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Bonsai Watering Basics to Keep Your Tree Healthy

October 18, 2020Beginners, Care

Bonsai and watering can

Proper bonsai watering is a particularly important aspect of practicing the hobby. Let’s look at why a careful approach to watering is so vital, explore when and how to water, and cover a traditional and effective watering method.

Watering is one of the most essential and critical activities for the bonsai practitioner. Serious students studying the art under bonsai masters often spend years learning when to tell whether a plant needs water just by looking at the soil. 

For those of us caring for plants several steps removed from priceless, 500-year-old living works of art, the pressure isn’t quite as intense. However, the need to understand and observe good watering practices is crucial for keeping bonsai alive and healthy.

Because bonsai soil consists of coarse and mostly inorganic components, it dries out more quickly than other types of soil.  Bonsais’ compact root systems and the small pots that house them compound the need for frequent watering.  It’s probably safe to say that most bonsai owners have lost one or more plants by failing to water appropriately. 

Let’s examine the basic whens and hows of watering to help you keep your charges alive, healthy and hydrated.

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When to Water Bonsai

The ideal frequency with which you should water is influenced by climate, the season, current weather conditions, and your bonsai’s microclimate. Let’s take a closer look at these factors:


Bonsai hobbyists in more tropical locations, such as Florida, experience warmer temperatures throughout the year. However, frequent rainfall may mean they actually need to water less often than those in more temperate zones. Bonsai enthusiasts in hot, dry climates like the American Southwest may have to water multiple times a day for much of the year. 

Keep in mind that light, gentle rains may not be enough to keep your bonsai hydrated, especially in the summer. Dense foliage can act as an umbrella, shielding the compact pot from a light rain so that moisture doesn’t reach or penetrate the soil.  Never assume a short drizzle in the middle of a dry spell has provided adequate water for your bonsai collection. Check the hydration of your plants as often as necessary to ensure they don’t dry out.

Season & Weather:

Mother Nature plays a key role in the need to water, and bonsai hobbyists learn to pay close attention to time of year and weather. As caretaker of your bonsai plants, it’s your job to stay attuned to when and how often you need step in with the watering can.

In the Midwest U.S. where I live, for example, I water almost daily during the hot summer months When temperatures are consistently in the upper 80s and higher, I check the plants every day. Unless we’ve had a decent rain, most of the time they need water. Cooler temperatures and more frequent rain in spring and fall mean the plants don’t dry out as quickly. Therefore, I may only need to reach for the hose or can every few days.

After temperatures really drop at the beginning of winter, trees go dormant and need less water. I overwinter many of my hardy outdoor trees in a protected location that still leaves them open to moisture from rain and snow. Because they get precipitation, I seldom need to water them from December through late February.

I overwinter a few of my less hardy non-tropical deciduous trees in my unheated, attached garage. Since they are dormant and in a cold location, they don’t dry out quickly. However, they don’t get precipitation, so I water them thoroughly every couple weeks.  

My tropicals spend the winter months inside by a window. The low humidity of winter’s forced air heat dries plants out fairly quickly, so I water them every few days.


The composition of each bonsai’s soil, as well as its location in your yard (or – for certain species – inside your home) helps make up that plant’s microclimate. Think of microclimate as a way to address the individual needs of each plant when it comes to water, light, and soil mix.

For example, you might place a dwarf rhododendron bonsai in a partially shaded area, while a juniper resides in a spot with full sun all day long. Furthermore, you might choose to use different soil mixes for each tree. The juniper’s soil may have few or no organic components, while the dwarf rhododendron’s mix might contain some organic matter.

In this example, both trees might reside mere feet from each other. However, they have very different microclimates that affect their watering needs. The juniper would require more frequent watering than the rhododendron. It lives in a sunnier location and its soil retains less water. 

What Time of Day is Best for Watering Bonsai?

Is there a right and wrong time of day to water?  Not necessarily, although there are some things you may want to avoid doing routinely.  Some plant experts caution against watering in the heat of the day. They contend that sun shining on wet leaves acts like a magnifying glass and damages the foliage.  Others warn that watering at night sets the plant up for disease since the foliage stays wet long after sunset. 

Most bonsai hobbyists seem to gravitate to watering early in the morning or early in the evening. My recommendation is to choose whichever works best for you. Then make it part of your routine to water at that time each day.

Some experts recommend early evening watering as the most ideal time, and I tend to agree.  Watering at this time gives the foliage the opportunity to dry prior to nightfall. It also allows moisture to remain in the soil overnight, giving the tree plenty of time to rehydrate. Early evening advocates contend that morning watering is less efficient. They point out that soil dries out quicker in the heat of the day, providing less time for the tree to absorb the moisture it needs. 

How to Water Bonsai

You have two simple goals when watering bonsai:

  1. Water thoroughly but gently – get the water into the pot without displacing the loose bonsai soil. 
  2. Water to the saturation point – keep up the flow until you see water coming out of the bottom of the pot.

The traditional method of watering developed by Japanese bonsai masters is to use specialized watering cans with very fine roses at the spout.  The roses control the flow of the water, creating a fine gentle shower. I own a lovely metal Haws watering can equipped with a fine rose that I enjoy using with my bonsai. Haws even makes a cute, pint-sized version of their classic watering can. It’s perfect for giving small and indoor bonsai a needed drink.

Bonsai Watering With a Garden Hose

In modern times, many people prefer watering with a garden hose for speed and convenience. In the summer months when we leave the garden hose connected to the outdoor faucet, I generally use that to water my bonsai.

A standard hose sprayer delivers a strong spray capable of sending bonsai soil flying out of the pot, so you need something with less force if you plan to water with a hose. Special spray wands designed to water bonsai deliver a gentle fine spray that hydrates without displacing the soil. Wand attachments tuck easily under foliage so that the fine spray actually reaches the roots.

Alternatively, you could look for a regular spray head that adjusts to multiple spray patterns. You’ll need it to have a “gentle spray” setting that effectively waters the bonsai but doesn’t move the soil. Keep in mind that a gentle spray delivered from overhead might not make it through the tree’s canopy to hydrate the soil and roots below. So, if you go this route, you’ll need to take extra care to ensure water reaches the soil under the bonsai’s foliage.

The Immersion Method

A discussion of bonsai watering wouldn’t be complete without briefly touching on a third method. The immersion method has long been a traditional watering technique used with bonsai.

To use this method of watering, first place the potted bonsai into a container or stoppered sink. Next, fill the container with water up to just below the top level of the soil line. As the water rises, it soaks the soil from the bottom up, eventually moistening the surface of the soil. 

This technique is often used when transplanting and repotting bonsai, and less often as a routine watering method. Sometimes practitioners will use immersion to give plants a thorough soak in the summer months or to feed them with a soluble fertilizer.

Overwatering Bonsai

Is it possible to overwater bonsai? Yes. Even though bonsai soils are designed to be fast-draining, they can vary in the degree of organic matter they contain. Organic matter holds moisture and too-frequent watering can make the plant prone to root rot. 

The key is to be aware of the composition of your plant’s soil, and pay attention to weather, temperature, and hydration level. If the soil is moist, wait until it starts to dry out a bit before watering.

In Summary . . .

Compact root structure, unique soils and shallow pots make paying attention to watering a critical component in the practice of bonsai.  Practitioners will take into account their climate and season, the weather and the microclimate of each tree to determine how frequently to water. When watering a bonsai, do so gently and thoroughly, taking care not to displace the soil. Stop only after the water begins to drain from the bottom of the pot. 

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