4. Rhododendron L. (rhododendron, azalea)
species, North America, Europe, Asia, south to New Guinea, Australia.
of Rhododendron are cultivated as ornamentals and many cultivars and
hybrids have been developed. The group now informally called azaleas (once
treated as the separate genus Azalea L.) tend to be species that have
deciduous foliage, have mostly 5 stamens, and have funnelform corollas, whereas
rhododendrons tend to have evergreen leaves, 10 stamens, and more bell-shaped
flowers. Our native Missouri species, which is not often cultivated as it
apparently is finicky about soils, is a typical azalea. As a group,
rhododendrons are known to produce poisonous diterpenes and therefore should
not be ingested.