The group setting, or forest, has an uneven number of trees, usually of the same style and species with variation in size. Here are some simple facts from two important Bonsai textbooks that can be helpful when making a forest planting.
From Bonsai by Deborah R. Koreshoff and Bonsai Techniques I John Naka.
(1) Odd number when using 3-9 trees. When the numbers are more than 9 it is sometimes called multiple plantings. If many trees are used, it is acceptable to use an even number.
(2) The trees are placed off center 1⁄3 of the way along the pot creating asymmetry.
(3) Trees should all slant in the same direction. One exception to this rule is the fanned out setting.
(4) If the direction of the slant is to the right, the largest tree and greatest number should be planted on the left, while the smallest trees and the more spacious feeling should exist on the right.
(5) Height should be different as well as trunk thickness as this will create depth.
(6) When viewing from the front and the side, no two trees should be in line. These points create depth and variety which are found in nature.
(7) Choice of container is in relation to the size of the tallest tree. The container should be abut 2⁄3 the size of the longest tree. Generally it is oval, rectangular, or free-form and of shallow depth. Medium depth pots are used for thick stocky trees.
(1) First work out a design you are aiming for on paper. Roughly sketch the position of your trees and the most important ones are the #1, #2, and #3 trees since they will give you the general direction of your asymmetrical triangle.
(2) Remember that the tallest trees are in front, medium trees are in the middle and the smallest are in the back. This will give a better perspective (a close up view forest will have the trees placed in reverse order).
(3) Begin to style your main tree, even #2.
(4) Prepare your pot with the necessary tie downs using wire or string.
(5) Remove your trees from the nursery pots and root prune. Place them in the pot in their positions.
(6) If you are satisfied with their position, tie them down and fill the pot with Bonsai soil.
(7) Make any other additions such as a “stream”, or rocks, or other decorative material. However, there are those that say to resist the desire to add figurines if you wish your design to be in the Japanese mode, otherwise, it will be a Chinese Penjing.