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Perennials of the Plantaginaceae family, the penstemons cultivated in gardens are mostly complex hybrids derived from North American species, mainly Penstemon hartwegii, P. campanulatus and their relatives. These crosses, developed mainly in Great Britain from the 19th century, have given rise to a considerable range of cultivars with extended colors, ranging from pure white to scarlet red through pink, magenta, violet, and purple.
The plants form upright clumps of 40 to 80 cm depending on the selections, bearing narrow lanceolate leaves, bright green, opposite along stems often tinged with red or brown. The tubular bilabiate flowers, with generally lighter and striped throats, are arranged in loose terminal clusters and open in a staggered manner over a long summer period.
In cultivation, they require well-drained soil, sunny exposure, and winter protection in cold regions. Hardiness varies according to the cultivars and is often the primary criterion of choice in the garden.