Bring on Spring bling: Ciar Byrne says roll up for the rhody show with a burst of joyful colour

This has been a long, cold winter and I’m ready for some colour and excitement in the garden. Just in time, rhododendrons and azaleas put on their bling spring show in acid pinks, reds and purples.

Rhododendrons are one of the oldest plant species on Earth. They’ve existed for at least 55 million years and are found in the wild in upland habitats across North America, Europe, and Asia.

Azaleas are part of the same family, but are smaller, more sweetly scented and can be deciduous, while rhododendrons are evergreen. Both need soil with a high PH and lots of rain.

Alpine adventure

The first rhododendron to be classified and named was R. hirsutum, the Alpine rose, discovered by the pioneering 16th-century Flemish botanist Charles l’Ecluse in the Alps. In the 18th century, collectors began to bring seeds back to England from North America and, later, from Asia.

In London, the gardens of Kenwood House on Hampstead Heath, designed by Humphry Repton, boast a dazzling display of rhododendrons in spring, beneath Scots pines and mature beech trees. A quarry forms the perfect environment for banks of these glossy evergreens, with highlights including R. ‘Cynthia’, with its deep rose-pink flowers.

Exbury Gardens in the New Forest (exbury.co.uk) is another great spot to find hybrid cultivars of rhododendron bred by the de Rothschild family, blooming from now until May, beginning with pale pink R. ‘Christmas Cheer’.

At Leonardslee in West Sussex (leonardsleegardens.co.uk), the second baronet Sir Edmund Loder was a keen plant collector who gave his name to R. loderi, which is sweetly scented with blush-pink flowers. The Dell at Leonardslee is home to a Cornish Red rhododendron planted in the 1800s with curving stems that have grown to a height of 10m.

Use rainwater

Further north, the steeply sided valleys in the gardens of Muncaster Castle in Cumbria (muncaster.co.uk) provide the perfect microclimate for what was once considered the finest collection of rhododendrons in Europe, created by the sixth baronet Sir John Ramsden.

Not all varieties are welcome. In Scotland, R. ponticum has become problematic. It is one of the targets of Project Wipeout, a campaign started by the National Trust for Scotland in 2020 to free the natural environment of invasive plant species.

If you want to grow your own non-invasive rhododendrons or azaleas, choose a site with dappled shade in a sheltered position, with moist, acid soil.

Incorporate organic matter with a high PH into the planting hole, such as composted tree bark, leaf mould, decomposing spruce or pine needles. Don’t plant too deeply — just cover the roots then apply a 7cm mulch. When watering, use rainwater, as tap water contains too much calcium. If you have existing rhodys, apply mulch now.

If your soil is alkaline like mine, try growing compact hybrids in a container filled with ericaceous compost.

R. ‘Percy Wiseman’ is a lovely peaches-and-cream yakushimanum hybrid, while R. ‘Blue Danube’ is an evergreen azalea with violet funnel-shaped flowers. Both hold an RHS Award of Garden Merit.