Bonsai cultivation and care
Trees are difficult to cultivate in containers, which restrict root growth, nutrition uptake, and resources for transpiration (primarily soil moisture).
In addition to the root constraints of containers, bonsai trunks, branches, and foliage are extensively shaped and manipulated to meet aesthetic goals.
[2] Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species[2] which produces true branches and remains small through pot confinement with crown and root pruning.
Bonsai practice is an unusual form of plant cultivation in that growth from seeds is rarely used to obtain source material.
To display the characteristic aged appearance of a bonsai within a reasonable time, the source plant is often partially grown or mature stock.
Alternatively, it may be selected for non-aesthetic reasons, such as known hardiness for the grower's local climate or low cost (as in the case of collected materials).
[2] While any form of plant propagation could generate bonsai material, a few techniques are favored because they can quickly produce a relatively mature trunk with well-placed branches.
The grower trains the source specimens to a greater or lesser extent before sale, and the trees may be ready for display as soon as they are bought.
Nursery stock is usually young but fully viable, and is often potted with sufficient soil to allow plants to survive a season or two before being transplanted into a more permanent location.
Collecting may involve wild materials from naturally treed areas, or cultivated specimens found growing in private yards and gardens.
For example, mature landscape plants being discarded from a building site can provide excellent material for bonsai.
Hedgerow trees, grown for many years but continually trimmed to hedge height, provide heavy, gnarled trunks for bonsai collectors.
Some of the difficulties of collecting include finding suitable specimens, getting permission to remove them, and the challenges of keeping a mature tree alive while transplanting it to a bonsai pot.
[4] Bonsai are carefully styled to maintain miniaturization, to suggest age, and to meet the artist's aesthetic goals.
In bonsai, however, the artist has close control over every feature of the tree, because it is small and (in its container) easily moved and worked on.
In contrast, in a bonsai being prepared for display, each leaf or needle may be subject to decision regarding pruning or retention, and every branch and twig may be formed and wired into place each year.
A common aesthetic technique in bonsai design is to expose the tree's branches below groups of leaves or needles (sometimes called "pads") by removing downward-growing material.
Along with pruning, leaf trimming is the most common activity used for bonsai development and maintenance, and the one that occurs most frequently during the year.
Careful pruning throughout the tree's life is necessary, however, to maintain a bonsai's basic design, which can otherwise disappear behind the uncontrolled natural growth of branches and leaves.
[5] For larger specimens, or species with stiffer wood, bonsai artists also use mechanical devices for shaping trunks and branches.
The most common are screw-based clamps, which can straighten or bend a part of the bonsai using much greater force than wiring can supply.
[5] In this technique, new growing material (typically a bud, branch, or root) is introduced to a prepared area under the bark of the tree.
[6][7] Short-term dwarfing of foliage can be accomplished in certain deciduous bonsai by partial or total defoliation of the plant partway through the growing season.
Shari denotes stripping bark from areas of the trunk to simulate natural scarring from a broken limb or lightning strike.
Only during their dormant period can they safely be brought indoors, and even then the plants require cold temperatures, reduced watering, and lighting that approximates the number of hours the sun is visible.
Raising the temperature or providing more hours of light than available from natural daylight can cause the bonsai to break dormancy, which often weakens or kills it.
Other tools include branch bending jacks, wire pliers and shears of different proportions for performing detail and rough shaping.
The inorganic components provide mechanical support for bonsai roots, and—in the case of fired clay materials—also serve to retain moisture.
Varieties such as akadama, or "red ball" soil, and kanuma, a type of yellow pumice used for azaleas and other calcifuges, are used by many bonsai growers.
In practice, this means that trees from a hardiness zone closely matching the grower's location will generally be the easiest to grow, and others will require more work or will not be viable at all.
