Rhododendron 'Songbird' and some of its Kissing Cousins
Created | Updated Jun 22, 2002
Having acquired his first garden, quite some years ago now, a young fellow sought advice of his mother as to what to plant in it. The advice was simple: 'If you can grow Rhododendrons, that's what you grow'. At first, he was puzzled. A Rhododendron was a garage-sized hummock of dull green strappy leaves native to Bingley municipal gardens that occasionally sprouted clumps of puce or measled-magnolia trumpets. His new garden would just about fit underneath one.
This young fellow like many others then and now, would not have recognised Rhododendron 'Songbird' as a Rhododendron. The bright-olive, oval leaves are scarcely an inch in length, and the thigh-high, open, tiered structure more reminiscent of a stately specimen tree in miniature than much else. The 'oriental' form and elegance certainly gives it a bonsai feel and it wouldn't be difficult, given a wok-shaped pot and some fancy gravel to pass it off as such. The exotic nature of the plant is enhanced by the brief easter floral display of electric blue often repeating in the autumn.
Some Promiscuous Origins
But a Rhododendron it most certainly is, though not however, a simple distinct species. A brief foray into the murky worlds of commercial horticulture, taxonomy, and plant genetics is necessary to explain. Species names - such as that of Rhododendron augustinii - are Latinised, italicised and without asterisks. R. augustinii, a native of the mountain valleys of the Chinese-Tibetan border, is of limited commercial value in itself. Growing to over 12 feet in height and being a little susceptible to heavy frosts, it is one for the enthusiast rather than the major European and North American markets. What it does have, however, is nice willowy foliage and, in some of the naturally occurring forms, gorgeously cool blue flowers. If this colour could be found in a smaller, hardier plant, its market could increase in numbers from thousands to millions. Now Rhododendrons have a little more reproductive flexibility than we do and this often includes the ability to interbreed with a number of related species. A pretty little mountain dwarf with purple-blue flowers from nearby Yunnan province, R. impeditum, happens to be sexually compatible with R. augustinii, producing offspring given the general technical designation R. augustinii x impeditum. These hybrids are very variable in form, each inheriting a different mix of characteristics from each parent. The plant breeders tried this many times looking for forms with the blue flowers of R. augustinii, but closer in size and hardiness to R. impeditum. Such selections made from cultivated stock are called 'cultivars' and given non-italicised, non-Latinised cultivar names within apostrophes. The random nature of sexual reproduction means that cultivars do not in general breed true, indeed some are sterile, but the strain may be propagated indefinitely by vegetative means giving a form of immortality to one fortuitous plant. One cultivar so developed was given the name R. 'Blue Tit'. Growing to 3 feet it is the right size, moderately hardly and still popular, but the pale, slightly washed-out blue of the flowers left room for improvement. R. russatum is another high alpine Yunnanese dwarf, one form being a delicious indigo in flower. This was crossed with R. 'Blue Tit' and from the hybrid offspring emerged R. 'Songbird'.
Click on this external link to view Rhododendron 'Songbird'
Cultural Requirements of Rhododendron 'Songbird'
R. 'Songbird' inherits some liking for direct sunlight from its two high alpine ancestors, but may be grown quite happily in the the dappled shade of a woodland setting that most Rhododendrons prefer with both moisture and air around its roots.
Preferred Soil Conditions
Rhododendrons hate lime and not many will survive even neutral conditions. The best conditions are free draining acid sandy soils enriched with organic material, though heavy acid clays may also be satisfactory if waterlogging, surface compaction and drought are all avoided. This is best accomplished by digging in a deep surface dressing of grit prior to the planting which must not be too deep and should incorporate an acid organic soil improver - traditionally ericaceous compost but well rotted leaf mould is quite satisfactory if the surrounding soil is naturally acidic. All are shallow rooting and therefore the condition of the top layer of soil is of paramount importance. All benefit from a deep annual mulch of compost.
Propagation
The traditional way of progating Rhododendrons is by layering though this is quite difficult with the somewhat stiff, twiggy branches of R. 'Songbird'. The alternative method is to take semi-ripe cuttings in late summer. As previously stated, the hybrids do not come true from seed though it can be diverting to collect some to see what comes up. Generally, plants are dead-headed as soon as the flowers have gone over to prevent plant from wasting energy on seed production.
Pruning
Pruning is hardly ever necessary, particularly with the smaller forms. More frequently, drastic surgery may be required to rejuvenate a plant that become leggy, badly damaged, or discoloured, most cases of which can generally be attributed to poor siting. All things considered, the best remedy here is to hack everything down to within six inches of the ground, dig up the rootball, and transplant in a more suitable location. This is something of a kill or cure strategy however.
Selected Species and Varieties
Any good gardening encyclopaedia will provide a list of at least 40 good proven hybrids and a handful of interesting species for the casual gardener to try. Unfortunately, these are highly unlikely to be available at the local Garden Centre - the economics of the industry do not work that way, and the shelves are likely to be stocked with this years crop of new hybrids. The following small represented selection shall however, may be obtained from specialist suppliers. All are suited to a UK climate - apologies to the rest of the world but some basis of selection must be adopted!
(Click on external links for photographs)
G. acaulis : The 'Stemless Gentian' is less fussy about soil pH than most, and often provides an Autumn repeat of the Spring showing of green-spotted deep-blue trumpets on short stems (acaulis = 'without a neck').
G. asclepiadea (Willow Gentian) : One of the easiest Gentians with arching 3 foot (1 metre) lax stems terminating in sprays of deep-blue trumpets. Suitable for a moist perennial border.
G. clusii (Trumpet Gentian) : Low rosettes of oval, glossy leaves bear azure-blue trumpets in early summer. Less choice than others, but tolerant of alkaline soils.
G. lutea (Yellow Gentian) : Erect unbranched perennial with whorls of tubular yellow flowers in pale green bracts. Imposing and unusual for those who can manage to get it established.
G. septemfida (Crested Gentian) : The first Gentian to try for those with a heavy clay soil, providing drainage is reasonable. Irregular hummocks of foliage become smothered in mid-blue trumpets in late summer.
G. sino-ornata : Classic, evergreen, prostrate and spreading perennial from South-West China that yields the richest of blue trumpets among the fallen leaves of late-October/November. Needs moist soil and acid conditions.
G. verna : Tubular bright-blue flowers held above small rosettes in spring. Given very gritty, humus-rich soil, this little gem can still be sulky and short-lived.
Permutations and Combinations
Hybridisation programmes continue as urgently as ever to develop not only hardiness and colour (a true royal blue would be nice), but also resistance to the three great enemies of the genus: drought, direct sunlight, and non-acid soils. Yet despite these limitations that deny the genus to so many gardeners, those who can grow them do grow them because no other family comes close in providing such a variety of year round structural interest and colour, into to the garden. Characteristics currently available include:
- Size: From domed sub-shrubs less than 6" high to trees exceeding 50 feet.
- Hardiness: From creeping mats of the exposed coasts of Far Eastern Siberia to tropical epiphytes from the Malaysian archipelago
- Colour Range: Flowers range from pure white through every depth of pastel hue to purest crimson, scarlet, tangerine, apricot, lemon, acid yellow, electric blue, indigo, violet, purple with or without a variety of contrasting frills, spots and blotches
- Foliage: From fingernail sized glaucous blue discs lengthening to ovals of acid to deepest green and eventually the long, leathery straps of most of the larger species. Some species are deciduous and many of these have excellent autumn colour.
If such variety is is impressive, then consider the potential to come from future hybridisation programmes:
- R. 'Songbird' - one clone of R. russatum x (augustinii x impeditum) - is 25% R. augustinii due to the fact that it is two generations removed. Introducing it one generation earlier halves the contribution, one generation later doubles it - eg R. augustinii x (impeditum x russatum) would contain 50% R. augustinii.
- If finer control over the percentage of R. augustinii were required, it could be introduced into more than one generation effectively crossing it with its own offspring. For instance, a hybrid containing R. augustinii in both the second generation back (25%), and the fourth (6.25%), would possess a cumulative total of 31.25%. In theory, any number of sexually compatible forms may be genetically mixed in any proportion.
- Nature has also been hard at work modifying Rhododendron DNA. For example, there are four distinct subspecies of R. augustinii and one of these, R. augustinii ssp. augustinii has eleven scientifically described, discrete forms.
- R. augustinii is only one species of many. As of 1996, the most widely accepted scientific directory of the Rhododendron genus1 listed 1,025 different species.
On the face of it, there should beNow the commercial interests of the The upshot of this is, that if you go to a Garden Centre to buy a Rhododendron, you really have to know what you are looking for. Unfortunately, this requires some knowledge of how the family is classified, and this really is something
Selected Species and Varieties
Today we now have 1,025 species, and countless varieties lumped into one genus. Yet, with less than twenty plants at his disposal, Linnaeus, the founding father of taxonomony, originally specified two genera differentiated by their sexual characteristics. Those with ten stamens he placed in genus Rhododendron; those with five became genus Azalea. Plant classification all went downhill from there, really and confusion continues to reign among horticulturalists at least, though there have been signs over the last decade that the scientific community has begun to
Selected Species and Varieties
Garden Virtues
Automatic choices for the Alpine rock garden, troughs, scree gardens etc. for colour late in the year. Elsewhere in the garden, the beauty and intensity of the floral display is worth the effort of cultivation.
Versatility
- Underplant deciduous ferns with a 'Gentian Lawn' of G. sino-ornata . Quietly serene until it turns blue beneath the autumn tints.
- Many high Alpine gentians are extremely tolerant of cold and wind.
Pleasing Associations
In the main Gentians mix most comfortably with stone and gravel.
Botanical Details
Many so-called 'gentians' belong to the closely related genera such as Gentianella.
Family
Gentians give their name to the Gentianaceae, a Family defined as consisting of 'sympetalous dicotyledons with corolla twisted in bud and unilocular ovary'. It contains about 80 genera and 900 species, though few are widely known.
Related Genera
- Eustoma - Prairie Gentian.
- Exacum.
- Gentianella - Felworts.
- Menyenthes - Bog Bean, Buckbean.