The penstemon varieties grown in gardens are mostly bushy plants that send the flowering shoots up to about waist level. The size makes them suitable for use in most gardens. They are related to foxgloves, being in the same family, and generally begin to flower as the foxgloves go over. However, while foxgloves are a plant for sunshine or light shade, penstemon is a plant for full sunshine. Though similar to the foxglove, the trumpet-shaped flowers are not as long as those of the foxglove and they flare more at the mouth. The penstemon flowers are also carried on a spire-shaped flower stem but these are not as rigid or as tall as the foxglove. Penstemon has a wide range of colours from white and palest pink, bright scarlet-red and pale blue-purple to deep blackberry colours, a colour palette that is much more varied than foxglove and has been achieved by crossing species and selecting the best.

In the past, it was not unusual for nurserymen to change the names of German or French varieties