Geometric gardens are laid out in basic geometric shapes, such as a circle, square or rectangle. The shape is then divided into four equal parts, and each part is planted with the same combination of herbs or plants that complement each other.
Unity in the geometric garden is achieved through a repetition of form, color and texture. For instance, if you plant the outer edge of a circle with an upright growing herb, such as mountain chives, plant the outer edge of the portion of the circle opposite with mountain chives or an herb with a similar upright growing habit, such as curly parsley. This will create a sense of balance.
Consider using a color scheme in your geometric herb garden to provide a sense of cohesion. Using three colors will keep it simple, such as green, gold and burgundy or silver, maroon and dark green.