At first glance, rhododendrons and azaleas seem to be nearly the same plant. Classified into the same genus, Rhododendron, and with very similar flowering and growing habits, it's easy to say that it was some sort of confusion between common name and scientific name when discussing the same plant.
In reality though, they are completely different species. Rhododendrons (common name) are those that remain evergreen into the winter with bell-shaped flowers. Azaleas, in contrast, are deciduous - losing their leaves in the winter - with funnel shaped flowers. Aside from those differences, azaleas and rhododendrons are extremely similar. Both prefer well drained soils with an acidic pH between 5 and 5.5. Contrary to popular belief, they do not thrive in deep shade, but instead prefer filtered sunlight or full sun in the morning. Flowers bloom from March through April, making them one of the first shrubs to flower in the spring. Azaleas are more adapted to drier conditions, and are able to tolerate more sun than rhododendrons. Depending on the cultivar, azaleas and rhododendrons are capable of thriving in zone 4 to zone 9. Come winter, the azaleas are more tolerant of colder conditions than rhododendrons, especially in climates where it tends to dip into freezing temperatures with wind. In deciding which cultivar to choose, consider what colors you wish to have in your garden in the early spring. Klondyke Azalea bursts with bright yellow blooms, and will mature to 6-8 feet tall and wide, and is best grown in zones 5-8.
Bloom-A-Thon Lavender Azalea
For something with a longer bloom period, consider Bloom-A-Thon Lavender Azalea. It blooms in March and April, then again in the summer for 12-16 weeks up until frost, and is covered with beautiful lavender flowers.
P.J.M Rhododendron is a standby favorite of many gardeners; the pink flowers engulf the shrub in the spring, and the evergreen nature provides some character into the winter months. They are also one of the most hardy rhododendrons, thriving in zones 4-9.
Autumn Coral Encore Azalea Tree takes the familiar shrub and converts it into a tree form, ideal for a focal point in any garden. The delicate pink flowers cover the shrub in the spring, drawing immediate attention to it. Even when it is not covered in flowers, it makes a statement as a tree form, and is a stunning beauty, regardless of season.
Autumn Sunset Encore Azalea
Autumn Sunset Encore Azalea shrub blooms with orange flowers in the spring, and continues on into the later seasons. Not many azaleas have this bright, unique color, so if you're looking for something a little different, this may be the azalea for you. Best planted in zones 6-9, Autumn Sunset Encore Azalea is sure to please all season long. Regardless of whether you choose to plant an azalea or a rhododendron, the bright spring colors that last into the summer are sure to please and dazzle. With well-drained, acidic soil, your Rhododendron species will thrive and bring you cheerful color wherever you need it.