Deciduous Rhododendrons

Sooner or later every gardener in Europe and North America becomes aware of the Rhododendrons. Usually the first encounters are with large evergreen shrubs laden with large trusses of beautiful flowers. It’s easy to get seduced by these showy plants, especially when they flower so magnificently after a dark and dismal winter.

For many there is a temptation to bring the beautiful spectacle home, and there are many garden centres and nurseries that are able to supply a bewildering range of Rhododendrons. And the range is bewildering; it’s generally accepted that there are around 1,000 species of Rhododendron in existence, and God alone knows how many hybrids. Much like the species, hybrids range from vast trees down to tiny miniature shrubs, and while the bulk of Rhododendrons are evergreen there are many deciduous species and hybrids to choose from.

Before we go any further we need to look at the whole ‘Azalea’ issue. Even now the nurseries will sell you a Rhododendron OR an Azalea, but in truth these are scientifically regarded as one and the same, that is to say that ‘Azalea’ is part of the genus Rhododendron, so a plant labelled as ‘Azalea X’ is in fact ‘Rhododendron X’. There are superficial differences between the two genera but they have more in common; under the old naming there were deciduous and evergreen Azaleas and Rhododendrons, neither had a monopoly on being dwarf or large, neither were always scented or always lacked scent, and they have a lot in common genetically. The genetic study of the two genera brought them very much together, and in fact threw up an interesting anomaly- evergreen and deciduous Azaleas weren’t actually that closely related to each other!

I won’t go on about this too much because if you want to know more there are many other resources that will explain it better than I can, but in a nutshell here we go…. Genetic testing allows the species of Rhododendron to be grouped together in the same way that genetic testing of people shows who is genetically related to who. If you arrange the species together you can create a list that shows, in order, how each species is related. Adding the Azaleas to the mix brought up quite a surprise; deciduous and evergreen azaleas are at opposite ends of the list! Consequently the whole genus ‘Azalea’ is now a group within the Rhododendrons.

So you decide that you want to enjoy some beautiful Rhododendrons in your garden, and who could blame you? Before you devote an area of your garden to Rhododendrons, I would like to make some points in favour of deciduous species and hybrids.

First there is foliage. Rhododendron leaves can be fantastic and can even eclipse the beauty of the flowers, but they can also be very dull and nondescript. It is very important to choose carefully; once the flowers have finished for the year you’re left looking at the foliage, so the plant must either have interesting foliage or must be neutral so that it disappears into the background. This is where so many of the hybrid Rhododendrons fall flat… once the incredible show of flowers is over the plant becomes so boring! Most of the hybrids available to gardeners make domes (of various sizes) of dull leathery leaves. On a small plant you can hide this problem by growing something big in front of it, but the truth is that too many Rhododendrons make ‘lumps of shrub’ that stick out like a sore thumb in the garden during summer. By contrast deciduous Rhododendrons have fairly small leaves which, although not greatly beautiful, become a neutral background in a garden. They also have a softness about them that helps them blend in. It’s worth noting here that some evergreen Rhododendrons can suffer badly with spotting and winter damage, but as the deciduous Rhododendrons lose their leaves this is seldom a problem.

Then there’s the matter of shape. Rhododendron species and hybrids come in various sizes and shapes, but a significant majority of the hybrids make rounded ‘bun-shaped’ plants. Again with small plants this isn’t as much of a problem, but a tall and wide Rhododendron in a small space can be a real nuisance if it’s not really special. There are wide-spreading deciduous species but thanks to their finer foliage they seldom look quite as oppressive as their evergreen relatives. Typically though the majority of deciduous Rhododendron species and hybrids appear (certainly in my experience) to be more upright or vase-shaped. This has two big advantages; it makes for more ‘shapely’ plants if they’re grown in isolation, but also it leaves room at the base for other things. Now, here we must tread carefully as Rhododendrons are shallow rooted and dislike competition at their base, but the space allows spreading plants like Geraniums to ‘flop’ around the base of the Rhododendron, giving the gardener more flexibility to create beauty.

Florally speaking the deciduous Rhododendrons are at least as good as most of the evergreens. Certainly the hybrids often have large showy flowers with beautiful markings that you would see on evergreens, but here’s where the deciduous hybrids overtake their evergreen kin; while both cover shades of whites and pinks admirably the deciduous hybrids are the masters of the fiery reds, oranges and yellows. The contrasts between the ‘pale’ and ‘flame’ colours can make for some horrendous combinations, so please pick one set of colours and go with it rather than trying to mix them up! And yes, the evergreen Rhododendrons come in shades of red, orange and yellow too, but without the same undeniable quality of colour.

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*Rhododendron ‘Niveum’ is officially semi-evergreen but holds onto so few leaves that it might as well be deciduous!

For me a really big plus for the deciduous Rhododendrons is their autumn colour. Even with the best foliage, the evergreens really are ‘ever green’; apart from the flowers in spring where is the seasonality? You have a plant which squeezes all of its excitement into a relatively short period in spring and then appears inactive for the rest of the year. Compare this with deciduous species and cultivars which have the excitement of breaking buds and bold flowering in spring but then also a contribution to the autumn display- certainly to my mind this gives the deciduous cultivars a bit of an edge.

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Going off topic… When I’m looking for plants for a garden I’m keen to pick plants that contribute all year round, but increasingly I’m of the opinion that some plants contribute by their non-contributing! Modern garden planning has this idea that you must have lots of evergreens and lots of ‘winter interest’ plants in order to have a successful and enjoyable garden. I’m not in horticulture to be popular, so please indulge me while I tear down convention:

1. Yes, evergreens give ‘structure’ and privacy during the winter. This is because they are ‘solid’ features, that is to say that they usually don’t allow light through in the way that bare branches do. Evergreens also rarely ‘do’ anything; Ilex sometimes have fruits and/or variegated leaves, Taxus look pretty much the same all year (barring fruits, which are seldom concentrated enough to have a big visual effect like the Ilex), Camellias and evergreen Rhododendrons look the same as they did in summer and wait until spring to flower… Over-reliance on evergreens gives you are garden which looks surprisingly similar for most of the year. I advocate an 80:20 rule, where 80% of the plants in a garden are deciduous while 20% are evergreen.

2. Beware of getting sucked into growing plants for ‘winter interest’ like coloured-stemmed Cornus, Salix or Acers in great numbers. Much as with the evergreens they lose their impact if you plant too many of them, unless you’re able to dedicate vast areas to planting. There is nothing more depressing than a trio of Salix ‘Britzensis’ in the middle of a bare border, knowing full well that during the summer the border is trying to be showy with three dull and uninteresting willows in the middle- choose plants and locations carefully, creating well-placed focal points for winter without making awkward and uncomfortable planting for summer. Winter is the opposite of summer; summer is bright, colourful and lively while winter is dark, cool and sombre, so enjoy the winter and its plants but don’t try to plant your garden so that winter ‘replaces’ summer (unless you have a vast dedicated area to do it, in which case go for it).

Back on track…. The bare stems of deciduous Rhododendrons are perfect for winter. They’re an anonymous reddish colour and make no attempts to dominate. Having lost their leaves they allow the meagre winter light in, so can have a real added benefit in making a garden feel bright and light for winter, while the dark evergreens can leave a space feeling drab.

If you’ve made it this far you’ve probably gathered that I have a fondness for deciduous Rhododendrons. I really genuinely feel that they have so much to offer, especially in smaller gardens, and hope that maybe others will begin to look at them as a valid alternative to, if not improvement on, the evergreens.