Rhododendron subg. Hymenanthes is a subgenus of the genus Rhododendron

Rhododendron

Rhododendron is a genus of over 1 000 species of woody plants in the heath family, most with showy flowers...

, with a widespread distribution in the temperate Northern Hemisphere

Northern Hemisphere

The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

. The species are evergreen

Evergreen

In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...

 shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s and small to medium-sized tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s (up to 20 m tall), with medium-sized to large leaves (very large, over 40 cm long, in a few species). The flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s are large, produced in terminal trusses of 5-40 together.

The subgenus includes one section, R. sect. Ponticum, divided into 24 subsections and about 140 species:

• R. subsect. Arborea (three species)
• R. subsect. Argyrophylla (six species)
• R. subsect. Auriculata (one species, R. auriculatum)
• R. subsect. Barbata (two species)
• R. subsect. Campanulata (two species)
• R. subsect. Campylocarpa (four species)
• R. subsect. Falconera (seven species)
• R. subsect. Fortunea (ten species)
• R. subsect. Fulgensia (two species)
• R. subsect. Fulva (two species)
• R. subsect. Glischra (five species)
• R. subsect. Grandia (nine species)
• R. subsect. Griersoniana (one species, R. griersonianum)
• R. subsect. Irrorata (seven species)
• R. subsect. Lanata (one species, R. lanatum)
• R. subsect. Maculifera (six species)
• R. subsect. Neriiflora (19 species)
• R. subsect. Parishia (three species)
• R. subsect. Pontica (13 species)
• R. subsect. Selensia (five species)
• R. subsect. Taliensia (20 species)
• R. subsect. Thomsonia (seven species)
• R. subsect. Venatora (one species, R. venator)
• R. subsect. Williamsiana (one species, R. williamsianum)

Cultivation

This subgenus includes the majority of the larger evergreen rhododendrons widely grown as ornamental plant

Ornamental plant

Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

s. Some species, notably Rhododendron ponticum

Rhododendron ponticum

Rhododendron ponticum, called Common Rhododendron or Pontic Rhododendron, is a species of Rhododendron native to southern Europe and southwest Asia.-Description:...

, have escaped from cultivation and become invasive

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 in some regions such as New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

.