Espalier | noun | es-pal-ier : a plant (such as a fruit tree) trained to grow flat against a support (such as a wall).
They always catch my eye—even before I knew what to call them, I thought they were very attractive. I’ve learned that they have ancient roots and were a prominent feature in medieval monastic life because they could be grown in small spaces. And while most espaliers are fruit trees, roses and other plants with woody stems can be trained in this way as well. There are, also, many designs and patterns used in the art of espalier.
The ones pictured above are at Ladew Topiary gardens, where topiary, another art form for shaping trees into ornamental shapes is prominent, but where some espalier are also found.
Here is a link to an excellent article about how to master the art of the espalier.