Rhododendrons (from Ancient Greek "rhodon" – rose and "dendron" – tree) is a genus of plants in the heath family (Ericaceae), deciduous, evergreen or partly evergreen shrubs or even trees.

The Rhododendron genus is distributed mainly in the Northern Hemisphere cold and temperate regions. Most rhododendron species are native to East Asia and Southeast Asia. They are also found in North America and Europe. Most of rhododendron species are spread in mountainous areas, in the vicinity of a large pool of water, the oceans, seas, lakes and rivers. They occur in places with moderate temperatures, high air and soil moisture. Substrate in places, where rhododendrons are native, are acidic (most species grow in areas with pH 4.7), well-drained, with high content of organic matter.

The Rhododendron genus is wide and diverse. Botanists have described 1200–1300 wild species so far. There are species of rhododendron that cover ground growing only a few centimeters high while others grow as shrubs and even trees, reaching 30 m in height. In Latvia rhododendrons grow as shrubs, reaching about 3 m in height. Some species have small leaves, only 1 cm long, but others have leaves that reach up to 60–100 cm in length. There is also a big variety of sizes, shapes and colours of the flower. Flowers of small-leaved and low species are smaller than 1 cm in a diameter. The flower of most species is 4–8 cm in diameter, but there are also species that have flowers with diameter up to 20 cm. The colour of flowers also is very varying: white, pink, red, purple and mixtures of these colours.

This large diversity of genus Rhododendron is the reason why rhododendrons are so popular in the world. Compared to other ornamental plants which people know like crop for several thousand years, rhododendrons started to cultivate in gardens relatively recently – in the 17th century (since 1656). Breeders have grown more than 30000 rhododendron cultivars in these three centuries. Today, the garden architects almost always include rhododendrons in a garden plan because they have a very large choice of options provided by this extreme diversity of genus.

Rhododendrons began to grow in Latvia in the 19th century 20-ies. Today, every gardener in Latvia knows rhododendrons and tries to plant them in a garden.