Rhododendron is the name given to a genus of flowering plants that all belong to the Eriaceae family. This large genus has more than one thousand species in it and almost all of them have spectacular flower displays. Most of the plants belonging to this genus are known as azaleas to many gardeners. Rhododendron is also the national flower of Nepal.

Appearance

This genus is made up mostly of shrubs, small trees, and very rarely, large trees. The smallest tree of this species is a mere one metre tall while the largest can be over thirty metres tall. The leaves of these plants are arranged in spirals and can range in size from one centimetre to fifty depending on the species of the tree. Some trees are evergreen while others are deciduous. The lower surface of the leaves of these plants tends to be covered in hairs or scales. The alpine species have small leaves and small flowers while the more tropical species are larger and grow as epiphytes.

Distribution

Rhododendron is a genus that is very widely distributed as it can be found occurring through most of the northern hemisphere except for extremely dry locations, and also extends into the southern hemisphere and areas such as northern Australasia and south eastern Asia. The highest diversity of these species is found in the Himalayan mountains.

These plants are grown in many commercial areas for sale and are sometimes found in the wild as well, but due to their popularity are becoming less common in the wild. They are used for large scale commercial growing and hobbyist growers also make great use of them. These plants are resistant to rot if they are over-watered and can be forced to develop buds early. They are also very easy to root and propagate, making them popular trees that are bought and sold a lot.

Recent research has shown that these plants have hepatoprotective and anit-inflammatory functions against many diseases due to the antioxidant compounds within them such as saponins, flavonoids and phenol. The root of the plant is thought to regulate kidney function by lessening the activity of a particular compound, NF-κB.

Popularity

Both hybrid and species of these plants are used widely as ornamental plants for landscaping in several different parts of the world. They are valuable in landscaping because of their size, structure, flowers and the fact that most of them are evergreen. They are popular when making foundations and for use as hedges, and many of the larger plants are used in woodland gardens, in informal plantings and as specimen plants.

Care Tips

Similar to other ericaceous plants, most of these plants prefer soil that is slightly acidic, with a pH of around 4.5 to 5.5. The more tropical plants of this genus grow as epiphytes and therefore they need a planting mix that is similar to the ones needed by orchids.

These plants have fibrous roots and thus they prefer soils that are well drained and have plenty of organic material. If the soil is alkaline or poorly drained, the plants tend to grow in raised beds. Watering and mulching are important for these plants, particularly until the plant establishes itself.