Azalea

Cover photo by Josh Whitener.

#TeachingTuesday: Azalea

This week we are talking about azaleas. There are many different species of azalea, but they all fall under the genus Rhododendron. There are many different species of azalea, but they can be broken down into two main categories: deciduous and evergreen. Deciduous azaleas are mostly native to the US, and many of them can be found growing wild in the mountains of North Carolina. They drop their leaves in winter, and is spring bloom with large but delicate flowers, ranging in color from white and pink to orange and even red.  Evergreen azaleas are the ones more commonly used in landscaping, and they are mainly native to Japan, but some originated in China, Korea, and Taiwan. They keep their leaves year-round, and bloom in mid- to late-spring with fluffy flowers that often completely cover the entire shrub. There are some hybrid azaleas that bloom again in the fall, known as reblooming azaleas. Some of the trademarks these are sold under are Encore® and Bloom-A-Thon®. Evergreen azaleas range in color from white to pink, lavender, and rose, to darker shades of orange, red, and purple.

Cultivation

Both types of azaleas, deciduous and evergreen, bloom on old wood, meaning the flowers appear before the new growth. This means it is very important to wait until after flowering to do any pruning, otherwise you will be removing the next crop of flowers. Pruning should be done selectively, only removing certain branches to improve the shape of the shrub, increase air flow within the interior, or remove disease. Shearing is not recommended.

The most important factor for successful cultivation of azaleas is proper site selection. Azaleas are shallow rooted, so choosing a site with proper soil is critical. Excessive soil moisture will cause root rot, so the soil should be well-drained. Azaleas prefer acidic soils, and will grow well under pine trees. Because of their shallow root systems which can dry out easily, they must be kept watered until they are well-established. They do not grow well under maple, ash, and shallow-rooted oak trees where there is too much competition for water and nutrients. They will not grow well in full sun or intense afternoon sun; morning sun or filtered light throughout the day is best. If they receive too much sunlight, it will stress the plant, and they will be susceptible to infestations of lace bugs. For this reason, do not use azaleas as a foundation plant along the south or west sides of a building.

ID Tips

• Both deciduous and evergreen azaleas have elliptic leaves (like an oval with two pointed ends) with smooth edges.
• The leaves are covered in tiny hairs that may feel soft or like sandpaper.
• Evergreen azaleas have tiny reddish hairs on the twigs and branches.
• Most azalea flowers are made of 5 petals that fuse together at the base to form a funnel, but there are also some double varieties that have extra petals in the center.

Evergreen Azalea                                                                                 Deciduous Azalea