Notes on Bonsai Care: the horticulture. 1.

Collated by Tony Moore, Blackmore Vale Bonsai Group. April 2019

Introduction

There are several aspects of bonsai care to get to know. Here we will focus on some of the what, how, when, why and sometimes, who, of how to get your tree into and maintain it in, the very best condition. Only then can a tree be worked into a particular design, over a period of years. But this is an organic art, literally! By keeping a tree in a healthy condition, you will keep it growing, sometimes to the detriment of your intended design for it. The only way to get the most from your trees is by learning to adapt to nature. Noting what can be seen in forests or parks can help here.

Human intervention begins when we interfere with nature and remove or grow a plant of any sort from its natural habitat and encase its roots in plastic or clay pots. To help the plant to thrive, we need to try to replicate its natural habitat as closely as possible.

The processes contained in any plant which help it grow and thrive are complex, but once grasped, there is much one can do to assist its healthy development: Its hormones and its food production and distribution systems. Also the soil it stands in and its reaction to environmental changes – climate, day- length, aspect, etc, all play a part.

Placing the container in the best spot for that species, in that condition; regular, timely watering and timely, species-specific feeding, the most appropriate compost mix, and the best drainage, is the best we can do to compensate for domesticating ‘wildlife’ for our own purposes.

It’s always important to remember that, like humans, plant species are all different, therefore “one size (of treatment) doesn’t fit all”. We must establish the needs of each plant then supply them, to get the best out of them, be that attractive flowers and leaves; a good crop of fresh food or an attractive ornamental plant like a bonsai.

Constrained in such a small amount of soil, all of a bonsai tree’s processes are concentrated, therefore magnified and all within your control.

Part 1. Watering

Us humans are always being reminded to drink more liquids in order to hydrate our bodies for good health. We cannot survive more than a few days without water.

Plants in pots are similar, with the disadvantage that they cannot choose when to drink!

Plants in pots, including bonsai, will suffer severe damage if their roots are allowed to dry out for more than 24 hours. On the other hand, over-watering will fill all the tiny gaps in the soil needed for Oxygen – a vital element for growth. Over-saturating the soil will also cause the plant’s feeder roots to rot, often with fatal consequences. A well-drained compost is vital. We’ve all learned the hard way when we’ve lost a plant or bonsai from these two common mistakes.

Summary note 1.The water we use is important, that is, the pH level of the water. pH is the “potential of Hydrogen” of the water and is measured on a logarithmic scale ranging from 1 to 14, where 1 is very, very acid and 14 is very, very alkaline. Each point on the scale equates to 10 times the previous number. On the scale, 7 is the neutral point, and is the point at which the majority of plant life survives and grows, but not all. Some plants, like Fuchsias, prefer a pH of 7.5. Others, like Azaleas, prefer 6 to 6.5. The trees preferring a lower pH are generally referred to as ‘ericaceous’ ( after Heathers – Erica). See appendix 1 for the pH scale. This chart shows how the pH of soil, either makes

each nutrient available to plant roots, or conversely, holds it in a form preventing its use by plant roots.

The two sources of water available to most people are domestic tap-water and rain-water. 2.

Tap-water is intended for consumption by humans, so has added chemicals, particularly Chlorine, and any amount of Calcium, dependent on your location. This makes it tend to alkaline, (pH 7+). White deposits gather on the soil surface and the pot, although this can be removed by gentle brushing with a toothbrush, or for stubborn stains, careful use of a weak solution of vinegar.

Rainwater tends to acid, (less than pH 7) depending on how it’s been collected. The rule of thumb is to use rain-water on all bonsai, as Chlorine in particular will halt some of the processes in the trees and restrict the fungus (mycelium) in the soil vital for take-up of nutrients.

However, tap-water is better than no water. Tap-water has its uses though, particularly for growing seeds. The Chlorine acts as a fungicide, preventing the fungus known as ‘damping off’.

If the only water available is from your domestic supply, fill a bucket or watering-can and let it stand for about an hour, allowing the Chlorine to evaporate. The water companies add Chlorine as a gas.

Never use artificially softened water, as the Sodium used in the softening process will damage your trees.

See appendix 2 for an (incomplete) list of trees and their pH preferences.

There are five methods in popular use for watering bonsai: i) A watering-can with a fine rose, for overhead watering; Watering cans and their rose

should be thoroughly cleaned regularly during their season of use, to remove any impurities which will have gathered there. The rose needs its holes clearing, or won’t sprinkle efficiently. Avoid watering the foliage. Water directly onto the soil.

ii) A hose with a wand attached, that has a fine rose; keep water off leaves, and needles of Pines. Keep the rose in the wand clean, and avoid leaving the hose rolled out in the hot sun, or the water will heat up. Be sure to empty the hot water away, before watering your bonsai, or you’ll boil your trees’ roots and leaves. These are living creatures you know!

iii) Immersion in a bowl of water; needed if a tree show signs in summer, of not having enough water. Sometimes soil becomes compacted under the trunk, preventing the roots in that immediate vicinity from accessing water. Also during overhead watering when the water first runs to the outside of the soil ball, leaving the centre dry. This problem can be apparent when buying a tree from someone, after repotting season (generally spring), and you need to wait for next spring before you can safely repot. Half fill a bowl with suitable water and immerse the bonsai in its pot in the water, covering the soil, until the bubbles stop. This will ensure that water reaches the root area immediately beneath the trunk. Remove from the bowl and allow to drain. If the air temperature is high, ensure that you don’t send the tree into shock by dunking it in freezing water! Trees have feelings.

iv) Automatic watering systems; these must be carefully managed, as not all species need the same amount of water. Best used when your trees are grouped in species. Regularly inspect each tree or risk drowning them. Bear in mind the ‘hot water’ effect in ii) above. Auto systems can work well temporarily, perhaps for a short holiday, once carefully set up and tested, but it’s recommended that bonsai enthusiasts team up with another, possibly local, bonsai enthusiast, who understands how to water bonsai, to cover each others’ watering duties at holiday time. (Bonsai nurseries use auto systems as a matter of convenience)

v) Misting sprays, come into their own in warm weather, when some species will not thrive without misting. Misting also deters spider-mite, which dislike dampness.

3. However, misting Pines is not advised. Learning which trees need misting and when, is another skill to be mastered.

Summary note 2.Not all trees require the same amount of water, so it will be important to learn the skill of ‘hefting’ or lifting the pot to determine how much water is still left in the soil. Bonsai students in Japan are trained over a 3 to 5 year period to achieve this skill, so keep practicing!The amount and pH of water each tree needs will be determined by its species, it’s age, its condition, the amount of drainage holes in the pot, the composition of its compost and its aspect (the direction it faces and any shade it has). As you can see, it’s important to get to know your trees, perhaps keeping records?

Summary note 3.The general health of a tree must also dictate how much or little water it needs:- a sick tree, perhaps with rotting roots from overwatering, will be unable to take up water through damaged roots.

A further determining factor of how much to water a tree is its rate of ‘transpiration’ at that time. This is the transport system within the tree, carrying water and nutrients from root to leaf, then from leaf back down throughout the tree, to the roots and out to the awaiting mycelium (beneficial fungus in the soil). Transpiration only takes place when the tree is in leaf/needle/active growth. The rate of transpiration is controlled by small valves on the underside of each leaf called ‘stoma’ or ‘stomata’ which react to changes in sunlight, windspeed, temperature etc. (The stoma release waste gas, such as Oxygen.) All these need to be assessed before watering. Note: following defoliation, reduce watering! No leaves = no transpiration.

Some points to bear in mind when watering your healthy bonsai:

Give more water, more often, in the growing season than in the dormant season. Don’t water trees if frost is forecast. Plan a watering regime around the weather forecast. Don’t be tempted to miss watering if only light rain is forecast. This won’t be enough water to keep your trees healthy.

Water the soil thoroughly, till water trickles from the drainage holes, then ten minutes later, repeat the process. The Japanese bonsai growers say “for bonsai, it always rains twice”. Remember to ‘heft’ your trees before watering to gauge how much water each one needs. Overwatering is likely to kill your tree, just as under -watering, only more slowly!

Summary note 4. Don’t water in full sun. The evaporation rate is faster, often creating a crust on the root surface; the transpiration rate is faster, which allows less opportunity for the tree to extract nutrients from the solution; Watering in the early morning will be more efficient for the tree, as the stomata will be open and the transpiration process will be in full swing. Ensure the soil receives enough water.

Don’t water the flowers/blossom on a flowering tree, you’ll ruin them. If heavy rain is forecast, consider sheltering flowers from such a downpour. However, trees in flower will drop all their flowers if left too dry. Perhaps best not to plan a holiday for this season?

Summary note 5. Water less following root or leaf pruning, as reduced leaves mean less transpiration, as noted above. Pruned roots need to recover before they can take up moisture, but don’t let them dry out.

Summary note 6. Watering Pines at the wrong time may cause elongated needles in early season and candle growth season. Restrict watering of Pines until needles are fully open on candles. There are many varieties of Pines, so take the time to study your particular variety’s needs.

Summary note 7. Azaleas thrive best when misted frequently, but not in full sun or when frosty.

4.

If in any doubt, - ask! Ask more than one person, as you’re likely to get several different answers. Then you can adapt the advice given to your own circumstances. If you don’t belong to a bonsai club, you should consider joining. There are many clubs around the UK, 60 of which are registered with the Federation of British Bonsai Societies at www.fobbsbonsai.co.uk/information/members

Appendix 1. Soil pH and Nutrient availability.

1 7 14

Appendix 2

pH levels for trees and shrubs

Common Name Optimum pH Range

Trees and Shrubs

Apple 5.0-6.5

Ash 6.0-7.5

Azalea 4.5-6.0

Birch 5.0-6.5

Blackberry 5.0-6.0

Blueberry 4.0-6.0

Boxwood 6.0-7.5

Cherry, sour 6.0-7.0

Chestnut 5.0-6.5

Crab apple 6.0-7.5

Dogwood 5.0-7.0

Elder, box 6.0-8.0

Fir, balsam 5.0-6.0

Fir, Douglas 6.0-7.0

Hemlock 5.0-6.0

Hydrangea, blue-flowered 4.0-5.0

Hydrangea, pink-flowered 6.0-7.0

Juniper 5.0-6.0

Laurel, mountain 4.5-6.0

Lemon 6.0-7.5

Lilac 6.0-7.5

Maple, sugar 6.0-7.5

Oak, white 5.0-6.5

Orange 6.0-7.5

Peach 6.0-7.0

Pear 6.0-7.5

Pecan 6.4-8.0

Pine, red 5.0-6.0

Pine, white 4.5-6.0

Plum 6.0-8.0

Raspberry, red 5.5-7.0

Rhododendron 4.5-6.0

Spruce 5.0-6.0

Walnut, black 6.0-8.0

Willow 6.0-8.0

The Old Farmer’s Almanac 2019 (founded 1792)

Additionally, low pH trees include Berberis, most conifers, Cotoneaster, Hawthorn, Tree Heather, Ilex,

Lonicera, Magnolia.

‘Bibliography’.

Beautiful Bonsai. Bruno Delmer. 2002. Sterling Publishing Co. Inc.

Bonsai Basics. Colin Lewis. 2008. Octopus Publishing Gp. Ltd.

Bonsai for the Home and Garden. Leonard Webber. 1992. Bookmark Ltd.

Bonsai from Native Trees. Werner M. Busch. 1997. David & Charles Publishers.

Bonsai: The Art of Growing and Keeping Miniature Trees. Peter Chan. 1985. Apple Press

Ltd.

Bonsai: The Complete Guide to Art and Technique. Paul Lesniewicz. 1988. Blandford

Press.

Growing and Displaying Bonsai. Colin Lewis & Neil Sutherland. 1994. Aurora Books.

Satsuki. Alexander Kennedy. 1995. Troutbeck Press.

Satsuki Bonsai. Janine Droste. Undated. ISBN 978-94-90173-02-9. Bonsai Europe

Publications.

The Bonsai Book. The Definitive Illustrated Guide. Dan Barton 1994. Bookmart Ltd.

The Bonsai School. Craig Coussins. 2002. Silverdale Books.

The Bonsai Specialist. David Squire. 2004. New Holland Publishers (UK) Ltd.

The Complete Book of Bonsai. Harry Tomlinson. 1990. Dorling Kindersley Ltd.

The Creative Art of Bonsai. Isabelle & Remy Samson. 1994. Ward Lock Ltd.

The Essential Bonsai. Ken Norman. 2002. Anness Publishing Inc.

The MacDonald Encyclopedia of Bonsai. Gianfranco Giorgi. 1991. MacDonald & Co

(Publishers) Ltd.

(Other bonsai books contained similar advice, but added nothing on this subject to

those books above. Some books named specific products, but as products are removed

by law or formulations change, they have not been included here.)

Please note that many of these books are now dated and due to advances in

technology, not many paper books are being written. Most information is online or in

magazines.