Three's company in the garden

One of the principles of good landscape design is to plant things in odd numbers - threes, fives and so on.
I have no idea who dreamed this up or why, but many landscapers stick quite firmly to this rule.
A designer friend told me: "Traditionally we don't tend to plant in even numbers because we want to avoid plants lined up in a row like soldiers. We take our inspiration from nature, which has a natural chaos about it."
And it works, whether you're applying it to plants or containers and other elements of hard landscaping.
If you want to create a focal point, fill a gap or disguise something ugly, select three similar containers and position them close together.
Even three old pieces of sandstone or block will give you a special look. There's something magical about it.