For a surprising pop of color, walk through the Missouri Botanical Garden between the second week of April and the second week of May to see clustered bursts of color from the dazzling spring shrubs of the Genus Rhododendron.
The understory fireworks of spring, rhododendrons and azaleas are closely related shrub species in the heath family, Family Ericaceae.
The Garden displays over 2000 specimens of rhododendrons, encompassing 44 species and a wide sampling of hybrid cultivars. While distributed throughout the Garden, the most concentrated collection of rhododendrons is planted in the Rhododendron Garden map (pdf), located at the western side of the Ridgway entrance into the grounds.
In the Lopata Azalea-Rhododendron Garden, the beds hug the rise and fall of the landscape. And from these gentle mounds erupt rhododendrons and azaleas, large and small, evergreen and deciduous. Since the late 1970’s, this approximately one acre garden has been full of spring color, supplied by over 950 individual shrubs, as the growing season commences. There are 15 species represented in the Rhododendron garden, including two deciduous azaleas that are native to the US: the pinxterbloom (Rhododendron periclymenoides) and the roseshell (Rhododendron prinophyllum). Both produce trumpeting bouquets of pink blossoms in late April through early May, with the roseshell often being fragrant. The Korean azalea (Rhododendron yedoense var. poukhanense) flaunts its open-faced lilac blossoms throughout April.
Standout hybrids in the Rhododendron garden include evergreen rhododendrons of the PJM Group, which can bloom as early as March; the evergreen azaleas 'Delaware Valley White' and 'Yaku Prince', the latter which produces flowers that have a gradient of color between pink and white; and a low-growing evergreen azalea, ‘Pink Pancake’, which can be used as a ground cover and flowers into June.
Rhododendrons and azaleas are numerous in the Japanese Garden (448 specimens), both around the lake and on the islands, including the evergreens 'Girard's Crimson' and 'Hino-crimson' (visit in the last week of April to see these). The Woodland Garden (>300 Rhododendron specimens, covering 13 different species) represents a more natural habitat for a rhododendron or azalea, as shrubs in the acidic and organic soils of a forest. Look for the pink-touched, cream-colored flowers of 'Mary Fleming' (early April) or the fragrant and flashy pink petals of ‘Rosy Lights’.
Two rhododendron hybrids have been selected as Plants of Merit. On display at the Kemper Center, the deciduous azalea 'My Mary' produces yellow, citrus-scented blooms during the last week of April and the first weeks of May. The evergreen azalea 'Girard's Rose', which sends forth ruffled magenta flowers through April and early May, is on display in both the Rhododendron garden and the Japanese Garden.