Penstemon, also known as beard tongue, is native to North America and East Asia, but it is suited to the UK's climate. The flowering plant grows from 90 cm to 1.5 m (3 to 5 feet) tall and produces bell-shaped flowers in shades of red, pink, white and purple. Grown as an ornamental, the flowers attract butterflies and birds to the garden. Propagate penstemons from cuttings taken in early spring or late summer, before the plant blooms or after the blooms are spent.
Take 15 to 20 cm (6 to 8 inch) cuttings from the stem tips of the penstemon plant, using the pruning shears or a sharp knife. Remove the lower leaves from the cuttings and trim the remaining leaves to half their original size. Keep the cuttings in water until you plant them.
Fill a container with a mixture made of one half sand and one half peat moss. Moisten the mixture and smooth the surface. Make several holes for the cuttings, at least 7.5 cm (3 inches) deep.
Pour 1 tbsp of powdered rooting hormone onto a paper plate and dip the exposed end of the cutting into the powder. Gently shake off the excess and stick the penstemon cuttings into the holes of the soil. Tamp down the soil with your fingers to keep the cuttings upright.
Cover the cuttings with a clear plastic bag or clear cling film. Seal the plastic around the container to create a miniature greenhouse. Make one or two slits in the bag for ventilation.
Place the cuttings in a bright location but out of direct sunlight. Check the cuttings daily to remove any stems that die or become diseased. Keep the soil slightly moist during the rooting process.
Check the penstemon cuttings, after four weeks, for root growth. Gently tug on the leaves and feel for resistance. The slightest resistance means the cuttings are developing a root system. Remove the plastic when the roots develop.
Transplant the new plants into separate containers or directly into the ground, if weather permits. It is best to allow the plants to overwinter indoors or in a protected area before planting them in the garden.
Keep the plastic from touching the cuttings so leaf rot does not develop. Insert skewers or small sticks to keep the bag off the cuttings.