Rhododendron Photos, Facts, and Care Tips
May is rhododendron month where I live. The flower buds on the rhododendron bushes open, producing beautiful, showy blossoms and a gorgeous display of color. This is a wonderful time of year for gardeners, photographers and everyone else who loves rhododendrons.
The word "rhododendron" comes from two Ancient Greek words - "rhodon", which means rose, and "dendron"' which means tree. Despite the derivation of their name, most rhododendrons grow as shrubs, which are evergreen or deciduous. Some are wild plants, but there are many cultivated forms. These are popular with gardeners and landscapers because of their large and very attractive flowers.
I live in southwestern British Columbia, where the climate is perfect for cultivated rhododendrons. They grow well and abundantly here. They are evergreen plants with large leaves and spectacular flowers that open in late spring. My city has an annual rhododendron festival in May, where people celebrate rhododendron flowers as well as horticulture, nature and the arts.
What is a Rhododendron?
All rhododendrons belong to the genus Rhododendron. The genus is the first part of the scientific name of a living thing. There is a huge variety of plants within the Rhododendron genus, however, and in addition the different varieties easily hybridize, which can make classification difficult. Plant breeders frequently create new hybrids to produce rhododendrons with interesting characteristics. Cultivated rhododendrons are generally identifiied by descriptive names such as Pink Pearl, Saffron Queen and Paprika Spiced.
Ornamental rhododendrons such as the ones shown in most of my photos have large, oval leaves with a glossy dark or medium green upper surface and a dull, pale green lower surface. The flowers are bell-shaped and are born in clusters known as trusses. They may be white, yellow, pink, red or purple In color.
What is an Azalea?
It may seem strange referring to azaleas in an article about rhododendrons, but azaleas are actually a type of rhododendron. The genus Rhododendron is divided into eight subgroups, or subgenera. Azaleas belong to two of these subgenera.
Azaleas are attractive flowering shrubs, but their flowers aren't as large or as showy as those of the ornamental rhododendrons that are so popular in my part of the world. Azaleas also have smaller leaves and are shorter in height. Ornamental rhododendrons can become very large plants and may reach the size of a tree. Most azaleas are deciduous while most ornamental rhododendrons are evergreen.
Another way of distinguishing the two plants is to look closely at the flowers. Azalea flowers tend to be more funnel-shaped than ornamental rhododendron flowers. In addition, an azalea flower has five stamens (the male reproductive structures) while an ornamental rhododendron has ten or more. The stamens produce the pollen grains. They surround the style, which is longer than the stamens and is part of the female reproductive structure.
Rhododendron macrophyllum grows in the Pacific Northwest region of North America. This region is usually defined as the province of British Columbia in Canada and the states of Washington and Oregon in the United States. The common name of Rhododendron macrophyllum is the Pacific, Western or Coast Rhododendron. The plant generally has pink flowers and is the state flower of Washington.
Rhododendron arboreum is the national flower of Nepal. It's known as laligurans or gurans in that country and forms magnificent mountain forests. At lower elevations the flowers are bright red. They change to pink or white as the elevation increases. The plant is also found in India, Sri Lanka, China, Thailand, Bhutan and Myanmar.
Rhododendrons and Other Flowers in Nepal
Rhododendron Care Tips
Grooming and Pruning Rhododendrons
How to Grow Rhododendrons
Most varieties of cultivated rhododendrons require moist but well drained soil that is also slightly acidic. The soil should contain organic matter in the form of peat or compost. It should also be loose, crumbly and well aerated. Rhododendrons require a good supply of water, but the soil mustn't be water-logged. Standing water can cause root rot.
Rhododendrons like a semi-shaded area with dappled sunlight, but will grow in an open area if the sun is not too hot and the soil is sufficiently moist.
Rhododendrons are generally bought from plant stores or nurseries in pots. They have fine roots. The soil around the roots needs to be loosened when a plant is taken out of a pot to be planted. This stimulates the growth of new roots.
Once a rhododendron is growing successfully it may need attention to keep it healthy and compact. Removing dead trusses, or dead heading, not only makes the plant look more attractive but stops it from producing large amounts of seed. This allows its energy to be used for other purposes and may increase its growth. Pruning can help the plant maintain a desirable shape.
How to Plant a Rhododendron
The chief poison in rhododendrons is a type of grayanotoxin known as andromedotoxin. This poison is quite similar in structure to pinene, a component of turpentine.
Andromedotoxin is present in the leaves and flowers of a rhododendron plant. It burns the mouth of an animal or human that eats it, which limits its danger. Most animals avoid it. In addition, our body can break the toxin down. The toxin is harmful if a large amount is ingested, however. It causes stomach upset, nausea and vomiting at first. Soon a low blood pressure develops, as well as muscle weakness and a lack of muscle coordination. The historical record shows that some people have died after eating honey made by bees that have collected pollen and nectar from rhododendron flowers.
At the moment it's hard to go for a walk in my neighbourhood without seeing rhododendron flowers in someone else's garden. I find rhododendrons in multiple colors as well as orange azaleas. Many landscaped areas, parks and botanical gardens also have rhododendrons or azaleas for me to admire and photograph.
Plant stores and nurseries often have a wide selection of rhododendrons that can be purchased. They may also provide information about the plants and offer useful workshops. In addition, there are many rhododendron societies that provide information and growing instructions. Most of these societies have very helpful websites. It's easy for a rhododendron enthusiast to find help!