Plant Profile | Rhododendron
Rhododendrons are beautiful ornamental shrubs that bring a blaze of colour and stunning flowers to the garden in early spring. Most varieties are evergreen and are a great year-round feature even when the days of spring are a distant memory.
Rhododendrons have spectacular flowers that add colour to the garden in early spring before the other plants have come into flower. They are perfect for containers but also work well as a woodland themed border, or as a standalone feature shrub. Their colour and versatility make them a fantastic addition to any garden.
A selection of some of our best-loved varieties of rhododendron to try in your own garden.
Dreamland has dome-shaped pale pink flowers that deepen as the plant matures, leaving it with dark pink edges. It has dark foliage with stiff green leaves that are pale underneath.
The funnelled flowers on Cosmopolitan begin with a deep red flare, and glossy dark leaves, which then gradually fade to a softer shade of light pink.
Rhododendron Cunningham’s White
Cunningham’s White put on a truly stunning display. These robust plants start out with mauve buds that grow into loose trusses of funnel-shaped white flowers.
Type: Most varieties of Rhododendron, particularly the ones in Hillier Garden Centres, are evergreen, however, there are some that are deciduous.
Flowering time: Spring.
Sun Requirements: Partial shade.
Soil: Rhododendrons require acidic soil. If this is not possible, then they also are ideal for container planting with ericaceous compost. They do require good drainage so avoid water-logging by ensuring the container has drainage holes.
Hardiness: Fully hardy.
Eventual size (height x width): This varies drastically depending on the type. Compact varieties can grow up to 1.15m whereas tall hybrids, such as R. Alabatross Townhill, can grow to two metres. Dwarf (alpine) varieties are available, which grow to around 80cm. At the other end of the scale are Woodland Rhododendrons which can reach upwards of 12 metres!
Rhododendron Plant Care
Rhododendrons can be planted from October to March.
Good soil preparation is absolutely vital for rhododendrons and it is definitely worth spending the time to get it right. Prepare an area that is larger, but not deeper, than the root ball to allow for growth. Place the rootball two inches higher than the soil and use a base of organic matter, such as leafmould or bark, and mix this into the soil. When the plant is in the ground, lightly cover it. It is best to avoid compaction so that the air can circulate so be careful not to pack in the soil around it.
When picking the location for your rhododendron be mindful of shade. A spot with dappled shady patches that can provide some shelter is ideal, but they don’t like to be in full shade or too close to dense tree growth which will take the moisture and light away from the plant. Avoid areas that catch the early morning sun if possible.
If you are opting for a rhododendron in a container, remember that the hybrid R.yakushimanum make excellent subjects for container growth. Dreamland is just one of these and is perfect for containers and small gardens. Remember that rhododendrons aren't suitable houseplants, and they should be kept outdoors.
Rhododendrons require frequent watering but find tap water to have too much calcium for them to flourish so rainwater is recommended, particularly in hard water regions.
Rhododendrons are a difficult plant to root. They require a late autumn cutting, to be done in October and this can take three to four months to root. During this time they need to be kept moist to prevent water loss, but not wet as the stem will rot.
Rhododendrons need a 'wound' on the base to assist with root development and a hormone rooting powder. Tips that have started to harden should be used. Softer wood roots more easily, but is more prone to rotting.
It may be best to propagate a single new rhododendron plant using the layering technique. To do this, select a young branch growing low on the plant which can bend down to ground level. Remove side shoots and flowers from the branch and wound the underside of the branch - cutting down to the white wood. Apply hormone rooting powder to the wound and place the branch in a shallow hole in the ground. Peg the branch down and cover it with compost. This branch should be weighed down using stones and watered regularly, within 12 months roots should develop and the branch should be ready to be separated from the parent plant and transplanted.
Rhododendron Planting Ideas
Camellias have the same soil requirements and care conditions as rhododendrons, so make ideal companions. They also grow well with other woodland plants that thrive in shady areas, such as Dicentra spectablis and Iris siberica, which add a beautiful burst of striking colour.
Dwarf varieties look great when sitting in a rock garden, they are slower growers so extend the flowering period into early summer. As well as being compact, dwarves have an incredibly varied range of colours too with greens being complemented by reds, bronzes, blues and even golds.
Rhododendrons grow brilliantly with tulips to make a picturesque spring border early in the season when they bloom. Beyond that, consider complementing their foliage with shrubs that can provide colour throughout the year during the rhododendrons non-blooming months. When selecting other plants stay clear of any that are moisture-hungry so the rhododendrons won’t have to compete.
Rhododendron Expert Tip
Rhododendrons don’t like to be planted too deeply. They are surface rooting so their roots should only just be covered. If planted too deeply, they will struggle to flower.
The nectar of Rhododendron ponticum can be used to create, what has been termed, “mad honey”. Honey made from the nectar has hallucinogenic and poisonous effects so was used in 67 BC by the Persian army as a weapon against the Roman army. It can still be found today, particularly in Turkey where the ponticum originates from.