Plant library · Perennial Flowers
Penstemon spp.
Penstemon brings tubular flowers on upright stems to sunny perennial beds from late spring into midsummer. At about 2 1/2 feet tall, it supplies a vertical flowering layer without becoming a large shrub-like presence. Its 18-inch mature width suits repeating drifts, small groups, and open pockets among lower plants. The flowers also make this a useful choice where pollinator activity is part of the planting plan.
Place penstemon in the middle of a border, behind low edging plants and ahead of taller summer perennials. Its upright stems read best where they can rise above neighboring foliage rather than being buried in a dense planting. Repeat it in a loose ribbon beside a path or across the front half of a sunny bed, leaving a clear reach-in edge for deadheading and seasonal cleanup. Keep the planting away from places that stay wet after rain or irrigation.
Set plants 18 inches apart, center to center. That spacing matches the roughly 18-inch mature width, allowing individual clumps to meet lightly while preserving air and access between stems. For a more defined drift, arrange plants in staggered rows rather than a single straight line. Reserve a band about 2 1/2 feet deep where the planting sits beside a path, wall, or the front edge of a mixed border.
Use penstemon in full sun, where its upright flowering stems can hold their place in a bright border. Lean, well-drained soil fits its low-water needs, making it better suited to beds that are not regularly saturated. In a mixed planting, place it with plants that can share the same restrained watering pattern. Avoid locating it at the bottom of a slope, beside a downspout, or in an irrigation-heavy pocket.
The main display runs from late spring through midsummer, so use penstemon to bridge the shift from spring bloomers into the summer border. Leave enough room around each clump for flowering stems to remain visible as nearby plants expand. Its perennial framework can stay in the plan from year to year across USDA hardiness zones 3 through 9, while the bloom window occupies only part of the growing season.
Penstemon is a broad genus with species and cultivars that differ substantially in height, spread, and habit. Use this footprint for the selected plant, but check any named variety before substituting it into a scaled plan. Full sun and freely draining soil remain important placement filters; heavy, persistently wet ground is a poor fit for the genus.[1][2]
Editorial content updated 2026-07-20.