UK gardening help and assistance

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Bonsai - general growing and care

Bonsai Care

For Horticultural beginners a few words about fertiliser for Bonsai are probably beneficial. Plants require carbon which they take from carbon dioxide using photosynthesis. This is essentially the majority of their structure (a carbon based life form). Fertilisers are trace metals which they also require but in much smaller quantities. The main three are Nitrogen (N) Phosphorous (P) and Pottasium (K). Others include Manganese Boron and so on, which are required in quantities much smaller than the main three (NPK). Potting soil will undoubtedly contain some trace metals but these will be used by the plant within a few months. Nitrogen is the most important element and is required for vegetative growth. Pottasium and Phosphorous are needed when plants are flowering or fruiting.

Applying these principles to our bonsai it is best to apply a general fertiliser from spring to autumn unless you are growing a variety which is averse to lime in which case you should choose a more specific fertiliser. In late Autumn you should switch to one with less nitrogen as growth is slower in Winter

Particularly for beginners, solid fertilisers are easier to manage than liquid versions as they break down slowly each time they are watered. Too much fertiliser can cause a variety of Bonsai problems and some are difficult or impossible to recover from. If you do not feed your bonsai it will probably not die but will certainly not flourish. Too much fertiliser can burn a Bonsai plant.

Outdoor Bonsai

Although bonsai originated in China (or possibly India), it is thought to have become an art form when it was exported to Japan. Today it is more closely associated with Japan and most accessories (pots and tools etc) are made in Japan. In fact many of the Bonsai trees themselves that are bought and sold in Europe have been imported from Japan. It is commonly thought that Bonsai are delicate and fragile plants that must be kept indoors at all times. This is untrue as the more traditional varieties favoured by bonsai enthusiasts tend to be hardier species such as Conifers, which grow naturally outside . Japanese bonsai are all outdoor bonsai, as is traditional in the art form. They are usually hardy trees and shrubs which makes them suited to European Climates as well as Eastern Climates.

Indoor Bonsai

Bonsai are often kept indoors by people who have bought or been given a Bonsai tree in the mistaken belief that it is just for decoration. This is a common cause of death which is somewhat inevitable when the plant is not bought from a Bonsai Nursery with no informed advice given about the needs of the plant. In Japan bonsai are often brought inside for a few days at a time for decoration but this is not how they are kept permanently. Bonsai varieties which do not suit temperate climates are becoming increasingly popular however as many new enthusiasts either have no outside space suitable for bonsai, or wish to have their tree visible at all times.

Indoor varieties often adhere to the style principles of Chinese bonsai and include more tropical species of plants and trees. Some consider this newer art form as not true bonsai. Traditionally bonsai are dwarfed varieties of trees and shrubs that survive well outside in temperate climates, but would not do so well indoors. Indoor varieties of bonsai originate from more tropical regions and would not survive being left outdoors in Temperate climates such as Europe or North America. Although Outdoor bonsai are generally easier to keep, many beginners like to start with an indoor variety which they can see all the time. Indoor bonsai are also used to decorate a room in your own unique style and are associated with a minimalist or Zen style of decor.

Bonsai Pots

The pot is a major part of the aesthetic of Bonsai plant as a whole and must reflect that. Both practical and aesthetic factors need to be considered. For a pot to be practically suitable for your bonsai plant it should:

  • Be large enough to allow the roots to develop over two years, but not so large that the roots can become waterlogged.
  • Be frost proof (for Outdoor varieties) and have enough drainage holes.
  • Usually be shallow, but should be deeper if the tree has fruit which requires more water, or if it is a cascading variety, in which case the pot is narrow and deep.

Aesthetic factors are more open to interpretation as it depends on your own style and taste, but there are some general guidelines:

  • The pot should balance the tree's height and spread. Between two thirds and three quarters of the trees height or width (depending on which feature is dominant) is generally considered appropriate. Denser foliage also requires a slightly deeper pot.
  • Pots and trees can be considered male or female. An oval or round pot is more feminine, and therefore suited to more delicate trees. Pots with strong edges suit trees with a more masculine look.
  • Trees in oval or rectangular pots look more natural when set to one side of the pot, in the ratio 1:2. A tree with a slanted trunk should also be set slightly to one side so that the bulk of the tree is centered rather than the base.
  • The outside of the pot can be glazed or unglazed. An unglazed pot with earthy tones is usually recommended but a skillfully chosen colour can enhance the beauty of the tree.

Bonsai Soil

There are many different soil mixtures which each have different properties as plants have varying needs from the soil they stand in.  The soil gives the plants roots access to water, air and nutrients. Some plants for instance thrive best in soil which allows them more access to water than oxygen, so a soil with more moisture retaining qualities is preffered by the plant. In bonsai soil there are four main ingredients:

  • Sand - Used to help the soil take in water. Little is used as the surface would dry out much more quickly than the rest, leading to over watering. Lava granules, or perlag can be used to much the same effect, but allows more access to air than sand.
  • Peat - commonly used to retain water. It is often prepared with fertiliser such as lime as it has no nutrients itself. Humus is also used to the same effect and this does contain nutrients.
  • Loam - holds water well but not so much as to leave the bonsai plant in standing water, and then gives it off slowly along with nutrients. Soil with alot of loam will compact quickly when dry.  Akadama is a granular loam from Japan which does not suffer the same problem. It can be used to replace loam in the soil mixture or even as the sole medium for your trees.
  • Granite grit - small stones added to allow the drainage of water.

Bonsai trees generally thrive in one of three different soil mixes. Look for your tree in one of the recommended books for a species guide to tell which is the best soil for your plant:

  • Basic soil mix - One part loam, Two parts peat, Two parts granite grit  - Good for most plants.
  • Free draining soil mix - One part loam, One part peat, Two parts granite grit - Good for plants which require less water.
  • Lime free (ericaceous) soil mix - One part loam, Three parts peat, One part granite grit - Recommended for lime-hating plants.

Bonsai Tools

There are many tools available to assist you in maintaining a bonsai and it can be difficult to know what you need. Many tools will not be needed by a beginner and they can be expensive, so it is best to be sure of what you need before you commit to buying. Tools can vary widely in price due to the range of quality available. Generally you get what you pay for, and a cheap set of tools will not be of great quality. It is best to buy one or two high quality tools to start with, and build a collection as you go. Let's start with some basics.

The tools you will need depend on what sort of work you intend to do. You will need only a few tools to prune or repot a bonsai, whereas to sculpt a bonsai from a larger tree requires more tools. Household items can also be useful and inexpensive tools in crafting bonsai. First determine what you intend to do to your bonsai, and then pick your tools accordingly:

  • Concave branch cutters - used to sever branches large and small (with correspeonding tool sizes). They leave a concave incision mark which is for aesthetic purposes, as well as assisting in the healing of the wound.
  • Spherical knob cutters - tidy up old wounds and the stubs of branches.
  • Wound sealant - applied after a branch is cut to prevent infection entering the wound. Japanese cut paste is popular as it can be easily removed afterwards.
  • Scissors - have many uses. Leaf scissors are for trimming leaves, slightly stronger scissors for medium sized shoots and heavy duty scissors for thicker shoots. Using scissors too small for the job can bend the blades and leave them unable to make clean cuts.
  • Wire - used to train branches to a specified shape. General wire working tools such as pliers and wire cutters are perfectly suitable, but specialist tools can also be useful. Jinning pliers for example are used to tear wood from the trunk.
  • Root hook - draws out soil from roots when repotting. A chopstick can also be used to much the same effect, as well as replacing soil into the rootball.
  • Other less common tools include bending jacks for more extreme manipulation, a folding saw to cut branches without squeezing them, a soft brush for tidying and a turntable for easy access to all angles.

Tools should be kept clean and dry or else they could become damaged or spread disease. As well as ensuring the correct tool size, care should be taken when using cutting tools near the base as soil and grit can chip the blades, making them ineffective and preventing clean cuts.

Buying Bonsai

The quickest way to obtain a fully formed bonsai is to buy one from a specialist nursery. This is by far the easiest way to own a fully formed bonsai tree but it is not without its pitfalls. Some of the more common problems to look out for are:

  • Cost - Fully grown bonsai can be very expensive, partly because of their age but also because they are likely to have been imported from countries in Asia and their price also includes shipping and handling costs.
  • Availability - although many Garden Centres have a small selection of bonsai they can tend to be of poorer quality as staff are unaware of how to care for them appropiately, and sometimes young trees that are grown in pots are sold as bonsai. Specialist Nursery's can be few and far between so you may have to travel far to reach one.
  • Quality - Some knowledge of bonsai is needed to ensure that the plant is of good quality before buying. An unhealthy plant or one placed in poor quality soil is unlikely to survive very long, particularly without a great deal of knowledge and experience in caring for that particular species. If you know someone who has some experience in raising bonsai it would be extremely helpful to you if you could bring them with you when you go to purchase a plant.