Create a Formal Upright Bonsai Tree
The formal upright bonsai is the classic style from which all other styles have evolved. A gently tapering trunk rises straight from the pot and a set of well developed roots. Branches begin ¼ to 1/3 of the way up the trunk. The bottommost branch should be the best developed, the branches becoming more delicate on the way up to provide a triangular outline.
Step 1: Choose Your Plant
Conifers are a natural choice for this style. A few deciduous tress can be trained to match, but avoid naturally bushy or irregular plants when planning a formal upright bonsai. Plants with lots of thin roots will not be able to provide the correct root structure.
You can begin with a sapling, but it will take longer to develop. A tree with a good trunk thickness that is otherwise too tall can sometimes be cut down, so it is worth considering.
Step 2: The Roots
Formal upright bonsai should give the illusion of being a towering giant in the forest, so a well-developed, visible root structure is a must. You can trim the deeper root elements while repotting to encourage the growth of the surface roots. This process may take a few cycles to perfect, but keep trying. Provide lots of water and a good fertilizer to ensure the remaining roots carry enough nutrients to the tree.
Step 4: The Trunk
Growing your tree outside for a few years in the ground is a great way to get a thicker trunk. Unfortunately, it may grow your tree taller than you want. Another trick to try is wrapping a coil of wire around the trunk. Push it down until it presses tight against the bark. This will trap the sap below the wire and thicken the trunk at that point. Gradually move the coil up to create a thickening up and down the length of the trunk. Remember, you're looking for a tapering trunk.
Step 5: Branches
Remove small twigs in the bottom ¼ to 1/3 of the trunk. This area should be clear of branches.
The bottommost branch should be the thickest and most developed, as though the tree had grown it first. Try using the wire trick if this is not true.
Branches should not point straight at the viewer, but rather jut mostly out to the sides. The front and back can be filled in by offshoots of the main branches.
Branches near the bottom of the tree should be pointed slightly downwards, branches near the top slightly upwards. Try wiring your branches to change the angle if they do not naturally go the direction you want, but avoid extreme bends that do not look like natural growth.
Flaws in the structure of your tree can be covered by making it look like an older tree that has been damaged by the elements. For a tree that is too tall, strip the bark off the top and shave it to a point or create a craggy break to give the impression of die off or lightening strike. Explain a weak root structure by carving out the base of the tree to give the impression it was hollowed by fire. Just remember to provide a rot preventing measure whenever you damage the bark of your tree.