Imagine yourself in the middle of the African savanna. Acaccia trees in endless fields of grass, with slow moving herds of Wildebeeste, Zebra and Giraffe. Passing herbivores nibble on the branches within reach, resulting in only the highest branches having foliage.
This style originates from South Africa, and is not part of the formal bonsai styles as developed in Japan. This means there are no special rules to this style. The single trunk may go straight up, and or have a few twists and turns. The trunk gradually dissolves in branches that widen into the canopy. This in turn is reltively wide in comparison to the height of the tree, with a fairly flat to and bottom.