Rhododendrons and Azaleas (Rhododendron sp.)

With their colourful papery flowers, blooming profusely in the spring against a background of dark green leaves, rhododendrons and azaleas worked well against the reds and greys of New Haven. Technically, both rhododendrons and azaleas fall under the Rhododendron genus, except that the former, or so called ‘true rhododendrons’ have ten stamens per flower, and the latter only five. (I always remembered it as the one with more letters in the name also having more stamens). The genus consists of a whopping 1024 species (a kilobyte! ..Sorry), and is found mainly in Asia, as well as in the southern highlands of the Appalachian range in North America. Although rhododendrons can be either deciduous (sheds leaves in the winter) or evergreen, the ones they planted in New Haven tended to be evergreen, quite impressive considering how harsh some of the winters could be. The name itself is derived from the Greek words for rose (rhodos) and tree (dendron).

azaleas yale

Red azaleas in New Haven

Rhododendrons and azaleas have very distinct characteristics. Although they’re mostly shrubs, they can occasionally grow to be trees. Leaves grow in spirals, often with a cluster of flowers in the centre of the whorl, although many azaleas bloom singly. Flowers have five petals, delicate and often marked with dots or splashes of colour that help guide insects to their nectar. Stamens are long, curved upwards and protrude out of the flower, and have clumped pollen. In general, both the leaves and flowers or rhododendrons are larger than that of azaleas.

Rhododendron tend to like being planted in dappled shade, where they get just a little sun each day. They need well-drained soil to prevent waterlogged roots, and ideally moist soil or mulch at a pH of 4.5 to 5.5. If the roots dry out, leaves will curl and twist to indicate their sad state. They like being well-nourished with organic fertilizers or humus (decaying material), and have shallow root systems, so don’t plant them too deep.

Interestingly, despite their beauty and popularity as a landscaping plant, as well as Rhododendron arboretum (known locally as Lali Gurans) being the national flower of Nepal, rhododendrons and azaleas have quite the bad rap to their name. In Victorian flower symbolism, they mean danger, and to beware. A bouquet of flowers in a black vase signified a death threat. In Nepal though, it’s often seen as an offering in temples. In Chinese culture, azaleas are known as 思乡树, or ‘tree that evokes a longing for one’s hometown’. The reason for this is rather poetic indeed- the branches and leaves of the azalea are always inclined towards the same direction, regardless of harsh winds and rains, implying that one’s heart always belongs to one’s hometown, wherever he or she goes.

Part of the reason why azaleas in particular have rather sinister symbolisms is that azaleas and some rhododendrons are very toxic, containing grayanotoxins in their leaves and nectar, which act on channels for sodium ions in cells. Although they don’t necessarily kill humans, they can cause excessive salivation, dizziness and vomiting at low doses, and muscle weakness, paralysis, breathing difficulties and cardiac (heart) problems at higher doses. Honey produced from certain species of Rhododendron, known quite literally as ‘mad honey’, can also cause delirium and hallucinations, something that the Gurung people of Nepal and ancient Roman troops made use of. Lali Guran (Rhododendron arboretum) flowers are eaten in Nepal, sometimes pickled, made into a juice or squash, and added to curries to help soften bones. In traditional medicine, it is believed that the powdered flowers mixed with rice can help treat dysentery, the bark is used to cure coughs and diarrhoea, and herbal teas made with the flower are thought to improve digestion and help with stress and lung disorders.

Back in New Haven I had no interest in nibbling at any of the roadside bushes, so I settled with taking photos of every colour of Rhododendron I bumped into instead.

rhododendrons azaleas


  1. http://baike.baidu.com/item/%E6%80%9D%E4%B9%A1%E6%A0%91
  2. http://olgarani.blogspot.sg/2010/10/rhododendron-national-flower-of-nepal.html
  3. http://selections.rockefeller.edu/stopping-to-smell-the-rhododendron/
  4. http://www.almanac.com/plant/rhododendrons
  5. https://en.wikipedia.org/wiki/Azalea
  6. https://en.wikipedia.org/wiki/Grayanotoxin#cite_note-15
  7. https://en.wikipedia.org/wiki/Rhododendron
  8. https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/rhododendron-care.htm

2 thoughts on “Rhododendrons and Azaleas (Rhododendron sp.)

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