Penstemons, also known as beard tongues, are perennial flowering plants with long, tubular flowers that appear on tall flower spikes in spring or summer. Penstemon flowers can be white, pink, purple or red in color, and are prized for the ornamental value they impart to the garden. Penstemons are easy to grow and require very little care once established. They thrive in high light, low moisture situations, which makes them ideal for rock gardens. Penstemons, however, also perform well as bedding plants with the proper maintenance.
Plant penstemons in spring after all danger of frost has passed. Select a planting area that receives full sun and has well-drained, gravelly soil. Avoid heavy clay soils, as penstemon plants prefer dry growing conditions and need very good drainage to survive.
Dig a hole two to three times wider than the growing container and of equal depth, place the penstemon plant in the hole so that it sits slightly above the soil line, and then back-fill with hole with soil. Compact the soil with your hands to remove any air bubbles.
Apply a thin, 1-inch layer of mulch to the soil surrounding penstemons just after planting. Use gravel to mulch dryland and rock garden penstemons. Use shredded bark mulch or organic compost to mulch all other types of penstemon plants.
Water penstemons once every two to four days for the first three weeks of growth. Reduce watering to once every four to seven days until the plants become established, usually about two months. Water established penstemon plants once every two weeks in spring and fall and once every week in summer. Do not provide supplemental water in winter.
Remove spent blooms promptly after they begin to fade to promote the longevity of penstemons and encourage further blooming. Snip the flowers off using your fingers or pruning shears. Leave one or two flower stalks to set seed if reseeding is desired. Otherwise, remove all faded blossoms.