Traditional Perennial Border If you want to interplant with other garden classics and you live in an area that has a fairly mild climate, Zone 6 and above, you will probably want to select from the large-flowered European hybrids, west coast and eastern species and their cultivars. If you live in an area that has a more severe climate, Zone 5 and below, you will want Canadian and US hybrids, northern, mid-western and eastern species and their cultivars. The zone you are in does not tell you everything about what you will be able to grow, but it is a first indicator to assist beginners in selecting species. Generally it is best to start with plants that are widely available in local nurseries.

     Pots and Containers There are penstemons that will perform well in pots and bloom for a long time where the air is moderately humid. They may be discarded at the end of the outdoor season or severely cut back and brought into a cool storage area. The ones called Penstemon 'Gloxinoides' or European Hybrids and bedding types come in a riot of colors on the red side of the spectrum from deepest purple to the palest pink and white. Beautiful orchid and blue Penstemon heterophyllus and its named cultivars are also good choices for pot culture.

     Annuals Some penstemons can be used as annual bedding plants. They are half-hardy hybrid strains that come in many colors and heights. They bloom for a very long period and perform best in areas with a long, mild summer and fall. A few are hardier than others and may live and thrive for several years. Seeds need to be started in late fall and early winter in mild climates, or plants may be purchased and set out after the weather has settled. Look particularly for seed mixtures that have been bred for fully round, multi-stemmed plants. Those mentioned for use in pots are also useful as annuals.

     Rock Gardens, Slopes and Raised Beds These sites provide ideal conditions for the greatest variety of species. You need to decide whether you will keep it fairly dry or water regularly. This will influence your selection of species to grow. Those from the northern states and alpine areas will perform better if watered regularly by normal precipitation or irrigation, especially in the spring. Those from normally arid regions can perform well if watered infrequently, perhaps not at all! This will depend on your soil and precipitation. In general, the size of the rocks you have available and the size of the garden will determine which species will be best for you. With boulder-sized rocks, you can use penstemons that grow two to five feet tall! Large rocks can also be used to shelter smaller plants from full sun. Many penstemon species are particularly good in these situations because they have evergreen basal leaves that are attractive through the winter. They might turn a rich maroon or be covered with a downy surface that reflects light. There are also many with leaves in shades of gray, gray-blue and gray-green and almost white.

     Troughs should be considered by those who are fond of miniature plants, don't have much room or cannot stoop to tend a garden. They are containers made of concrete, peat and perlite in any shape and 6-10 inches deep, that are usually raised off the ground so that tiny leaves and flowers can be appreciated without kneeling. The top of a stone retaining wall with crevices between stones offers a similar possibility. There are many charming small penstemon species that fit either type of location.

Selecting, Growing and Caring for Penstemons
From Chapter 41

Lindgren, Dale and Wilde, Ellen. 2003. Growing Penstemons: Species, Cultivars and Hybrids: American Penstemon Society. 519 West Lancaster Avenue, Haverford, PA 19041-1413 : pp. 105-110