Water 3 ways

Lets talk about something that all bonsai trees, or any life for that matter, cannot live without. Water. In all plants, water is not only a conveyor of nutrients, it is also a cooling liquid that helps the plant to resist wilting in hot summer days. Without water, nothing lives. But not all water is “built” the same. In this article we will be analyzing how water can take on different characteristics and what your bonsai likes best.

When you water your trees, have you ever wondered whats in the water? Well… it all depends on your source. Some source their water from an underground well or, municipal or “city” water or even, rainwater. Let me first say something very important, all of these sources of water are suitable to grow bonsai, however, we must analyze what is in our water to truly understand what our trees need. Let me explain. Some sources of water contain a high amount of minerals or high chemical content that may hinder the trees growth.

Municiple “City” water

For many of us, the only source of water is “City” water, and indeed it’s a great source. In most cities the water is filtered, and treated, and pumped out to us, but not all city water is the same. Why? The city has to source their water from somewhere. Some cities source their water from rain fed lakes, river fed lakes, springs, wetland preserves, deep wells, or even the ocean! Yes the ocean! In each case, the city determines what are its standard levels for minerals and additives. City water also is regularly monitored and as a precaution treated with chlorine. Here again the city determines how much chlorine and for how long the additional chlorine will be running through the pipes. Here in south east Florida, city water is not great. Our municipal water is sourced from a wetland preserve which has a high mineral content and is constantly treated with additional chlorine. Most city water contains heavy metals such as lead and copper, with additives of fluorite. Due to that each city dictates its own standards of mineral and metal content, the only way to really know whats in your water is to consult with your city water department. In the U.S., by law, each municipal water department must publish its levels each year.

What are the effects of city water on your trees? For the most part, city water is perfectly fine for bonsai trees. In my experience however, city water can have drawbacks. Some cities will switch water sources which means there might be a change in mineral and heavy metal content. City water can contain calcium, which with time builds up in the pots. Calcium can stain a pot and if you have ever had an antique pot you know how big of a pain it is to remove calcium build-up without removing the patina. Also if where you live is particularly hot, you can be paying quite a lot for water due to needing to water your trees multiple times a day.

Well water

Well water is another source of water which can also be suitable for watering your trees. Lets examine well water. Well water mineral and metal content is totally unique to where the well is drawing up its water. Why? Well water mineral and metal content depend on the soil type where the well was dug in. Well water is produced by rainfall filtered through top soil, sand, and rocks. However, mineral content and metal content completely depends of the soil content and how deep the well is. In many cases, shallow (10 to 12 feet in some cases), wells will contain sulfur, and iron giving it that rotten egg smell. This usually means that the soil contains these elements and the water needs more natural filtering to remove these. Wells dug between 15 and 25 feet will usually contain a high level of iron, giving the water the property to stain everything in a red film which can be difficult to remove. Deeper wells 30 to 100 feet can really be nice water. At this point the water has been completely filtered and free from most harmful or toxic minerals. In most cases at these depths a well can be accessing an aquifer. Let me translate. Sulfur can accumulate in pots and can become toxic for trees and stain pots. Too much iron in the water will stain the trees leaves which can block the suns rays and interrupt the trees abilities to make food through photosynthesis and it also will stain pots, accumulate and clog roots. Well water can contain high levels of calcium which can also accumulate and stain pots and clog roots. Well water is notoriously hard meaning that it has a high amount of dissolved minerals such as calcium and magnesium. Because well water usually contains a high dissolved mineral content, plants in general will have a harder time trying to absorb the minerals therefore building up in the soil. It has been my experience that when a tree has been watered with well water, the “bonsai soil” mix (which is inorganic, or in other words, soil-less mix) ends up being mucky with organic material. This hinders the growth of roots.


Ah rainwater,… rainwater is special. Rainwater has very special properties and the harder it thunders, the better the rainwater. Have you ever seen your trees react with greener leaves and an overall healthier look the day after it rained?  Its like someone gave it a shot in the proverbial arm. Why does this happen? Rainwater is soft water. This means that it does not contain high dissolved minerals. It contains nitrates which is the most bio-available form of nitrogen and is also slightly acidic naturally. During thunderstorms, the lightning helps provide electrically charged ions. All of these things combine into a clean source of water that your tree loves. Rain water is the most effective and cleanest way to water your trees. The best way to store rain water is in rain barrels or a basin.

To answer one popular question…

Some people, including some of my students, have come up to me and asked me about a zero waste water system, meaning recycling the water used to water the trees. Don’t get me wrong, I am all for a zero waste water solution. However, recycling this water is not a good idea. Why? Bonsai require the use of fertilizers, pesticides, and on occasion fungicides. Even if you use natural organic pesticides, fungicides, and fertilizers and even if its filtered, reusing this water will eventually kill the trees. If one tree gets sick, all the trees will get sick. Some will also use waste water to water plants, but a word of warning needs to be said. Human waste contains many yucky things. Medications like antibiotics , heavy metals, bacteria, high levels of nitrites, acidic ph, and so much more. All of these things will kill your trees in a very quick way.

The last word on water

Our trees are a source of pride. They are delicate because sudden changes can have a profound effect on them. All of these water sources can generally be adequate; however, the purpose of this article is to find the best source of water for our trees. Even though it may not be easy to get or store, rain water is hard to beat. Its free, contains all the right stuff and bonsai love it. So if it is possible for you to store rain water, it is truly well worthwhile.

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