Pretty petunias in a not-so-pretty container.

In recent weeks, I’ve offered several ideas about pot combinations, and have talked a little about design within the pots. However, I have not yet discussed the basics of container design.

There are three basic principles when you are combining plants within a container: You need a vertical element, a mass or featured element, and filler elements, which might be cascading.

I always think of the vertical plant as one that provides the stature or structural backbone. The upright plant will be the tallest in the pot, of course. I often use a perennial, but some tall annuals can work as well. This plant is at the back or at the center of the pot, depending on your focal points.

Speaking of the focal point: The mass or featured plants should be placed at that focal point. They are what draws the eye to the pot, either with strong flower color or foliage; you want large flowers or leaves to make a bold statement.

Filler or trailing plants finish the look off, generally in the front of the pot and/or on the sides. I love to find successful trailing plants that cascade over the pot, covering it to some degree. If the trailing plants have flowers, you want them to be of a smaller size and in contrast to the focal-plant colors and texture.

If you only have 20 minutes in your desert potted garden this week: If you have petunias, the long growth period can make them leggy. Cut them back to where you see new growth, and they will last nicely for another two to three months!

Marylee is the founder and former owner of The Contained Gardener in Tucson, Ariz. She has become known as the Desert’s Potted Garden Expert. E-mail her with comments and questions at potteddesert@gmail.com, and follow The Potted Desert on Facebook.