Balance is a principle of all art forms and landscape design. While there may be just a little bit more to it, this is how I can explain it to make it simpler for first timer landscapers and do it people that do it themselves to understand.
A garden, landscape, or any form of the same proportions would naturally feel and look balanced. However, many gardens and landscapes are not exact or symmetrical in their shape. They’re asymmetrical in form and are usually without any natural balance of their own. So landscaping relies on other elements to create balance through unity.
A lot of times, a lack of balance is directly related to a lack of repetition. Repeating alike elements such as plants or rocks throughout the landscaping will help unify different areas to others. As little as one repeated matching plant group, color, piece of decor, or hardscape may accomplish this.
A lack of balance is also created by placing surplus or all non matching elements throughout a landscape design. This can many times seem cluttered and unkept when it grows in. In the beginning of your design, plan for less; place just a few matching plant groups throughout the garden, and keep decor matching and to a small amount. You can add some more of it later.
A lot of the questions about landscape design deal with the shape of a design. Shape is unique to each design and will absolutely follow all of the necessary paths. However, any shape or form can be filled with elements and still be dull, void, loud, cluttered, and unbalanced. Balance isn’t necessarily dependant on shape. It can be but it is not most of the time. So do not get too hung up on attempting to even things out entirely by shape.
Landscape design is an art form and so it deals with the same principles that other art forms do. Repetition, unity, and balance are all important principles of art that go hand in hand with one another.
An architect use repetition in design by making doors, windows, fixtures, trims, all the same sizes, shapes, and styles. Imagine your home if every door, door frame, window, and fixture were of different sizes, shapes, colors, and types. It would be weird and chaotic.
And so it is the same with landscape design.
In order to create balance and comfort in a landscape that is lacking, you need to create some form of repetition. As small as one matching element placed on an opposite can create some sense of unity and consistency.
It is easiest and usually created in the softscape (plants, ornaments, lawn, decor, etc.). However, it should be considered in the hardscape (walks, driveways, necessities, fences, walls, raised beds, boundaries, etc.) of your drawn design plan.