How to Grow Beardtongue (Penstemon)

Beardtongues (Penstemon spp.) range from soaring spires to ground huggers, with native species found from coast to coast. As diverse as their natural habitats, their hardiness spans U.S. Department of Agriculture plant hardiness zones 3 through 10. Beardtongues accommodate varied conditions, but they flourish in gardens similar to their native soil, precipitation and climate. Low-maintenance, but often short-lived, many beardtongues share basic preferences.

Most beardtongues prefer at least six to eight hours of full, direct sun each day. In general, more sun increases bloom quantity and enhances vibrant colors. Tall varieties that require staking in shade grow strong, erect and self-supporting in sun. For beardtongues out of their native locales, higher elevations and hotter climates demand more sun protection. Eastern species, for example, bloom better and longer given partial shade. Western varieties tend to prefer south- and west-facing exposures. Allow for a plant's mature width plus 4 to 6 inches between it and neighboring plants. Good air circulation helps prevent disease.

Beardtongues universally prefer fast-draining, porous, well-aerated soil. Excellent drainage is critical to prolonging their lives. Soil pH in the near-neutral to slightly alkaline range suits most species. Improve soil structure with a very light addition of well-aged, organic compost or leaf mold; a 1-inch layer worked into the soil before planting is sufficient. Many beardtongues live just two to three years, and rich, moisture-retentive garden soil shortens lifespans rather than lengthening them. Cultivars of beardlip penstemon (Penstemon barbatus cvs., USDA zones 3 through 9) adapt well to average garden conditions.

Natural precipitation provides the moisture needs for locally native beardtongues and xeric varieties. Established plants rarely need supplemental water. In general, deep-rooted beardtongues have greater drought tolerance and lower moisture needs than other familiar garden perennials. Rocky Mountain beardtongue (Penstemon strictus, USDA zones 4 through 9) tolerates higher moisture. Poor, lean, infertile soil without added fertilizer suits most beardtongues best. If desired, a thin topdressing of organic compost adds gentle, slow-release nutrition and improves soil. Use a light hand, and keep compost away from the crown. Avoid fast-acting, high-nitrogen fertilizers.

In areas matched to their natural habitats, beardtongues generally don't need extra winter protection, but they often rely on snow cover to guard against winter cold. If snow is lacking, other protection may be needed. Avoid water-retentive mulch that can keep beardtongue crowns overly wet. Nonabsorbent mulch, such as shredded bark, pine needles and landscape gravel, regulate soil temps without adding moisture. Rose-cone-type protection placed over crowns and covered with leaves provides winter insulation as well. Cut beardtongues back in fall or in early spring before new growth begins. Use sharp garden shears, and sterilize the blades with household disinfectant before and after your work.