As the snow finally melts away, fall-planted bulbs and spring ephemerals breathe new life into the outdoors, ushering in the fresh spring air. Alongside their gentle presence emerges one of the greatest flowering displays of the year, a magnificent show of color put on by Azalea and Rhododendron shrubs.
Azalea (uh-ZAY-lee-uh), in the heather family, Ericaceae, also of the genus Rhododendron, are highly hybridized spring-blooming deciduous shrubs, originally native to parts of Asia, Europe, and North America, and growing to four to five feet round. Flowering from early spring to late spring, Azalea produce abundant tubular blooms with five bright petals fused near the center. Azalea are slower-growing shrubs, preferring full or part sun with some shade tolerance, performing best with morning sun and afternoon shade in warmer areas, and requiring moist well-drained acidic soils below pH 5.5 to thrive. While no major pruning is necessary, light pruning to remove dead or diseased wood and to promote bushier growth if desired should be performed immediately after flowering, as Azalea bloom on old wood (the previous year’s growth), and later pruning risks affecting next season’s blooms. Fertilize in early spring and mid-summer with an acid fertilizer to promote healthy blooms for next season. The most successful Azalea for our climate are of the ‘Northern Lights’ series developed right here at the University of Minnesota, available in many colors including ‘Candy Lights’ with fragrant pink flowers and ‘Mandarin Lights’ with bright orange flowers.
Rhododendron (rho-doh-DEN-dron) are highly hybridized spring blooming evergreen shrubs, native to similar regions as Azalea and slightly larger, reaching 4-6' tall and 4-8' wide. Care of Rhododendron is very similar to that of Azalea, though Rhododendron generally prefer cooler, shadier areas. Rhododendron generally bloom slightly later than Azalea as well, flowering from mid-spring to early summer, with larger flower clusters (trusses) of up to twelve flowers in many colors including the incredibly popular bright pink flowers of ‘P.J.M.’ and dark red flowers of ‘Henry’s Red.’