crown. They consume more energy than they can produce.
How can you help the Indoor bonsai ? Place your Indoor bonsai bright and cool, especially in the dark season. And bright means "as bright as possible", i.e. directly into the window.
If too little water is poured in midsummer, a bonsai plant can wilt after only a few hours on windy days outdoors. In many cases the leaves dry very quickly and fall off. Water the bonsai moderately in the next few weeks. If the tree is still alive, it will often recover again. With strong bonsai (e. g. Chinese elm) often very fast.
Diseases and pests
Strong foliage loss due to disease occurs much less frequently in bonsai trees than is often assumed. If you suspect an illness (such as Pine wilt) - ask a specialist. Good photos, samples of leaves or needles are very helpful for the analysis. Do not treat the bonsai until you know exactly what disease it has.
Leaf loss through over-fertilization can occur with excessive fertilisation with nutrient salts. Nutrient salts are very small molecules that surround themselves with a water envelope. If there are suddenly too many nutrient salt molecules in the soil, it can happen that the nutrient salt molecules extract the water from the root cells. The root cells "burn" - the root cells can die from this osmotic shock. Without intact roots, the tree suffers and may throw off more or less leaves. Since most bonsai enthusiasts fertilize with organic bonsai fertilizers, overfertilization with nutrient salts is rather rare.
Some pesticides lead to rapid leaf fall in certain tree species in certain situations. For example, bonsai of Japanese apricot do not tolerate the insecticide Perfekthion at all, Chinese elms react to Perfekthion regularly with leaf shedding when sprayed in the greenhouse. They don't show any problems outdoors. Both bonsai species recovered quickly after the leaf ejection.
Leaf loss after repotting
We sell 20-30 bonsai pots a day even in hot midsummer. What happens when customers receive the pots? In many cases it is use to repot a bonsai the same day. Does this make sense ? Definitely no. There is almost no reason to repot in midsummer. Experienced bonsai friends never repot in midsummer. This puts your bonsai under extreme stress and in almost all cases it reacts with partial or complete loss of leaves. Some very robust bonsai (e.g. Chinese elms, many maple bonsai, azalea bonsai) survive such a procedure. Others, especially conifers, die more or less quickly. Never repot in midsummer !
Complete leaf shedding in autumn
Is normal for most deciduous trees in temperate climates. Almost all outdoor bonsai lose their leaves in autumn. But also coniferous bonsai can naturally lose all leaves or needles in autumn. Typical examples: Primeval sequoia Bonsai (Metasequoia), larch (Larix), golden larch (Pseudolaris).
Partial leaf shedding in autumn
Is quite normal for many needle bonsai (for example pine - pinus). Needles of the past years are dropped. Whether this "partial dropping" is normal depends on the tree species. Many species of conifers discard needles after 2-3 years (for example Weymouth pine - Pinus strobus, Scots pine - Pinus sylvestris, Spruce - Picea), but some only much later. For example Black pines bonsai (Pinus nigra) lose their needles after 3-8 years.
What to do ?
Inform: Before they act - inform first. Call your dealer. Ask your questions in a bonsai messages board. Bonsai lovers are happy to help.
Brighter location: If an indoor bonsai looses leaves slowly but steadily shortly after delivery or in autumn-winter - keep it very light and cool.
Don't panic: For many bonsai autumnal leaf-dropping is normal. A good way to wire and shape it without the disturbing leaves. Even with an illness - don't panic. Strong trees don't die right away. 1-2 days to inform they always have.
Remove old needles: In the middle of September to the beginning of October you should remove the old, yellowed needles from needle bonsai. So they can find out if it is a normal autumn drop of leaves or if the tree has a real problem.
Do not hectically repot a bonsai: There is only one reason to repot quickly after a sudden leaf throw. Repot only if they have overfertilized their bonsai with a nutrient salt. Then an immediate change of the bonsai soil makes sense. In all other cases - do not repot hectically. First ask, inform, think in peace.
No excessive watering: If a bonsai throws off leaves, it needs less water for the next few weeks. It can evaporate much less water due to the missing leaves. Therefore - water a bonsai moderately after leaf dropping - ie. do not let it dry out but above all do not drown. The healthy middle is - as so often in life - the best recommendation.
First determine disease - then fight it: Many diseases can only be determined by experts. Do not treat a plant disease until you know what your bonsai has. A wrong treatment usually harms more than it benefits.
Do not hectically change location: Every change of location costs the bonsai energy. He has to adjust to the new location every time. Therefore: Better to consider 1-2 days, then decide on the best location and leave the bonsai there for a long time. A second change after a couple of days damages more than it uses.