Guide to Rhododendrons

Rhododendrons are acid-loving plants which produce spectacular clusters of large, showy and often fragrant flowers. They originate from the Himalayas (where the rhododendron is the national flower of Nepal) and have long been a mainstay of the woodland garden since being introduced into Britain by Victorian plant hunters. Rhododendrons typically grow best in partial or dappled shade, although azaleas are much more tolerant of full sun and in fact dwarf alpine varieties actively prefer it. They look best when grown in groupings to create block colours or loose drifts and combine well with evergreens such as Pieris 'Forest Flame' and Euphorbia 'Tasmanian Tiger'.We recommend choosing an overarching scheme of around 3 colours if you have a larger area to plant up.

What's the difference between a rhododendron and azalea?

Rhododendrons and Azaleas are both from the Rhododendron family. Rhododendron is a genus (group) of plants with common characteristics, whilst azaleas are a sub-group within this genus, rather than being a genus of their own. There is no definitive way of distinguishing all azaleas from all rhododendrons but each has its own qualities and characteristics which are important to understand when choosing the right plant for your garden.

• Evergreen vs. Deciduous. Rhododendrons are evergreen whilst azaleas are deciduous. The exception is Japanese azaleas which are evergreen (making them popular at Christmas).

• Growth Habit. Azaleas are small to medium sized shrubs with many, smaller stems whilst rhododendrons tend to be larger plants with fewer stout stems. Rhododendrons have larger flowers and foliage, except for dwarf varieties which are <1 metre tall and suitable for the rock garden.

• Foliage. Rhododendrons have big, oval, leathery leaves. Azaleas have smaller, narrower, sometimes hairy foliage which takes on brilliant hues of yellow, orange and crimson before falling to the ground in autumn (except for Japanese azaleas). Japanese evergreen azaleas actually produce 2 sets of foliage each season: a first in the spring followed by a second in the summer.

• Flowers. Rhododendrons produce large bell-shaped flowers in clusters. They are available in a range of colours spanning reds, yellows, pinks, purples and even white. Rhododendron flowers have been used for some time to make popular fruit and flower wines. In contrast, azaleas blooms are smaller and either tubular or funnel-shaped. Both mainly flower in spring but with a growing range of summer flowering varieties now on offer to add charm and beauty to your garden later in the year, with "encore azaleas" blooming in early spring then again through the summer.

• Growing Conditions. Rhododendrons are quite fussy, requiring partial or dappled shade (except for alpine varieties which prefer full sun) in a sheltered spot in an acidic, moist yet free-draining, humus-rich soil. Azaleas are generally more adaptable, although a moist, acidic soil is still a 'must have'. Japanese azaleas are again the exception, being more sensitive of cold winters than both deciduous azaleas and rhododendrons.

Choosing a rhododendron or azalea

There are a huge range of rhododendrons with over 900 varieties spanning low growing ground cover plants to specimens that can reach 6 metres tall. Larger varieties make great hedges, screens and foundation plants whilst dwarf alpines are highly effective in rock gardens and compact hybrids look excellent in containers positioned in a shade spot of the garden. We've summarised some of the best rhododendrons with different eventual heights below:

Dwarf (<1 metre tall)

Rhododendron 'Axel Olsen'

Rhododendron 'Baden Baden'

Rhododendron 'Curlew'

Rhododendron 'Drake’s Mountain'

Rhododendron 'St. Merryn'

Rhododendron 'Wee Bee'

Rhododendron azalea japonica 'Blue Danube'

Rhododendron azalea japonica 'Diamond White'

Rhododendron azalea japonica 'Explorer'

Rhododendron azalea japonica 'Geisha Orange'

Rhododendron azalea japonica 'Mother's Day'

Rhododendron impeditum 'Select'

Rhododendron williamsianum 'Karin'

Rhododendron williamsianum 'Linda'

Rhododendron yakushimanum 'Dopey'

Rhododendron yakushimanum 'Dreamland'

Rhododendron yakushimanum 'Dusty Miller'

Rhododendron yakushimanum 'Golden Wedding'

Rhododendron yakushimanum 'Polaris'

Rhododendron yakushimanum 'Sneezy'

Rhododendron yakushimanum 'Surrey Heath'

Small-Medium sized (1-2 metres tall)

Rhododendron 'Blue Diamond'

Rhododendron 'Praecox'

Rhododendron 'Scarlet Wonder'

Rhododendron azalea 'Gibraltar'

Rhododendron azalea 'Homebush'

Rhododendron azalea 'Persil'

Rhododendron azalea japonica 'Palestrina'

Rhododendron x hybrid 'Anna Rose Whitney'

Rhododendron x hybrid 'Bernstein'

Rhododendron x hybrid 'Goldflimmer'

Rhododendron x hybrid 'Horizon Monarch'

Rhododendron x hybrid 'Lees Dark Purple'

Rhododendron x hybrid 'Lord Roberts'

Rhododendron x hybrid 'Tortoiseshell Orange'

Rhododendron yakushimanum 'Bashful'

Rhododendron yakushimanum 'Fantastica'

Rhododendron yakushimanum 'Golden Torch'

Medium Sized (2-3 metres tall)

Rhododendron 'Gomer Waterer'

Rhododendron azalea 'Berryrose'

Rhododendron azalea 'Fireball'

Rhododendron azalea 'Golden Eagle'

Rhododendron azalea 'Satan'

Rhododendron yakushimanum 'Percy Wiseman'

Large (>3 metres tall)

Rhododendron azelea 'Luteum'

You may also be interested in our other articles on How to plant, grow and care for Rhododendrons.