I'm Thirsty And I Can't Get Up!

by Arthur Skolnik

"I bought this Jupiter in a mall two weeks ago. I didn't get any written instructions with the tree but I did what I was told and watered it once a week. I misted the foliage with water every day. I'm sure it has grown, but why are the needles crispy and brittle to the touch? What did I do wrong?"

If some of this sounds familiar, fear not, you are not alone. My answer, "Your first mistake was sociological... buying the tree in a mall. Your second mistake was sociological too, you followed the instructions."

Sadly, the likelihood of this tree having been purchased in a state of 'eternal dormancy' is quite high. I have seen dead Bonsai for sale and sensed they were dead even though the foliage wasn't crumbly yet. From the moment a Juniper dies to the point where the foliage crumbles like a potato chip when touched, may be anywhere from 2-4 weeks, depending on the conditions surrounding the tree. (Caveat emptor) The most obvious horticultural misdeed in this case - improper watering, not only by the owner, but the seller too. The single most important aspect to successful Bonsai growing is... proper watering. Learning to care for trees in pots is like learning a language. Each variety may have its own dialect, or nuances, but the basic common denominator is the same... listen to and sensitize yourself to, their thirsty cries for water. Aside from looking at them, watering your trees will be the aspect of care you will give them the most.

At issue here is what proper watering really means. When to water is one question and how to water is the other. Deciding when a tree is dry enough to be watered is at the first step. If the soil becomes dry to the bottom of the pot, some, if not all the roots will become damaged and tree could die. But the opposite is also true. If the soil stays moist all the time, the roots will begin to rot and the tree could die. This does not mean that Bonsai live within an ideal or narrow range of moisture conditions which necessitates the owner quite his day job or be retired to maintain these delicate conditions. True, a Bonsai grows in a shallow pot. Also true, roots can't reach out for water and they can't get it on their own. You have to be there to water when they are dry. They depend on you. Learning to tell when a Bonsai is dry is like learning a simple language. There are rules to follow which can be bent or adapted to each season and nuances to be sensitive to depending on the variety of tree, where it's growing, etc.

Most Bonsai soil recipes contain in part, and to one degree or another, organic matter such as humus, compost, leaf or bark mulch and other water retaining components such as Turface or Haydite. Research has shown that 50% of a good soil mix should be air! The other 50%, the growing medium or Bonsai soil, will absorb, hold onto, then give up water at rates that vary greatly depending on many factors. The depth of the pot, the type of tree, the season, (sun, wind, rain, snow) relative humidity, position of the tree in your yard and on the planet and whether or not there is ground cover such as moss on soil surface are all factors which influence the need for and frequency of watering.

So what is the rule? How do you tell if the soil is dry? Here's what I find works. When the soil surface is dry, it does not mean the tree needs water. It just means the surface is dry. This can happen 1 hour after the tree has been watered if it's sitting in full sun. When the surface is dry it's time to check if the soil beneath is dry enough to be watered. The 'dig test': dig a hole with your finger, half way down (the depth of the pot) into the soil, near the edge of the pot and excavate a little hole. The soil is dry enough to be watered if 3 observations are made.

#1... The soil tumbles back into the hole as you are digging the hole, like dry sand on a beach.

#2... If after you have removed your finger from the hole there is no soil stuck to your finger the soil is dry.

#3... If the colour of the soil at the bottom of the hole is the same as the colour on the surface the soil is dry enough to be watered. (If you don't want to spoil your new manicure, use a pencil to do the 'dig test'. This can be especially helpful with cascade pots).

Obviously, soil doesn't become dry in an instant. It's a slow process depending on many factors. If after you have done the 'dig test' you cannot decide if the soil is dry enough to be watered and it's spring or summer, it's best to water. It is very difficult to overwater a Bonsai if it is potted in proper Bonsai soil and the tree is outside in the summer. If in the summer you have been watering on a daily basis and you plan to be away for a few days, either make sure someone, or a foolproof automated system, is in place to water for you, or, pray for rain. Otherwise you may come home and find an expensive collection of beautifully shaped firewood, (kindling if you had mame). If, during a cool spell in autumn you can't tell whether the soil is dry enough to water, it's better not to water. As plant metabolism slows the need for water and the rate at which it is taken up and used, slows too. Use common sense. If you are going to be away from your trees for a few days in fall and they are not dry enough to be watered before you leave, water them anyway. This will take them through the period you will be away and soil which stays moist a little longer won't harm the trees. Not long after I first became involved with Bonsai growing I was amazed at how tuned to the weather reports on radio and TV, I became. Watering many trees can be very time consuming. Don't think of it as a bad thing. You can take advantage of this quiet time communing, developing a closer relationship with your trees if at the same time as watering, you inspect each one. Look for insect problems, the need for pruning, whether a tree needs to be turned toward or away from the sun, if suckers need to be removed from the base, if soil levels need to be topped up, if star moss or weeds have taken hold, etc. This is a quiet time. It's quality time too. Later in the day, when things are hectic at work, I think about and look forward to returning home and tending to the needs of my trees.

You know you have to water when...

Deciduous leaves drooped, tree looks pooped.

Needles of pine have lost their shine.

Flowers have wilted, water was jilted.

Boxwood looks wrinkled, if you've not sprinkled.

Juniper needles don't hurt, please water the dirt.

One of the important things I look for when I top-water is how quickly the water is absorbed into the soil and how quickly it finds it's way out the bottom of the pot. If the soil level is such that it is lower than the lip of the pot, there is a shallow space for water to pool, temporarily between the top of the soil and the upper edge of the pot. I want to see water being absorbed quickly in from the top and then rushing smoothly out from the hole(s) at the bottom of the pot. This tells me there is still plenty of room in the soil for roots to grow into. Water which is slow to be absorbed may be a sign that a tree is becoming pot bound.

As explained, the when to water is when the soil is dry. If you have a choice, it's best to water in the morning. Trees and plants will use readily available water during the day. At night the process of plant growth is reversed and roots do not benefit from being watered. In fact, excessive watering at night over extended periods of time, promotes the formation of fungi, mold and mildew.

Now for the how. The most effective way of saturating bonsai soil is by submerging the pot into a sink or other container of cool to luke-warm water so the water level rises to a point either just below the pot or just above the soil level. (Cold water temporarily slows root growth and hot water will poach roots). If you are using water from a garden hose which has been lying in the sun, let the water run until the hot water in the hose has been flushed out. Completely saturating the root mass and surrounding soil ensures thorough watering. It also fills the thousands (hundreds if it's mame) of tiny air spaces between soil particles and gives the porous material the time it needs to absorb all the water it can. This is important because after the soil immediately surrounding the root ball has begun to dry, the slightly more moist soil beyond it, relinquishes it's moist bounty. In other words, once the roots close to the trunk have taken the moisture that is available out of the soil the rootless soil beyond has more water to give.

If the Bonsai has been submerged to a point below the edge of the pot, water will wick upwards slowly through the hole(s) at the bottom of the pot. You can hasten the upward movement of water by gently splashing water on the surface of the dry soil. You'll know it's time to remove the tree from the container when the soil on the surface is drenched. Watering this way is clean, no soil floats away. But, it can take up to an hour until this is finished. A much quicker way of watering is by submerging the tree into a container of water so the water level rises to a point above the edge of the pot (and soil). Some soil may float away but the tree only needs a few minutes to drink. If the water level is above the soil level, you will see air bubbles rushing up from the soil with a sizzling sound as water is being absorbed by the soil. Once the bubbles have stopped, remove the tree from it's drink in the sink or unplug the sink.

In either case, it is not necessary to time how long the tree has been in the container for. Bonsai soil is like a sponge... it will absorb all it can and no more. Leaving a tree in a sink-full of water for 2-3 days won't kill it, provided this does not become a habit. Over watering (damage) does not occur by leaving the tree in the container of water too long. Over watering is not allowing the soil dry partially between watering.

On many occasions, I have put thirsty trees, usually mame or shohin into a sink full of water and the water level was above the top of the tree. (Noah, is that you again?) This is a great way to water the soil and wash the foliage at the same time as long as soil particles don't stick to the tree as it is being removed from the sink. Trees can stay under water for a day or two, once in a while, without any ill effects. I don't have any statistics on how long trees can remain underwater, be removed and still survive.

Another way to water and the most practical if you have many trees, is from the top with a hose and watering wand. Obviously, don't blast the soil away with water, ("Scotty set your phaser on stun"). To ensure the soil has had enough time to absorb all the water it can, water each tree several times! A good practice is to water the soil, trunk and foliage of one tree, go on to do another few, then come back and redo the first and second and so on, again.

Let's do an experiment. Fill a container with a measured amount of water, say 10 liters. Submerge a bonsai in the container. Remove the tree after the soil has become saturated and hold it over the container until the excess water stops dripping out. Now, measure the remaining water in the container. Say it's 7 liters. This does not mean that the next time the tree is dry, you have thoroughly watered the soil by pouring 3 liters of water over the soil. If you do, some or most of the water will work it's way to the bottom of the pot and out the hole (s) at the bottom. You will not have thoroughly saturated the soil. That's why it's best to water each tree several times if you are watering from the top.

In rural Shikoku Japan, the famous black and white pine growing region, trees are grown in a nutrient poor soil, hard pebbles. Organic 'cakes' of fertilizer are kept on the soil to feed them and during the growing season, women (mostly) perform the crucial task of watering, almost every day! Great care is taken in fall not to over water. Trees should not head into winter with dry soil, as roots slow their uptake of water yet the soil should not remain drenched either. The roots of white pine are especially prone to damage so, pots are tilted sideways on blocks of wood or stones, so excess water can drip more quickly out the holes at the bottom of the pot.

Let's do another experiment. On June 1st., 3 identically aged Trident maples, in the same sized shallow pot, growing in exactly the same soil, are all watered at 8 a.m. local time. One is in Los Angeles, California, where it's hot and dry. One in London, England grows where it's warm and humid and the third, in Lima, Peru is just going dormant for the winter. The first one may have to be watered again before the end of the day because of the heat and rate of evaporation. The second maple, in London, may not need to be watered that same day and might go for another day before needing to be watered again if the weather is humid and overcast. The maple in Lima, is hardly growing, if at all, in preparation for winter, and may not need to be watered for 2 weeks or so. In this case, the disparity between watering frequencies for the same sized tree and pot varies from twice a day to once in two weeks. That's a huge variance! It's important to realize that if the tree in Los Angeles was watered once every 2 weeks and the one in Lima was watered twice every day, both trees would die.

On to the next part to the experiment. You now have the same 3 Trident maples at your home. (You can't believe the paperwork needed to import those trees). One maple, in the front of the house, is sitting on a dark flagstone wall. It's in full blazing, summer sun and there is a constant breeze. The second is in the back yard near a pond, on a bench with other Bonsai, in the dappled shade given by some big old fir trees. The last one sits beside the house, under the overhanging roof, in full shade, (where, by the way, there is 80% less light for the tree to use). If you've got a modicum of common sense and you are only slightly versed in the language of plants, you should be able to realize which maple will dry the fastest. Even though it is summer and plants are growing a lot and transpiring (loosing moisture through their leaves) relatively large amounts of water, each tree should be treated as an individual with respect to their watering needs. Because the trees are in 3 distinctly different set of growing conditions, each tree will have it's own watering regime. If you do not want to become a slave to the watering needs of your trees, the best approach is to find one location for them all. (If you said the maple in the front of the house needs watering most often and the one on the side of the house needs water least often, you're right).

Do not water your trees following a schedule! Do not assume that if one needs water, they will all need water! Having said that, and realizing it is next to impossible to over water a tree (grown in proper Bonsai soil) in the summer during the height of the growing season in dry weather I water all my trees almost every day. But, before I do, I do the dig test on a few trees. Even if some are moist enough to go another half day without being watered, I water them all at the same time any ways. Why? I have many trees. I cannot and do not have the time to inspect each one, every morning, every day. If I had only a few trees it would be possible to keep track of which one was watered when. But I have learned and developed over the years, (as all experienced Bonsai growers have), to keep a rough, kind of general, sense of things. An inexplicable empathy with the soil and the trees. A bond. If I know they are dry in the morning and I don't have time to water, and I know I won't rain, I have to make sure they are watered before the end of the day. If they are dry and I water and it rains later, this is not a problem because the excess water will drip out the holes at the bottom of the pot. (That's why bonsai pots have feet.) If it drizzles and the soil was dry, I know the neighbors will think I'm nuts for watering my trees, but the drizzle may not have been enough water to saturate the soil.

Misting the foliage is a good practice if the air surrounding the tree is dry. In the summer there is plenty of humidity in the air where I live. Besides, I often water the trunk and branches at the same time as watering the soil so misting is a waste of time and water. In winter, if you grow tropicals, the air tends to be frightfully dry if you do not have a humidifier. 40% humidity is what you are looking for to be on the safe side. In dryer conditions the rate of desiccation can be faster than the roots are able to replace the lost moisture. If there is a net loss of water over time in these dry conditions, the tree ill suffer. Leaf loss means water sits longer in the pot. A weak tree is a prime candidate for bug problems. Misting before you go to work and again when you come home in the afternoon makes you feel good but in actuality benefits the tree very little. The rule of thumb when spraying the foliage is to spray the entire tree, top to bottom, the trunk and underside of leaves too, until water drips onto the soil. Leaves do not absorb water and misting the tree with the entire contents of a spray bottle would, in effect, be over watering the tree. If you've sprayed properly at 8 a.m. and the air in your home is dry, by 9 or 10 a.m. the moisture on the leaves has evaporated. The rest of the day, the tree is loosing moisture through it's leaves.

An excellent way of providing an inexpensive humid environment for your tree is to set the pot on a 'humidity tray'. This is nothing more than a shallow container filled with water and pebbles. The hole (s) at the bottom of the pot should not be sitting in water, so place 4 corks, stones, stacks of pennies, etc. under the legs of the pot to keep the holes out of the water. The pebbles in the humidity tray are not essential but because they increase the surface area of water by each getting covered with a thin layer of water there is more evaporation and humidity around the tree. During the day as the water evaporates, the moisture in the air will create a beneficial humid envelope surrounding the tree. Do not choose a tray which is the same size as the pot. There needs to be a substantial moat of water surrounding the tree for this to be of any benefit. So for example, if the pot is 10 inches wide, the humidity tray should be about 14 inches wide.

If you ever find some of your trees are so dry they have severely wilted or are soft to the touch, resist your instinct to save them by soaking them. When survivors of a ship wreck are found, if they are suffering exposure and dehydration they are not given all the water they want or need immediately. The wise rescuers resuscitate the weakened rescues slowly. Flooding them would otherwise overwhelm their already stressed bodies. Moisten the foliage and let the water fall onto the soil. Then lightly water the soil or quickly submerge then remove the pot from a container of water. One quarter to one half hour later the watering can be completed. A near death Bonsai stands a much better chance of making a full recovery if it is resuscitated this way and given some extra TLC for a week or so. (This means, little sun, no wind and no fertilizer until everything seems back to normal).

Have you ever wondered why plant leaves grow toward the sun? A tropism is an involuntary response of an organism to a stimuli, in this case, positive phototropism. Repotting or root pruning can be a stressful operation. Root pruning is best done when the root ball is slightly on the dry side. Obviously the freshly potted tree must be watered immediately after being repotted. If not the dry new soil around the pruned roots will wick any moisture water away and further stress the roots. Mr. Kimura doesn't touch the root ball with his bare hand when he root prunes. He says his temperature is not the same as the tree. Not touching the root ball while root pruning sounds like a very small detail but wouldn't you want to do everything you could to stack your odds in favor of the tree surviving after repotting? The next time your newly repotted tree needs water, wait a little longer, wait as long as you dare after you've done the dig test to water. Due to positive hydrotropism the roots will be involuntarily drawn ever so slightly outward searching for water and grow a little more than they would have had you watered right at the moment you felt you should. This can only be safely done if you can stay at home and wait the extra 1/2 - 1 hour. It's a delicate thing. When you can't stand the thought of your tree going another moment without water, do it. How long to wait depends again on many factors, not the least of which is you patience and discipline. It's not as frightening as it sounds except for the first time.

If you live in the drier regions of the world calcium and sodium built up in the ground water will cause the water to be 'hard'. Two effects of living with hard water are a white flaky build-up on the rim of your pots and you will probably have to adjust the pH (a measure of acidity or alkalinity) in the soil. Often this is simple to do but it's best to do it right and have your soil and water tested so you can rely on a consistent 'fix' for your soil. (A third effect of hard water is you can't dive or jump into it from very high??)

I keep my mames (trees and companions in pots less than 3") in shallow wooden boxes or plastic flats filled with sand. I don't mind if the legs sink into the sand, I'm not looking for aesthetics. I'm just looking for a simple way to provide some relief from the intense heat for my really little guys. As I mentioned, I have a lot of trees and in spring one of the things I tell my trees in their annual pre summer pep-talk is, although I love them all, I am too busy to provide special attention to one group or another. If they can not survive with the care I will give them, I am very sorry but now is the time to leave. None have ever lef! When I water my small pots, I make sure to water the sand well too. The resulting extra humidity slows the evaporation rate from the tiny pots and does the trick until the next time water is needed. Another solution would be to grow my trees under a lattice but I don't like the look of it all. A 40% shade lattice can provide a lot of protection from the sun while still allowing plenty of beneficial sunlight through.

Don't use a moisture meter. (The probe and tip are comprised of dissimilar metals which when inserted into soil generate an electrical current through voltaic electrolytic action which is related to the amount of water in the soil). Different locations of soil within the pot however may contain varying amounts of moisture. The sharp tip on those meters tends to dive right to the bottom of the pot and the area of soil it measures is so small, a more accurate reading of the moisture content can only be arrived at by averaging the results from several tests. The very best tool you can ever use for determining the moisture content in soil (or lack of it), is your finger, your eyes and your common sense.

Bonsai are amazing living creatures. You can't watch them grow, but a few hours after they've been watered, if you do the dig test again, you will notice how much water has been used by a tree. They are like little drinking machines, a life form so different than a dog or cat or any other living thing that if you give them the care they need, they repay you with a life time (your life time) of joy and a deep sense of accomplishment and pride. Really, if you add up all the minutes of care you give to a particular tree during the course of a year and you compare the effort to the payback, I think it's worth it.

An experienced Bonsai person can tell when a tree is dry by the weight of a tree or how the foliage feels. An expert knows by the way it looks. A master just knows. The reason a Bonsai apprentice in Japan spends a whole year just learning to water is, his teacher cannot put into words what his heart and hands know. He can only watch and guide the student in the direction of proper watering.