Water is one of the vital elements that plants need. If this element is missing, the plant has to draw it from its reserves, and this will exhaust it. In the same way' if a plant suffers from an excess of water, the substrate will subside, the roots will smother and rot, leading to the plant's death. It is therefore necessary to find the right balance.
At which frequency must I water my bonsai?
There is not an ideal frequency as this largely depends on the ambient warmth, the degree of air humidity, the size of the container (a very small container or a flat one will dry out quicker than a larger, deeper container). To get to know the needs of your bonsai, you can to start by weighing it when the substrate is dry. This will be your 'reference weight'. Water it abundantly (excess water will flow out, by the draining holes), then weigh it again. The difference in weight corresponds to the volume of water that you have given. Weigh it every two days, watch its foliage, and touch the substrate with your fingers. Only water it again when it gets close to its 'reference' weight'. You will then quickly learn to detect when your bonsai is thirsty and you will no longer the need to weigh it at all.
Which water can I use?
Tap water at ambient temperature is suitable for species which withstand hard water, but generally this water will be too limy for acid-loving plants (Japanese Maples, Camellias, Azaleas…). In this case prefer rain water or failing that, mineral water such as Volvic® for example.
Must I mist water on the foliage?
This practice has to be avoided. Indeed misting the foliage when the air is dry will create all of sudden a humid environment around the plant which will change its way of breathing, by opening its leaves' pores… but with a delay. This could lead to the opposite effect of the one wished, as the plant with its pores wide open will dehydrate quicker than if you had done nothing at all.
It is best to favour a humid atmosphere by placing all around your bonsai saucers filled with clay balls and water. Of course, you have to avoid any draught which would disturb this micro-environment.
Must I immerse my bonsai in water?
This watering method can be dangerous as it can lead to an excess of water which is detrimental to the roots, as well as compacting the substrate. Only soak the pot of your bonsai if you have forgotten to water it over a long period of time or if the substrate is clayish and highly compacted (and if this is the case, a repotting will be rapidly necessary).
A few tips: only water your bonsai if the substrate is dry and give a volume of water equivalent to the soil's volume, favouring soft water (rain water) and create a humid environment around it.
