Rhodendron


(Species: Rhododendron - Family: Ericaceae)

 

Rhododendron and its origins

The word Rhododendron stems from the ancient Greek 'rhodon', meaning rose, and 'dendron', meaning tree. It is a huge group of over 1,000 species, most of which have showy flowers.  They are shrubs that range in size from small rockery-sized to tree-like growth, and can be evergreen, semi-evergreen or deciduous.

 

The plant has been widely hybridised so that there are now over 28,000 cultivars listed by the Royal Horticultural Society. Most are fully hardy. The Rhododendron group includes the smaller azalea, which has one blossom for each stem, as opposed to clusters.

 

Seasonality: Rhododendron in flower

Rhododendron foliage can be deciduous or evergreen, leaves usually oval, in deep green or grey-green, and large or small, waxy or leathery. Flowers, held in racemes, can be bell, saucer or funnel shaped, and are sometimes fragrant.  The colour range is wide, from luscious pastels of peaches, pale pinks and lemons to rich shades of cerise, flame and purple.

 

The flowering period is from mid to late spring, and lasts several weeks. Rhododendrons are frequently used in landscaping as they are large, bloom reliably and are evergreen. In parks and public gardens, a large rhododendron in bloom, appearing to be a dazzling sheet of colour from a distance, is a wonderful sight, but for the average garden, smaller Rhododendrons of about 1.80m -2m, such as Pink Pearl and Purple Splendour, are a more suitable option.

 

R yakushimanum, a dome-shaped evergreen of 1m high and 1.5m spread from Japan, has powder-pink funnel flowers that fade to white in spring, and in recent years has been responsible for many garden-worthy, low-growing hybrids, such as Percy Wiseman, Hydon Hunter and latterly in German Rhododendron breeding programmes, the highly floriferous Fantastica and Rendezvous.

 

How to plant: Rhododendron

At home in the moist, acidic soil of heath and woodland, Rhododendrons and Azaleas thrive in patial shade.  Placing them in around larger shrubs and trees is ideal - and in soil that is well-drained. They must have neutral to acid soil, and will not tolerate lime.

 

Plant shallowly, as Rhododendrons are surface-rooting, adding organic matter to the planting hole and mulch regularly with organic matter or leaf mould.

If feasible, deadhead flowers with finger and thumb to discourage seed production and promote new blooms.

Late winter is the time to cut back leggy Rhododendron stems. 

 

Propagation of Rhododendron

Either take semi-ripe Rhododendron cuttings in late summer, or layer plants between mid-spring and late summer, in which case it might take up to two years for plants to form a substantial root system. 

 

Did you know?

Rhododendrons did not become popular in the United Kingdom until Victorian times.

 

Rhododendron ponticum, introduced to Ireland from the UK, is now considered invasive. The plants form new shoots from their roots and are replacing the understorey of woodland areas, proving near impossible to eradicate.

 

Some species of rhododendrons are toxic to grazing animals and horses can die within a few hours of ingestion. Honey made by bees feeding on Rhododendron and Azalea blooms can make people ill and can even prove fatal.