I started the garden pictured on your left about three years ago, and the idea to create this space was almost accidental. I had a spot that used to contain a rotting tree stump, and I had some flagstones that were collecting dust in another corner of the yard, and I decided to see if I could turn the space into something besides another patch of lawn.
When I selected my initial perennials for perennials for the space, I did not take into account soil pH and sunlight needs, and I was consequently disappointed when the purple fountain ornamental grass I planted did not return. The next year I went with some Stella d'oro lilies and some bright red Asiatic lilies. In the center I added a Rose of Sharon plant, and during the spring there are some daffodils and tulips for early color.
Of course, it was another two years before the plants in this space filled out to the point where I achieved something like a wall of color. Thus, this garden took about four years to emerge as a colorful source for peaceful contemplation, though the happy accidents are more fun than simply filling the space with a bunch of annuals each year.