How To Keep Your Bonsai Tree Healthy
If you're reading this page, you’ve probably just become interested in the art of bonsai. Perhaps you've just acquired your first tree or you've recently received one as a gift.
This is a basic care guide to get you started and keep (or recover) your tree in a healthy and thriving condition. Scroll down or use the links to the right for this page.
Be sure and visit the “Bonsai Home Page” for an explanation of exactly what a bonsai tree is.
I begin with placement because if your tree is in the wrong location, no amount of care you give it will really matter in time.
For example keeping an outdoor bonsai indoors, is probably the number one killer of these little trees.
The placement/location will determine air humidity, soil moisture, lighting, climate temperature and most importantly the proper and always changing cycles of all these depending on seasons and time of day or night.
Before you even purchase a tree you need to find out its basic requirements. A quick google search of the species and variety will bring up it’s general care needs which should include:
USDA Hardy Zone:
Sun or Shade Exposure:
We’ll discuss “water” and “soil” in a bit but let's take a quick look at the other two.
THE HARDINESS ZONE is the location in the U.S.A where the tree will have the right climate conditions to thrive or grow hardily.
Find your location at the “USDA Hardiness Zone Map” link.
You can find the link at the top right of this page, just below the main picture. Click the map in your general location and it will bring up your area with a simple color coded design. See what
color you live in and find your color on the map key to the left. The color will have a number and a letter such as (8a) which will be your hardiness zone. To the left and right of your zone it will show the “extreme minimum annual temperature” in Fahrenheit and celsius degrees.
Almost all plants will have a USDA hardy rating which the tag that comes with your tree or a quick google search will give you. Knowing your zone as well as the trees zone will determine if the tree will live at your location.
Cold climate trees must be able to go dormant (hibernate) every year to rest for the upcoming growing season. Without this dormancy, the plant will eventually die.
Warm climate trees, likewise will die from the cold.
One more note on climate zones. USDA hardiness zones as well as temperature ranges on plant tags will assume that your tree will be planted in the ground protected by the earth. Bonsai trees are very exposed to the elements in their shallow pots and small amounts of soil.
I like to subtract two climate zones from my actual locations zone.
The lower number the climate zone the colder it gets.
Myself, being in Climate #8a consider it climate 7a.
With my assumed zone being 7a, If I have a bonsai tree cold hardy to zone 8a or 7b , I consider it in danger without special care.
Trees cold hardy down to Zone 8a (my actual zone) should be kept in a cold frame to protect the delicate twigs as well as the roots from die back.
Trees cold hardy down to Zone 7b (one zone colder than my actual) I would mulch into the ground in their pots or just protect them from Northern exposure.
Zone 7a trees (my new assumed zone - two zones colder than my actual) I will assume are plenty hardy to handle the climate on their own even in a bonsai pot.
Zone 9a trees I will not bother with trying to keep at all unless they are tropical trees which can be kept indoors during the winter months
SUN/SHADE LIGHT REQUIREMENTS are quite obvious, just find it a nice home with the light requirements the tree likes. There are a couple of exceptions though.
First, as with the cold the shallow pot of a bonsai tree exposes it to more extreeme conditions. Be sure to protect it from the extreeme heat of the mid day sun. Second, is live tree mail order.
MAIL ORDER Purchasing a tree through the mail or online is a great way to get new material from a trusted seller and has become common practice today. You have to keep in mind though that the tree will be in a bit of shock.
Not only did it spend a few days bouncing around in a dark box, it likely came from a whole different climate than yours. Sure you may have the exact hardiness zone as the sender's location but they may have 75% cloudy days while you have 75% sunny days. Its also
likely the tree came from a greenhouse where the grower keeps it safe until it ships to its new owner. None of this is detrimental as long as you take a few precautions.
Mail order trees should at first be kept in a protected, full shade location regardless of it’s “full sun” requirements. Then slowly, over a couple of weeks, acclimated to its required light needs.
Watering Bonsai Trees
For maximizing the bloom time of a flowering bonsai tree, move them to the shade while they bloom and keep the flowers from getting wet by the rain or watering.
Although a lack of fertilizer, crowded roots and poor placement will cause a plant to become feeble and perhaps even die over a period of time, watering is the most important factor in keeping a bonsai healthy.
Allowing a bonsai to dry out completely can cause irreversible damage and will almost always kill the tree. However, too much water is probably the second biggest killer.
Over watering a bonsai tree will water log the roots causing root rot or deplete the oxygen levels in the soil and suffocate them. However, bonsai soil is made up of coarse materials to help prevent this and so should be watered more often than most potting soil. The trick is to closely monitor your tree and keep the soil moist and not wet or soggy.
After you become familiar with the particular tree and its soil, watering will become a simple and enjoyable practice.
In the winter months you won’t need to water nearly as much but it should still be monitored and not forgotten. The best way to keep a bonsai from becoming too dry or too wet is simply, careful observation, proper placement and the correct soil.
Mist spraying the entire plant regularly is beneficial and if brought indoors for a short time during the growing season, necessary.
WATERING MAME bonsai can be a bit trickier.
Tiny mame bonsai require close supervision and an acute awareness of weather changes.
A humidity tray can make this much easier.
Fill the tray up deep enough for water to absorb through the bottom hole of your mame pots and set them in. The idea is to let the little pots absorb enough water to become moist and then the tray water evaporate before they become too wet. Once the pots begin to dry, re-water the tray. It's a sort of mini hydroponic set up that works well once you get the hang of it.
Best Bonsai Soil
Bonsai, being in a tiny confined space, needs special soil to keep your tree healthy and thriving.
Contrary to what many believe, bonsai are not little tortured trees stuffed into a small pot to stunt their growth. The object of the game is to keep your tree as healthy as possible so it can be continuously improving and look it’s best during the process.
If you ask 10 different bonsai enthusiasts what's the best soil, you’ll likely get 10 different answers.
So if you're a beginner and getting different answers from everyone you ask, now what?
I think I can help.
The simple fact of the matter is some soils don’t work and some do.
The ones that don’t will kill your tree or at best, weaken it making it susceptible to the development of secondary problems. Which can also kill your tree.
Most all soils have too much organic material which clogs the pot and prevents proper health.
A bonsai soil that does work will have to meet some basic requirements. If you meet these requirements in your soil, your tree will live.
The complex truth and the controversy comes from the fact that there are many soil elements out there that can be used and some will work better than others.
Some may also work better in some locations depending on humidity, temperature and length of dormancy.
This is usually related to the drainage and rate of dehydration of the particular soil elements.
For the most part this can be effectively controlled by the size of granules and their ability to absorb and hold water. The more rain or cold your climate gets, the larger more free draining granules you’ll want to use.
The goal is to find soil mix ingredients with certain qualities either independently or in a combination of several mixed together to provide the ideal conditions.
What you use will vary depending on what's available in your area.
Proper Bonsai Soil Mix
There are several critical requirements for perfect bonsai soil
(1) WATER RETENTION, DRAINAGE & OXYGEN
Bonsai soil needs the ability to allow the water through but also retain moisture. If the water does not drain through, the roots will become weak from a lack of oxygen which can cause disease or root rot. If the water isn't absorbed and moisture held, you will be watering more frequently than is practical and washing out valuable nutrients critical to the health of your tree. Porous or absorbent materials are the trick. Lava rock, pumice, bark, and clay all have absorbent pores and can be found and screened into granular sizes and densities to allow proper drainage.
(2) NUTRIENT CAPACITY
The ability of the soil to hold nutrients without them being washed from pot with regular waterings. Clay is the ideal material for the purpose as it holds the nutrients in a form available and useable to plants without leaching with watering.
(3) BREAKDOWN OR LONGEVITY
Not the nervous kind but that's what you should be if your soil is doing this. If soil elements break down in the pot, the fine particles will clog drainage making your tree susceptible to root rot and disease as well as prevent proper oxygen flow in the soil.
The pH of your trees soil are important to the trees ability to absorb nutrients. Most plant will have basic soil requirements which is right around 6.5 with 7 being neutral. Some plants such as azaleas, rhodies and blueberries require acidic soil or a lower pH. of around 5.5 Still others will live in a wide range such as the chamaecyparis which can handle pH 5.0 to pH 8.0 and others like the cryptomeria will live in pH neutral (7) soil but will benefit from a bit of acidity.
Do a google search for your particular trees pH requirements and adjust the soil elements according to its needs.
Douglas fir bark pH 4.2
Pine or softwood bark pH 4.0 to 5.0
Diatomaceous earth pH 7.5 to 8.0
Pumice is mostly pH neutral (7) but it can vary.
Lava rock varies depending on the location it was mined from.
Making Bonsai Soil
Bonsai soil is created by sifting and mixing different materials together depending on the particular trees needs.
Here are some excellent soil elements that have all of the necessary qualities of superior bonsai soil. They can (except bark) be used alone or (including bark) be mixed to create your own recipe.
Don't forget to fertilize as these are all free (except bark) of organic components to avoid break down and clogging the soil. Bark sifted to remove fines will break down slowly enough to benefit your tree without causing problems by the time you repot.
Once you've collected all of your soil elements you will need to screen or sift them with a bonsai sieve to remove dust and fines as well as separate granule sizes.
Different sizes can be used depending on your climate and the size of the bonsai.
Smaller granules will dehydrate slower for small size bonsai and dry locations while larger will of course do the opposite.
1/8" is the smallest size you would want to use and all the way up to 3/4" would be suitable for large pots.
Pumice: A volcanic rock available in many sizes. Pumice has excellent absorption and retention capabilities. Rinse the dust out and sift the fines if present.
Pumice is mostly pH neutral (7) but it can vary.
Diatomite: Known as diatomaceous earth, turface or fired clay has all of the elements of an excellent bonsai soil. Kitty litter or oil absorbent are the most inexpensive and readily available source. Be sure it is made of diatomaceous earth and free of perfumes and dies. It needs to be sifted to remove the fines and dust to prevent clumping and turning to mush. It warns you when it’s drying out by turning white, it looks great when it’s damp, it has pest fighting capabilities and insulating value which perhaps could even help protect the shallow roots of your favorite bonsai tee. Datomite is usualy alkaline or low acid, so it is not ideal for acid soil loving trees by itself.
Diatomaceous earth pH 7.5 to 8.0
I use scent free “Special Kitty” cat litter with great success. I have seen people on forums and websites say it mushes. They are either using one with added scents (bad idea) or they are not sifting out the dust and fines. It is inexpensive and sold at WallyWorld. I have had this kitty litter in a moving stream vegetation koi fish filter for over five years as I am writing this and there is zero break down.
I have used it as a bonsai soil both as a part of a mix and by itself for over 5 years without any problems and with great success. It is pure diatomaceous high fired clay. The exact same thing as the much more expensive oil absorbent from Napa which people seem to love.
Crushed Lava Rock:
Like pumice lava rock can be sifted into different sizes to match the size of your tree. Prevent clogging your pot by rinsing it clean before use to get the dust out of the pores and prevent clogging.
Lava rock pH varies depending on the location it was mined from.
For trees that like some organics or an acidic soil such as pines, rhodies and junipers, bark is the answer. Bagged bark is available in fine or small sizes. Sift out the dust and then use different screen sizes to get varying sizes. It takes some work to get the desired small sizes and some bagged products will produce better results than others so it requires some trial and error.
Douglas fir bark pH 4.2
Pine or softwood bark pH 4.0 to 5.0
For trees that require a humus rich soil, many people use peat moss, peat humus or compost to fill the position. Humus is actually the result of the decomposition of these elements. Once dried out these materials are difficult to re-wet and they are a much finer particle size than is ideal which will reduce airflow and drainage.
Having said that, humus is sometimes a critical part of a soil mix for some bonsai trees like blueberries. And still others such as rhodies and azaleas will live and grow much healthier with it in their soil.
I was pretty stumped on how to get a humus rich soil without clogging my pots. I was using bark mixed with peat moss and spending a lot of time watering and frequently transplanting.
So I finally came up with the perfect solution. See what my favorite bonsai master does. Genius huh.
Well not so much me, but I think Graham Potter is. A quick search and I found an excellent article on soil and all of it’s scientific intricacies along with a simple solution that only someone with his horticultural knowledge could provide.
The answer is simply to use a quality liquid organic fertilizer. This will in fact provide the necessary nutrients of humus without the associated problems which organic solids will cause if added to your soil mix.
Or if you prefer the guaranteed analysis and ease of use of chemical fertilizers you can safely add “Humic Acid” to your bonsai soil with and in addition to regular fertilizers.
INDOORS OR OUT? Unless a bonsai tree is tropical or subtropical it must be kept outdoors at all times. An outdoor bonsai tree will die if it is kept indoors. It can not get the proper humidity, day/night temperature fluctuations or changing light requirements to stay healthy indoors. Although a healthy tree can be brought in a couple of days at a time during the growing season for special occasions, they should never be brought in during the winter. The tree must have a dormant season, a time of rest or hibernation which would be disturbed if exposed to an interior climate.
Fertilizing Bonsai Trees
Fertilizer is essential in growing and keeping your bonsai tree in excellent health and imune to the many problems that can arise. The small amount of bonsai soil is quickly depleted and needs to be replenished regularly during the growing season. It is especially important in inorganic soils as they do not carry all of the necessary nutrients like some organic soils may.
Either use a quality liquid organic fertilizer or Look for a liquid fertilizer or time release granules with equal parts (or close to it) analysis of:
N-P-K (#-#-#) found on the label of all fertilizer products.
N- Nitrogen: For leaves
P- Phosphorus: For roots flowers & fruit
K- Potassium: For general health and immunity.
Using an equal analysis fertilizer (or close to it) will provide an all around well balanced growth and health for your tree. Apply as by the directions from spring until late fall. Use from 7-7-7 to 15-15-15 during the growing season or 20-20-20 in the spring.