Canyon penstemon produces 3-foottall spikes of rose-purple flowers in the spring months. These tubular blossoms are just irresistible to hummingbirds. After blooming, you can cut the stalks back to form a tight rosette of foliage. This penstemon species has glossy green serrated leaves. As its name suggests, Canyon penstemon grows wild in canyons and washes across the southwestern U.S. Good drainage is essential for this and most other penstemons.