The Rhododendrons Flower

Rhododendron is a genus of more than 1,000 shrubs and small trees from the heath family, most with large, attention getting flowers.

Scientific Name

The word rhododendron comes from the ancient Greek rhódon, meaning 'rose', and déndron, meaning 'tree'.

Geographic Origin

The rhododendron is native to many areas throughout the world, usually occurring in moist places in the Northern Hemisphere. Rhododendrons are not native to Africa or South America.

Tropical rhododendrons occur in southeast Asia and the north of Australia. There are 55 known rhododendron species in Borneo and 164 rhododendron species occurring in New Guinea. Europe and North America have fewer native species.

Admired for their beauty, rhododendrons are popular throughout the world. Rhododendron catawbiense, is the state flower of West Virginia. This flower also appears on the West Virginia state flag.

Rhododendron macrophyllum, or coast rhododendron, is the state flower of Washington. Other rhododendron species are state flowers in India and Pakistan, and the national flower of Nepal.

Rhododendron Maximum Roseum, or the Rosebay Rhododendron, also called the Great Laurel or Great Rhododendron, is a small tree or large shrub with many trunks. It is commonly found growing in the mountainous areas of North Carolina.

Description and Characteristics

'P.J.M.' rhododendrons are the result of crosses between R. carolinianum and R. dauricum var. sempervirens. The P.J.M. Rhododendrons are small, reaching heights of only 3 to 6 feet.

With a round form and dark green leaves, it is very attractive, especially when the foliage turns almost purplish in color in the autumn. The P.J.M. Rhododendrons are heavy flowerers because they never set seed.

Rho¬dodendron schlippenbachii, or royal azalea, produces very large and fragrant pink blooms in the spring. The foliage on this large leaved azalea also will turn purple in the springtime, velvety green in summer, and then finally will fade to a pretty yellow in autumn.

These beautiful changes in color will occur if the plant is grown in ample sun and moist soil.

Superior Rhododendron Caucasicum, also called the Georgian Snow Rose, is a beautiful shrub originating in the Caucasian Mountains of Russia. This species of rhododendron actually possesses a compound with antioxidant and fat control properties.

Meaning

The noted naturalist, Sir David Attenborough, has brought attention to Rhododendron ponticum, a species of plant that is quite invasive and destructive to other plants. It has also been found that the rhododendron ponticum species contains toxins, even in honey made from its flowers.

This is not completely unheard of, as many other rhododendron species contain toxins, which are not fatal to humans, but which are thought to harm the growth of other nearby plants.

Belladonna meaning “beautiful lady,” is a designation that lets us know this is a poisonous plant. Both amaryllis belladonna and hippeastrum are poiAlthough rhododendrons are hardy and easy to care for, there are several problems to watch for.

Cultivation and Care

Caring for rhododendrons is not difficult, once you are familiar with the plant's specific needs. For one thing, rhododendrons thrive in acidic soil, with a pH from 4.5 to 6.0. Rhododendrons have fibrous type roots, therefore, they require well-drained soil which has a high concentration of organic material.

It is important to become familiar with the needs of rhododendrons if you want to include them in your landscaping. Mulching is very important, as is watering carefully. This is even more important when the plant is not yet established.

Sun and shade requirements will vary with each type of rhododendron. Some like partial shade, but be aware that not enough light will cause them to not bloom.

Diseases and Pests

Rhododendrons can be susceptible to several diseases, including borer damage, major root rot, chlorosis, winter burn, leaf spot, and a twig and stem dieback due to a fungus. It is also easy for rhododendrons to be suffocated by nearby invasive plants.

Chlorosis

Chlorosis is a rather common rhododendron problem. It is a deficiency in iron, and causes the leaves to turn a sickly yellow. Chlorosis is treated by spraying the leaves with a chelated iron fertilizing product, and also by applying it to the soil near the plant.

The pH in the soil must be lowered, to make it more acidic, by adding sulfur or iron sulfate and working it into the soil near the roots. An acidic pH can be maintained, to keep rhododendrons healthy, by using a fertilizer product that is especially geared toward plants that prefer acidic soil.

Winter Burn

If you notice a rhododendron plant looking dry and the leaves turning brown, it is suffering from winter burn, which is exposure to the cold winter air. Sometimes, the plant's leaves will roll up, as it is trying to avoid the drying air of winter, which dries out the leaves faster than the plant can replace them.

Avoid this problem by planting rhododendrons behind other plants or structures that will act as a windscreen. Also, be certain the plants are well watered and mulched before the winter season begins.

Dieback

Rhododendrons are commonly affected by dieback, exhibited by the branches or leaves turning brown, while staying attached to the plant. The leaves may roll up or have spots. Dieback is caused by several fungi, which enter a weakened area of the plant through either infected soil or tools, or rain. Dieback can be treated by cutting away the branches a few inches below the distressed areas.

The affected branches must then be taken away and destroyed, so as not to re-infect the plant. Spray the shrub with a fungicide containing copper sulfate after blooming occurs, and repeat twice more, at 14 day intervals.

Rhododendrons can also become the target of several insect pests, including several different types of weevils, rhododendron borers, and several species of caterpillars.

Spider Mites

Spider mites suck sap from the buds and the undersides of the leaves. This will leave a stippling of yellow or bronze on the leaves. To check for spider mites, hold a white piece of paper under an affected branch and tap the plant. Several tiny insects will drop down onto the paper which will make them much more visible.

Lacebugs

Lacebugs are tiny insects, about a 1/8" with clear lace-like wings. In spring or summer, lacebugs will attack rhododendrons, especially those growing in sunnier, rather than shady spots. They suck sap from the undersides of the leaves, and leave hard, shiny black droppings. The leaves will appear mottled with yellow or green.

Black Vine Weevil

The black vine weevil will also do damage to rhododendrons. The adult black vine weevil causes a c-shaped notch in the leaves by feeding on the plant. Although the notched leaves are not attractive, the weevils usually do not cause severe damage to the plant. Most insect problems can be cured with various insecticides, which can be found at a local nursery.

Deer

Deer will do immense damage to rhododendrons, especially when the plants are smaller. Once the rhododendrons grow larger, and become more 'woody', deer generally leave them alone, but only if they find enough other things to eat. Deer also seem to avoid rhododendrons with heavy fuzz, or 'indumentum' on the undersides of their leaves.

If deer become a problem to the rhododendrons in your area, you will need to either install fencing or put a deer repellent on rhododendrons to protect them. Deer will eat the plants until there is nothing left to save. Deer repellent products can be found at your local garden center. It is best to rotate the use of these products, to ensure that the deer never get too familiar with any of them.

Pruning Rhododendron

Rhododendron pruning is usually not needed on most plants, but some plants may need it to retain shape. The best time for pruning is in early spring, before flowers appear. By pruning at this time, the growth cycle of the plant will not be disturbed. It is essential to prune back every flower terminal.

Any flower terminals not pruned will begin growth a bit earlier than the other blooms, and usually do so by growing a long single shoot. If a single shoot is noticed, it should be pinched off when new growing tips reach about an inch in length. Pinching will encourage multiple branches from the one terminal. This is a crucial step to take when trying to shape or reshape a plant.

Cutting back will make for a future sturdy rhododendron shrub. If pruning back in this manner is done before the plant reaches three feet in height, the need for pruning can be eliminated.

Dead Heading

The rhododendron flower is very beautiful, when it is still a fresh bloom. When a shrub is covered with dried up and dying blooms, it looks unsightly. Dead heading is the removal of spent blooms from a rhododendron bush.

This is done for several reasons: to keep the plant tidy, prevent the production of seeds, which will save the plant's energy for producing flowers for the following year, and helping in the reduction of diseases and pests. Deadheading is the simple act of pinching off the stem of the spent flower. The shrub will look more attractive, and maintain a healthier state.

Uses

Rhododendrons come in many varieties, of many different sizes, colors and flower types. They are generally quite hardy, with colorful, large showy flowers, making them an excellent choice for home landscaping, without requiring too much care.

Rhododendrons are beautiful plants, and an excellent choice for attractive landscaping. By familiarizing yourself with just a few of its needs and preferences, you can enjoy the beauty these lovely plants offer.