AS 2303:2018 pdf free.Tree stock for landscape use.
4.2.10 Included bark Included bark shall not be present. The stem bark ridge and branch bark ridge unions shall be convex (outwardly turned and extruding). See Figure 4.6[a) and [C). NOTE Included bark may be an inherent characteristic of various species and can arise through genetics, the use of poor pruning practices or it may be associated with regrowth after damage. Unions with included bark inwardly turned [see Figure 4.6[b) and (d]] are generally more prone to failure than sound/convex unions. They represent an inherent risk, which is greater in larger trees. Included bark can often be managed by formative pruning during nursery production and through the exclusion of stock plants that exhibit inclusions. While there may be some species that naturally exhibit junctions with included bark, which rarely fail, these exceptions should be dealt with on an individual basis and should not compromise the overall aim of eliminating included bark from tree stock. At each stage of production the root system should be inspected for non-conforming roots and pruned if required.
Section 5 Tree stock balance assessment
5.1 General
Tree stock balance is used for guidance to assess the proportional balance of tree stock grown in containers  20 L or ex-ground tree stock with a minimum rootball diameter of  400 mm. It describes the proportional relationship between the above-ground and below-ground portions of tree stock and can have a significant impact on the development of quality tree stock. Tree stock height and calliper (expressed as size index) and rootball volume are interlinked and form the key elements of tree stock balance.
Sufficient rootball volume contributes to the ability of tree stock to support itself in the landscape. It results in a reduction of artificial supports and structures and enables tree stock to be grown at wider spacings. Tree stock balance is also useful to ensure that tree stock has not outgrown its container or been dug ex-ground with too small a rootball. It can also be used to ensure that tree stock has sufficiently grown into its container (see Clause 4.3.6), inform irrigation regimes, and potting processes within production nurseries. AS 2303 pdf download.