Repetition while being related to rhythm is separate, as it involves the repeated use of identical entities within your garden design. While a rhythm may be established using many different elements, repetition by it’s nature uses elements that are exactly the same.
Practically any design element that is at your disposal can again be used here; Colour, texture, form, shape, line or point can be employed. Do however be careful not to overuse repetition as it can cause your design to become mundane and, especially in smaller gardens, can effectively reduce the apparent size of the space.
One of the most effective tools at your disposal when seeking to create a unified design, is, along with mass plantings, repetition. A good design is one where nothing else remains to be taken away. Repeating elements within you scheme can be of great assistance to you in helping to reduce the amounts of materials that you use.
Repeated use of one particular plant in your scheme such as a particular type of tree or a shrub can give you a year round element of repetition. Using trees and shrubs will also give you some variation as these change colour and may loose their leaves during the seasons. If you decide to repeat bulb and herbaceous plantings you will have a repetitive element that appears and reappears during the growing seasons.
Using your hard landscape material is a useful tool here also. By repeating elements of your paving scheme or indeed allowing a line of fence-posts to be visible you are setting up a repetitive pattern that will help to improve the visual success of your garden.
The private house above shows the repetition of a single colour and Monets Garden repeats the use of his water lillies across the pond. Both have a strong unifying influence.
Tip: Never use too many different types of materials in you design scheme. Always, throughout the process, examine ways of taking one material or another out of your scheme before looking to see if it will help you to strengthen the overall visual appeal. your design is finished when it looks good and there is nothing left to take away.