12 min read

Background

Freshwater is becoming an increasingly rare resource globally. In the Western Cape of South Africa where I live never before have we experienced drought to the extent that we are now. At the time of writing this article, every citizen's total daily water allowance has been reduced to 50L per day. This must include what we use at home, work or at the shopping mall. No municipally supplied, potable water may be used for irrigation. It is at such times that we must be especially conscientious about how we use water on our bonsai and take whatever means possible to save this precious resource.

I thought it might be nice to share some of my water saving tips with you, but I would also welcome you to share your tips with me so I can include them in the list below. Lets just keep it bonsai orientated please, I am sure how many times you pee into the toilet before flushing is something everyone else wants to read about :) 

Tip #1

Double potting

I am not actually too sure if this is the correct term, but I do believe it fairly accurately describes what is to be done.

On my recent trip to Taiwan I noticed many of the bonsai trees, although in their own bonsai container, were positioned on top of another much larger container of some kind. This varied from a large cement pipe to a wooden box.

Double potting bonsai trees

Image caption: A Hackberry in Taiwan that has been "Double potted."

As you know, surviving in a small container is a pretty strenuous life for a tree. This is made all the more demanding when the ambient temperatures rise, humidity is low, moisture content in the little growing medium there is is reduced to almost nothing by the end of the day; and then on top of that we are adding nitrogen rich fertilizers in an attempt to stimulate the tree into growth, oh, and should it actually grow a twig we quickly snip it off as it is out of profile!

The idea behind double potting is to:

  1. Encourage rooting in the chosen "primary" bonsai pot
  2. but also to provide adequate growing space for additional roots in a larger container below
  3. which can better ensure the trees health in more demanding times (such as as the scenario I described above).

To double pot, simply take your tree in its current container and place it firmly on top of a another slightly larger container (of any material) and give it a bit of a wiggle to embed it properly. The growing medium in your second container should drain well, so it should be sifted if it is not a graded product, and it should retain some moisture. Fertilize only the container which your tree is in to encourage roots to grow in this more "hostile" environment. Fertilizer run-off will in any way enter the container below. 

"Double potting" is not the same as "Potting up." 

Potting up encourages fast growth and does provide additional rooting space but requires much more water and fertilizer to keep all the medium moist and achieve the required results. Also, by simply lifting the main container and snipping the roots (at any time) which have grown through the drainage holes into the container below you are good to go. With potting up, you will need to essentially repot the tree.

Hackberry shohin bonsai double potted

Image caption: The growth of this shohin sized Hackberry bonsai of mine would by now have stagnated completely in our rainless, hot summer. Since double potting it a couple weeks ago it has sprung back into life and is growing very healthily, plus the water which was wasted in an effort to wet it properly now drains into the container below filled with Professional mix.

Water saving benefit

Water runoff from the main bonsai pot will now empty into the container below and serve to support the tree. Previously this water would have simply dripped onto the ground benefiting nothing.

Tip #2

The Tub

This next tip is probably going to appeal most to bonsai growers who have smaller trees and smaller collections but depending on how desperate you are to save water this solution might start looking really attractive at some stage.

Its really a simple method of watering to put into place and you may not need to buy anything as you probably have what you need laying around the house.

You will need:

  • Any tub or vessel for that matter that will hold water and not leak. It should be deep enough so that when you put the bonsai with the deepest pot into it, the soil surface should be completely submerged.
  • A second tub, of any depth but it should be a little larger than your longest bonsai pot- optional.
  • A rigid grid or several strong rods or dowels of the same diameter which you can put onto the tub in order to rest your bonsai tree onto while it drips.
  • Liquid fertilizer - optional

I am sure you already know where I am going with this, but the idea is to fetch your bonsai trees, one by one and soak them in the vessel filled with water. You must ensure that the container is completely immersed. When you first dip the container a lot of air bubbles will come to the surface (plus perhaps some nice fat white grubs if you are using a growing medium rich in organic material). Wait until these bubbles stop coming to the surface and then slowly lift the tree in its container out of the water while trying not to wash off any of your growing medium by disturbing it too much.

The 2nd tub now comes into play. Before the time prepare it by laying your grid (I use an old braai grid, but you could buy a small piece of mesh from a metal shop also) over. Place your bonsai onto the grid and leave it there till it stops dripping. You could fetch another tree and it can be soaking while you wait. After you have watered all your trees you can simply empty this collected water back into the 1st tub.

Water saving bonsai

Image caption. Placing the drenched bonsai tree onto a grid will allow the water to drip into the bucket so it is not wasted.

If you can get some liquid fertilizer and add it to your liquid in the first tub then you will be feeding your trees at the same time. Every time you dip them you will be feeding them also. This may reduce the amount of time you can keep the water before having to replace it due to an unpleasant odour, but if so you can still throw this water onto your trees one last time using a watering can. Keep topping up the bucket with fresh water as needed.

Water saving benefit

When you water with a hose considerable water is needed to wet and then to saturate the growing medium. Much of this water then drains from the container and falls onto the ground below. By using a vessel and immersing the tree in it you can ensure that the growing medium is completely saturated with water and whatever run-off there is will be caught and can be re-used.

Tip #3

Shade

This suggestion is in my opinion not a long term solution and should be used only when you have to eg. the height of summer or during the hottest or driest time of the year. Various species of trees prefer different amounts of sunlight, for example the needs of a camellia compared to a pine would be rather different. If a camellia is placed in a position of too much sun the leaves may scorch and discolor and growth will be greatly stunted. Pines however require as much sun as you can give them or growth will be lanky.

When I think of shade I also think of temperature and not only of sunlight. Sometimes you will hear people refer to a certain temperature in the shade and in the sun. Temperature can have a dramatic effect on our trees but I think we often attribute it to excessive sunlight. There is however a difference and it does matter.

Ways you can provide shade:

  • Shade-cloth
  • A large garden tree
  • Positioning your tree in a position behind a larger bonsai so at a certain time of the day the smaller, shaded tree will receive less sun.
  • Create a lower shelf onto which you can place trees which require less sun (and you might even catch some of the water runoff from the trees above when you water)

Shade-cloth is commonly used by bonsai enthusiasts around the world. I don't wish to get into a debate about the percentage to use nor the colour of fabric, only to suggest that you don't use 80% as this although perfect as a windbreak, will reduce sunlight too much for most plants. I believe I have mostly used 40% in a green fabric. The precise percentage and colour you can get answers on from other growers in your area or the local co-op.

Shadecloth for bonsai

Image caption. When I constructed my bonsai area I made the roof in such a way that I could drop removable frames with stretched shadecloth in and remove them when they are not needed for maximum sun.

What I do want to place some emphasis on is that although it will take extra effort, try to create temporary shade-cloth solutions. The reason for this is that in summer the shade created is welcome however for the rest of the year it is unwanted. For example, if you have just defoliated a maple in late spring placing the tree in shade at first is advisable or the new, young leaves may burn in the sun. In winter when we in the western cape receive rain {hopefully!}if your trees are still under shadecloth, they will be standing in very wet conditions for much longer as the drying effect of the sun would be much less than without the shade-cloth covering. 

Shadecloth for bonsai

Image caption. This shade-cloth was stitched so that it could be fed onto stainless steel cables. This means it does not wave around in the wind and enables me to pull it back when I don't need the shade. The side tassels were made by cutting the fabric into thin strips which frightens birds but also helps reduce late afternoon sun which would otherwise slip below the horizontal fabric.

Garden trees do offer some relief for bonsai placed beneath them during the hottest times of the day. If you have such trees in your garden then utilizing them instead of shade-cloth is a free, ready-to-use solution although you of course have no way of knowing just how much sunlight you have reduced.

A small word of caution here is that if these trees are inhabited by squirrels, they may be inclined to steal your fertilizer or even bury nuts in your growing medium. Another potential problem, depending on the garden tree is that some of them may be infected or harboring pests which could drop down onto your trees, contaminating them also. Lastly, if it does rain the canopy of leaves will prevent most of it from reaching your trees, which means you might be left scurrying around in the rain moving your trees (although this is sure to provide some entertainment to family and neighbors).

Looking at your growing benches and identifying trees which need more shade, you can alter their position by placing them behind larger trees. Although it may help only a little for midday sun, it could help considerably more for afternoon sun, which in my opinion is what does the most damage.

Positioning

Image caption. By positioning trees next to or behind taller trees, you can help to shade the canopy or even perhaps more importantly, the roots and container.

With a little creativity you can easily erect a lower shelf onto which you can place some trees which will in turn be sheltered by those above them. Such a construction might be nothing more than a couple of bricks with a wooden board on top. Never place your trees directly on the ground where it is easier for slugs and snails to get at them, and for earthworms to burrow into your containers. If you have dogs I would suggest not to place your trees at a level they can reach, as they may "mark" them, steal your fertilizer or use them as a chew toy - or all three!

Temporary shelf

Image caption. A makeshift shelf in Master Kimura's garden of cement slabs atop cement supports provide additional shade to more sensitive chojubai (flowering quince)

Lastly, sometimes simply moving your trees from their current position into another will go a long way to solving the heat problem. Say you have your trees in a paved and walled courtyard or near a wall; the heat both reflected and absorbed by these surfaces, can easily increase the ambient temperature in this area by several degrees. Heat stress can really debilitate a bonsai tree so simply moving the tree further away from the wall (minimum 1m) which should preferably also not be white or if so placing a reed, bamboo or other screen against it will help tremendously. I am not at all a fan of stone as a ground cover in South Africa, despite its popularity in gardens. In my opinion it greatly reduces ambient humidity and absorbs a large amount of heat which it emits till late at night. Rather plant indigenous creepers, use a mulch of peach pips or bark, or simply bare ground - its still better than stone. I agree, stone can look extremely attractive especially when neatly raked but its a more appropriate covering in colder countries.

Groundcover

Image caption. Below some of my trees I have planted bushes. These bushes thrive off the water and fertilizer runoff from the bonsai positioned on small tables above them. They cool the entire area down and don't reflect sunlight and heat like stone does.

Water Saving Benefit

Positioning your trees in more shade and reducing the amount of heat they are exposed to will reduce the amount of water lost through the leaves and evaporated from the container. This will mean you might be able to stretch the intervals between watering to a day or even more. Be observant of too much shade which will lead to among other things; increased leaf size and longer internodes. However if its the difference between losing the tree and a temporary setback to your styling, the path to choose is really a no-brainer.

Tip #4

Tree Arrangement

Many people mistakenly think that all there is to watering is keeping the growing medium of their bonsai wet. In fact, correct watering may take many years to master as there are so many variables which influence the trees uptake of water. For instance, if the tree has just been repotted it does not have the capacity to absorb much water, or if it has just been defoliated it has no need for much water as no water is lost through the leaves. If you’re interested to know more about the “art of watering” then look at this previous article I wrote.

The logic

If you think of a tree like a Swamp Cypress living in an environment such as the Florida everglades in the USA which is perpetually wet. Then think of an Acacia which in nature can grow in rather arid environments. You cannot imagine these trees growing side by side in the wild now can you; yet we attempt to do just that in our bonsai collections. Trees which prefer certain climatic conditions are not necessarily compatible with those which prefer something rather different so try as best as you can to meet each trees preference.

I am not sure how you grouped your trees in your collection but perhaps you took one or more of these considerations into account:

  • Species: If you have more than one specimen of a species try to group them together. A Chinese maple and a Japanese maple for example are both Acer’s and although their preferences for water, temperature and humidity might be a little different its close enough for us.

Grouping bonsai trees

Image caption. Grouping similar species, as I did here with all these conifers, makes watering easier as the demands of the trees are very similar.

Size: Grouping trees of similar sizes makes a lot of sense as no tree will be sheltering another from sunlight and you are less likely to overlook watering one as you missed seeing it. However, trees in very small pots are likely to have very different water needs to tree’s potted into over-sized containers. 

Grouping by size

Image caption. When you group trees by size its of course easier to see all your trees, and see whether they need or do not need any water at that time.

Special needs: I used this term as here I am referring to trees which were recently collected, trees which are recovering from a disease or insect attack such as spider mite or root rot, trees which have been defoliated and such. Any of these examples, and there are others, may influence however temporarily it might be, the placement of the affected tree or trees.

Grouping by special needs

Image caption. The worst thing you can do to a flowering tree is to overhead water it. So set it aside and water only the soil, carefully, and the blooms will last much longer.

    Water saving benefit

    The benefit of grouping your trees in a manner which is more considered or logical than simply because there was an open spot on your bench, is that when you are walking through and watering your trees it is easier to make those snap decisions to water or not to water. In contrast, if all your trees are just thrown together you’ll most likely end up watering them all the same when in fact some won’t need any and some needing much more.

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