A straight trunk is one of the basic forms of bonsai, characterized by a trunk that grows vertically upwards. This form is often seen in nature in ideal conditions where the wind is not too strong and there is good sunlight. The beauty of a straight trunk is judged by the condition of the moss, the arrangement of the branches, and the root spread. As it grows upwards, the trunk should become thinner, and the spacing between the branches should gradually decrease. It is also considered good for the branches to extend in all directions.
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