The cascade style or kengai is basically a style in which the bonsai trunk and crown growing downward and below the level of its container. The overall shape of the cascade is triangular with long flowing branches. This cascading tree form is not frequently found in nature, except along streams or cliffs, but it is still a coveted style due to its relative complexity. It denotes a tree growing vigorously along a meandering stream with overhanging branches seeking to touch the water, or overhanging a rocky cliff edge.
As a beginner, you are not advised to train your bonsai in the cascading style until you have mastered the upright styles. For the cascade style, you will need to know about wiring since you will be using it quite a lot in order to bend the trunk and branches at first.
The pot or container in which to train the bonsai tree needs to be heavy and deep in order to balance gravity when the tree starts to lean over to one side. To remove obstacles from growth in this direction, it’s important that the tree and pot be placed near the edge of a table or bench so the trunk can hang below the container horizontally.
As the trunk is encouraged to grow in the downward U-shape, branches should be trained to sprout horizontally to give the tree a full appearance. Planting directly in the center, not near the edge of the pot, is the standard practice.
Often the tree will be trained to grow up and over, rather than simply over the edge. This gives a flow to the look and is accompanied by a tip that resides directly above the center. The trunk practically grows forward out of the pot and should be visually, “a little to one side”. Branches should be trimmed to create a ‘stair-step’ pattern to complement the cascade and give it a ‘meandering river’ look.
Since the trunk and several branches will be located below the container level, extra care is required to ensure that all receive adequate water and nutrients. Foliar feeding (applying fertilizer solution by spraying leaves or needles, which is then absorbed by the foliage) is a recommended way to feed the tree, since gravity may affect the flow and movement of water and nutrients to the leaves themselves.
Shrubby species like Azalea and Grapevine are the best species to use for the cascade style. A good woody tree species for the cascade style is the Bald Cypress. In general though, many kinds of species are able to be trained to cascade, but the pine species’ are least suited due to their naturally straight trunk. Nowadays, many artists cascade their bonsai trees by just training the major lower branches, and only slanting the trunk somewhat. This is considered a more natural way of cascading a bonsai tree.