Sorting a water schedule will greatly benefit your bonsai trees growth, and once you are in a routine it will become a lot easier to remember to do and your tree will thank you for it. The first important step to watering your bonsai is to check the dampness of the soil to discover if your tree actually needs a drink.
A bonsai tree can suffer if it goes without water for a short period of time especially in peak summer, with bonsai roots unable to access the ground’s moisture and especially if you have an indoor bonsai forgetting to water your tree on time could cause the soil to completely dry out.
Interestingly though, bonsai’s are more commonly drowned by excessive watering rather than suffering from drought. This is because if there is too much stagnant water it will starve the roots of oxygen which will cause them to die and rot. So caution must always be taken before watering.
One of the best bonsai tree care tips is the chopstick test method to check the dampness of the soil which sometimes can be visually deceiving. If you have repotted your bonsai tree and used your own soil mix, deciding whether your tree needs watering can be easier as a looser soil can be scratched back, but if your soil has become quite compacted or if you are still not 100% certain that the deeper roots require watering or not, certainly use this method to help.
The Chopstick test
Take a softwood chopstick eg: a kebab stick and push it straight into the soil, careful to avoid any roots, to the bottom of the pot. Often the corners of the pot are best. Leave this for 20 minutes to allow it soak up any moisture (if there is any), then remove to check by gently feeling the buried end. If the stick is moist then no watering is needed, if quite dry then it will require watering and if the chopstick feels bone dry then it will require instant watering using the immersion technique (see below).
Keep utilizing the chopstick test to help develop a watering bonsai schedule and to make sure you hydrate your tree when it actually needs it. The regularity will obviously change throughout the various seasons as the bonsai pots and branches heat up or cool down.
Type of Water?
Generally speaking water that is fit for humans is fine for a bonsai tree. But rainwater is best for all plants, but cannot be always accessible. Tapwater is fine however it is good practice to attempt to evaporate as much chlorine as possible by allowing tapwater to stand in an open container for a few hours. You should always try and use water that is at room temperature so as to not shock the roots when they become hydrated, but if it is an especially hot day your tree will enjoy water that is a few degrees cooler to refresh the roots.
How to Water
The best method for watering bonsai is to using a fine rose head on a watering can otherwise it will not be easy to soak your soil evenly. Gently does it, water until it begins to flow out of the drainage holes then pause and wait for a minute. Repeat the process until the pot feels noticeably heavier. Take care to water the whole soil surface especially the area behind the trunk which is often neglected. If the soil is not taking the water and failing to absorb then change to the immersion technique (see below).
Misting your bonsai tree is an especially good idea if your specimen is kept indoors, this will help combat the dry inside conditions. Spraying the underside of the leaves as well as their tops with a hand spray bottle will help refresh the leaf and provide some much needed moisture.
Immersing your bonsai tree is generally an emergency technique when your soil has dried out so it fails to absorb any water or if your bonsai is in a clay-based soil that has become compacted. To follow out the immersion technique, place your pot slowly into a bowl of room temperature water (see diagram below) until the soil is covered by the water. Air bubbles will then rise from the soil, leave until the air bubbles stop which means the soil is wet through (this can be up to 30 minutes). When lifting the pot from the water it should feel noticeably heavier otherwise it means that it is not damp throughout the soil.
This should not be a regular technique otherwise clay-based soils will become even more compact and gradually solidify, repotting your bonsai tree is then a necessary procedure to ensure you correctly care for your bonsai.
Automatic Bonsai Watering Methods
If you are heading away on holiday then an automatic watering bonsai system may be a necessity for you to maintain your tree’s hydration, however there are plenty of factors to consider before relying on such a system. Continuous drip systems in theory are a good idea but they do not factor in the weather (if your bonsai is outdoors) and also the reservoir has the potential to run out if not calculated correctly. Soil sensors are a useful solution and potentially the most reliable but also a capillary type system such as the Hydrospike (pictured right) which keeps your bonsai tree soil moist and prevents over-watering or under-watering. It works by an automatic capillary action, drawing water from a nearby container when the surrounding soil dries. The Spike replenishes the moisture at the same rate your plant draws it from the soil.
Regardless of the method you choose, be sure to test it out for at least a month to check the efficiency of the automatic system you have decided to use.