Propagation
Surface-sow fresh seeds in boxes using a sandy-peat media that is lime free and cover them lightly with sphagnum or sand. Keep moist and pot up as soon as large enough to handle.

Take semi hardwood cuttings that are 25 mm (1 in) to 200 mm (7¾ in) long from early to late summer. All but the top leaves should be removed and they can be reduced by half to improve aeration and reduce evapotranspiration. 

Prepare the base of the cutting by removing a slither of bark up to 25 mm (1 in) long then dip the end in to hormone rooting powder that contains indolebutyric acid. 

Place the cuttings in a well-drained media and maintain a temperature of 21° C (70° F) and apply water misting on a regular basis. Take care not to over water as this will promote fungal attack.  Cuttings should root up within 6-weeks or may take up to 12 months for some species.  

Cultivars may be grafted onto a rootstock.
Aerial or ground layering it is carried out during the growing period.

Botanic information
Leaf: The leaves vary but generally they are ovate-oblong with an acute to acuminate apex and a short petiole. The texture is leathery and the colour is normally dark green.

Flower: The funnelform to campanulate flowers have 5-petals and 10-stamens. There is a wide colour range from white to pink and shades of yellow. Several flowers are arranged in a loose terminal umbel (Truss) and appear during spring.

Fruit: The small woody capsule is commonly accompanied by the persistent calyx and contains numerous tiny seeds with thread like tails to aid in wind dispersal. The small seeds are viable but the plant is commonly reproduced vegetatively to maintain true to type.

Culture
Rhododendrons grow best in a sandy loam that is tending acidic and is well drained with a mixture of leaf mould and peat that is kept moist, and friable. They do not thrive in clay or limestone based soils with a high pH and is very sensitive to salinity. 
These shrubs require protection from strong winds due to the shallow root system and dislike hot afternoon sun, preferring a semi-shaded position.  

As they are shallow rooted they are easily transplanted with a good ball of soil kept around the roots. When replanting apply a thick layer of mulch which will retain the soil moisture, improve soil aeration and decrease the penetration of frosts in cold areas.

When planting from a container you may make vertical slits down the root ball with a sharp knife to ensure contact with the new soil and the hole once planted it should not be allowed to dry out. 

The large leaf forms tolerate a shaded position, under deciduous trees or on the southern side of buildings and the smaller azaleas can tolerate a sunny position, but all forms require adequate light for flowering.  

Normally little pruning is required, but rhododendrons will tolerate cutting back if they become leggy or to rejuvenate.