Rhododendrons and azaleas are arguably the South’s favorite shrubs. Many people think of them as entirely different plants, but they both belong to the genus Rhododendron, which comprises more than 800 species and 10,000 named selections.

Even to the untrained eye, one difference between the two groups is obvious: rhododendrons generally have much larger leaves. From a technical standpoint, rhododendron flowers are bell shaped and have ten or more stamens, while azalea blooms are typically funnel shaped and have five stamens.

By making their choices carefully, gardeners in almost every part of the South can enjoy some of these plants, even if that means growing them in containers. Rhododendrons generally do better in the Upper and Middle South, though a number of selections thrive in the Lower South.

Azaleas, however, are more accommodating; with the necessary attention to soil, light, and proper selection, they can be grown throughout the South.

Source