Deciduous azaleas: the loveliest of the rhododendrons

By Andy McIndoe

Brentry Woodland, part of The Sir Harold Hillier Gardens, Hampshire, England is a sight to behold in late spring when deciduous azaleas set the dappled shade ablaze in shades of flame, orange, pink, yellow and white. Here the soil is acid and quite moist under the shade of mature pines, oak and birch trees. For those of us that live locally, the azaleas in bloom alongside Jermyns lane, Braishfield, which divides Brentry from the main part of the Sir Harold Hillier Gardens are a welcome indication of the beginning of summer. For me they are a delight on my way to and from the office. When in bloom its windows down and take in the fragrant air: a fillip at the beginning or end of the day.

In the azalea season I always try and visit the woodland one early evening to enjoy these wonderful plants at close quarters. The fragrance of many is so delicious and their colours warm and welcoming. They sit alongside evergreen rhododendrons, magnolias, ferns and gunneras but for me the deciduous azaleas are the stars of this late spring show. The Gardens, formerly the Hillier Arboretum were started in the mid 1950s by the late Sir Harold Hillier. He would only have known these plants as smaller less mature subjects but I have no doubt that his vision imagined what they look like today. Many are towering specimens of great character: open shrubs with elegantly poised branches carrying delicate bouquets of blooms. The woodland setting suits them perfectly as they line the sandy path that follows the contours of the undulating ground.

Growing deciduous azaleas

Deciduous azaleas are all Rhododendrons botanically; this can be confusing for many gardeners. They need a soil that is on the acid side of neutral; moist but well drained. They are difficult to establish on very dry soils; I have found this in my own garden. Where I have succeeded I have added copious amounts of leaf mould and moss peat. The latter is rarely used as a soil conditioner in the UK today for environmental reasons. All rhododendrons are ericaceous plants and as such are light feeders. They do not appreciate copious supplies of manure and standard fertilisers; instead they need a slow release fertiliser specifically for ericaceous plants. They can be grown in pots and containers using a loam-based ericaceous (lime-free compost). Deciduous azaleas can be grown in sun but they are at their best in semi-shade; ideally under the dappled shade of trees. Older shrubs can be pruned immediately after flowering to stimulate new, vigorous growth. Old, tired azaleas can be cut back hard at this time to rejuvenate them.

Planting design with deciduous azaleas

I always use a number of deciduous azaleas in my exhibits at RHS Chelsea Flower Show. They are popular with the staging team for their open, graceful habit which means they sit happily alongside other subjects. Their evergreen cousins, the large leaved evergreen rhododendrons and evergreen azaleas are invariably heavier and more solid in character. This is also true in the garden where their open habit is useful to lighten heavier evergreen neighbours. They also have a see-through quality, even as young plants so you can use them further forward in the planting picture and look through them to other subjects or the vista beyond. This gives a planting greater depth. A deciduous azalea in a large container near to the house can create excellent foreground interest magnifying the perspective, making the garden feel larger. The branch framework of deciduous azaleas has maturity and character, even from an early age. This makes them flowering alternatives to Japanese Maples in the open ground or in pots.

Japanese Maples make good planting partners for deciduous azaleas, particularly those acers with wine coloured leaves. These are particularly lovely with any of the flame, gold or orange shades of azalea.

If you have the right soil and a little space use deciduous azaleas to line a path; this is a wonderful way to enjoy their colours and fragrance and to watch them mature over the years. If you only have a small garden then choose one with a delightful fragrance such as ‘Irene Koster’, ‘Northern Hi-Lights’ or ‘Daviesii’. A single plant of any of these will fill the garden with its sweet fragrance.


The bonus of fall foliage

So far I’ve only talked about flowers; all rhododendrons excel in spring. However an evergreen rhododendron is little more than a laurel once those gem-like blooms have faded. A deciduous azalea on the other hand has softer-lighter foliage and most varieties display incredible shades of autumn colour in their fall foliage. Take the honeysuckle scented Rhododendron luteum for example. This has delicate soft golden-yellow flowers in late spring; the fragrance is powerful and bewitching. I autumn the leaves change to shades of glowing copper and flame. It is a relatively slow growing species with slender branches and an attractive framework.

Rhododendronluteum - autumn

So which varieties are the best?

This is a difficult one because there are so many beautiful cultivars to choose from. Here are a few of my personal favourites:

‘Fireball’. Glowing flame red blooms in tight clusters. Slight fragrance. Not in my usual colour palette but I love it with blue Iris sibirica and the gold foliage and orange tips of Spiraea japonica ‘Firelight’.

‘Iren Koster’. Soft salmon pink blooms with hints of gold; beautifully poised and deliciously scented. plant it with a red-leaved acer or Physocarpus ‘Diable d’Or’.

‘Daviesii’. Almost white with hints of gold. Perfect open blooms and a fairly compact habit. Fragrance outstanding.

Rhododendro luteum. I’ve said it all above! Everyone should have it.

‘Homebush’ Rounded heads of hose-in-hose flowers of deep pink. Interesting habit and long-lasting blooms but no scent.

‘Cannon’s Double’ Divine large hose-in-hose flowers of clotted cream blushed strawberry pink. Fantastic autumn colour. No fragrance: you can’t have it all!

And your favourites? Do tell us all about them. I’ve just had my annual injection of deciduous azaleas so I’m inspired, I hope you are too.

Andy McIndoe

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