How to Prune Rocky Mountain Penstemon

Overview

Native to dry woodlands, this relatively inconspicuous evergreen plant, with glossy narrow leaves, bears 18-inch stalks of deep blue-violet flowers each spring. Its beauty and drought tolerance has made this hardy jewel a classic component of water wise gardens. Like many other Southwestern natives, Rocky Mountain penstemon thrives on lean soils, modest amounts of water and little care. Too much pampering can actually cause weak growth and poor bloom. Proper early pruning will make plants bushier and produce more flowers. Pruning spent flower stalks will give your garden a manicured appearance.

Step 1

Cut or pinch the tips of young plants in spring when the plant is well established, just above the second set of leaves on each stalk to encourage bushiness. Don't cut the bottom rosette of leaves, just the tip ends of new stalks growing out of the base.

Step 2

Trim off the spent flower stalks down to the base of the plant before the seeds ripen in summer to save energy in young Rocky Mountain penstemons. Sometimes this may even trigger a second bloom. You can also wait to trim the stalks until after the tiny black seeds fall away from the dry capsules so the plant can reseed.

Step 3

Prune woody, older stalks from the base of the plant in late autumn to encourage new growth the following spring.