Dendrobium sect. Rhizobium Lindl. was established by John Lindley in 1851 based on Den. linguiforme. This classification was used by Schlechter in his major revision of Dendrobium in 1911-14. Brieger proposed in 1981 that this group be separated as a new genus Dockrillia, but this was rejected at the time. Section Rhizobium includes around 30 species, which are mainly centered in Australia (17 –18 species) and New Guinea (10 species so far described), with others in New Caledonia, Fiji, Tahiti, Samoa, Aru Islands and Vanuatu. Like so many orchids, name changes have been common over the years – for example Den. striolatum Rchb.f. was described as Den. teretifolium (1839), Den. milliganii (1859) and Callista striolata (1891) (Clements 1989).
The species are very variable in leaf form and flowers, which are commonly non-resupinate, appearing upside down. This feature can also be seen in the other Dendrobium sections Conostalix and Lichenastrum. Plants are usually found at low to moderate altitudes, growing as epiphytes or lithophytes in rainforests and open forests, often in bright light. The brighter the light the redder the growths become, due to the presence of anthrocyanins.
There has been a rise in popularity of these cool growing plants in the past 20 years, and I feel that there is much potential for further work in hybridisation. The crucial work in these hybrids was done by Neil Finch, Phil Spence and Brian Gerhard in New South Wales, and more recent work by George Byrne-Dimos, Wayne Turville and Jeanne Dunn in Victoria.
Having acquired over 500 Rhizobium hybrids and species as part of the Down Under Native Orchids enterprise (DUNO) it was important to establish a new line of breeding, thus this article is a collection of my thoughts on previous results and future directions.. I reflect on hybrids I consider are ‘staples’ for future breeding and those that have made a substantial impact to date. I will also explore more recent hybrids that have proven their worth, and crosses made with plants that show promise. Some confusion in use of species and registration of early sect. Rhizobium hybrids, particularly with regard to Den. fuliginosum, has been discussed in Orchadian previously (Gerhard, 2014).
The two earliest hybrids were made by Noel Jupp – Den. Virginia Jupp in 1969 (Den. linguiforme x Den. teretifolium) and Den. Rosemary Jupp in 1975 (Den. striolatum x Den. teretifolium).
Dendrobium Australian Ginger (registered by Australian Orchid Nursery (AON), 2003) was the hybrid that demonstrated what is achievable by knowledgeable individuals. DUNO has sown around 15 variations of Den. Australian Ginger using different forms of Den. striolatum. For a primary hybrid between Den. fuliginosum and Den. striolatum the shape of the flowers and the colouration can be very attractive. Even when Den. striolatum was used as the pollen parent it was evident that substantial amounts of colour was transmitted to the progeny. Dendrobium striolatum ‘Ruffles’ FCC/AOC-OSNSW AM/ANOS provided its progeny with broad labellums and large frills while still maintaining rounded segments and good colour saturation, mainly of the petals. Dendrobium striolatum ‘Tasmanian Gold’ created an intensity of gold with a burgundy ‘spray can’ affect, the most pleasing colours by far.
Dendrobium Tweetie (registered by Phil Spence, 2002) is a standout example of innovative breeding. A primary hybrid between Den. fuliginosum and Den. convolutum, the seedlings have intense colours ranging from sandstone yellow with a red labellum and matching column and central, to dark burgundy. This primary hybrid also has reasonable shape I have not seen a Den. Tweetie that is not aesthetically pleasing - our seedlings ‘Huge’ and ‘Pie’ are good examples. The selfing of Den. Tweetie ‘Huge’ further intensified colour and improved shape and size - ‘Jester’, ‘Harlequin’ and ‘Rich Port’ are examples .
Dendrobium Tweetas (registered by DUNO, 2005) is Den. Tweetie crossed with Den. striolatum. Several different Den. Tweetas were sown by DUNO. The most outstanding results were from cross 1877 using Den. striolatum ‘Tasmanian Gold’. These hybrids had intense colour. However, as usually the case when Den. striolatum is present in the immediate gene pool, flower count was reduced, and this is something to be considered in future breeding.
There are three main plants of Den. Oliver Jack that have survived from the original crossing by Neil Finch (registered 2004) - ‘Gerard’ AM/AOC-OSNSW HCC/ANOS, ‘Oliver’ (Grand Champion of the Hunter Wetlands Festival in 2009) and ‘Five Things’ (named because there were five seedlings growing when Brian Gerhard took over DUNO). The cross used Den. Jiggi ‘Best Blue’ and Den. striolatum ‘Neville’. Dendrobium Jack Tinson (registered DUNO 2012) is the next generation, Den. Oliver Jack x Den. striolatum, and it has produced excellent results
Dendrobium Grumpy (registered George Dimos 2005) has proven ability in breeding. The parents are a crossing of Den. Aussie Phil x Den. striolatum and the seedlings boast a large, broad labellum and extremely large segments that are layered with striations of grey-brown tones, leading to some dull-coloured flowers. Dendrobium Kalon Byrne-Dimos (Den. Bill’s Dorn x Den. Grumpy, registered 2012) is a successful next generation.
Staples for the Future
We acquired several seedlings of Den. Kalon Byrne-Dimos from Orchids on Newbold which have now grown into large plants. They have lovely clean coloured flowers, well proportioned flower segments, large labellums and the flowers are huge In 2015 we have had successful germination finally with Den. Kalon Byrne-Dimos ‘Newbold’ as a parent.
Dendrobium Sharday (Den. Tweetie x Den. chordiforme) has only just started to flower in recent years. It was bred by the late Brian Gerhard (registered 2013). These plants flower throughout the year and usually have a high flower count, depending on the time of flowering. Most have been cream-based flowers with the pleasing ‘spray can’ effect. I believe the classical shape and high flower count will produce great progeny in future lines.
Dendrobium Granma is Den. Sylvester x Den. Tweetie (registered DUNO 2014), and again shows the success of Den. Tweetie as a parent. Dendrobium Granma ‘Ruby Lips’ is one of the most pleasing Dendrobium hybrids I have seen, with its contrast of colours and good shape. It is, however, a very shy breeder and we are yet to achieve a successful pollination.
Using Den. Grey Ghost ‘Tumbi’ HCC-AD/ANOS (Den. striolatum x Den. Rosemary Jupp, registered DUNO 2006) can achieve further progress in a breeding program. It has already produced large almost blue-wash hybrids in Den. James Garner (registered DUNO 2013).
Dendrobium Harmon ‘Mark’ (Den. Rosemary Jupp x Den. grimesii, registered DUNO 2010) is one of the most unusual colour variations we have flowered. It has a salmon pink base with striations of a slightly browner colour. Both its growth and inflorescences present upright and carry on average 10 flowers. The only issues for ‘Mark’ are of small size and a small labellum. We are yet to flower Den. Harmon x Den. striolatum and Den. Harmon x Den. dolicophyllum, and this year have headed in a new direction with Den. Harmon x Den. Rocky Carroll.
Dendrobium Martin ‘Gold’ HCC/AOC-OSNSW is Den. Aussie Phil x Den. Duffy (registered Jeanne Dunn 2008). It has produced plants with surprisingly high flower counts. In 2015 it won Reserve Champion at the Bellinger Valley Orchid Society and also Champion Australasian Hybrid at the Central Coast ANOS spring show. I believe its wide labellum of contrasting purple and its olive green segments may produce superior single colour flowers that will perform well on the show bench.
We purchased a flask of Den. Australian Purple Pepper from Phil Spence (registered AON 2007) in the early 2000’s and grew about 50 plants on to flowering. This year several plants were identified to be used in the breeding with potential in their high flower counts, vast range of colour variations and great shape. We have had quite a number of successful crosses in 2015, for example using Den. Grumpy, Den. Jiggi and Den. Weatherly.
Dendrobium Hunter Sand Dune (Den. Tamara x Den. teretifolium) was crossed by Brian Gerhard around 2008 (registered Callyn Farrell 2015) and only 10 seedlings were de-flasked. We were given half and have since flowered all five. These plants have a high flower count but have been light on for the number of inflorescences. In 2013 we crossed it with Den. Australian Freckles and Den. Weatherly aiming to rectify these faults.
Dendrobium Lauren ‘Holly Chief’ (registered 2009) was awarded HCC/AOC-ANOS at the 2015 Kempsey Speciosum Spectacular. Brian saw the capabilities of this plant and since then we have flowered Den. Lauren x Den. Australian Ginger. The results have been exciting. The shape, flower count and ease of growth have all carried through to the progeny. We have used it in 2015 for several hybrids, and feel the wide labellum and the expansive size of the flowers will produce worthwhile results.
Flower count, shape and size are crucial elements which in the past have been overlooked. Looking to the future, some outstanding colour combinations and larger flowers can be expected by further breeding using Den. dolichophyllum , Den. Jiggi, Den. Oliver Jack ‘Gerard’, Den. Grey Ghost ‘Tumbi’, Den. Lauren ‘Holly Chief’ and Den. Martin ‘Gold’. We are also endeavoring to increase the flower count by the use of Den. Australian Purple Pepper, which have been carrying 10-20 flowers on their second flowerings in 100mm pots.
In my opinion there is a very exciting future ahead for this particular section of Dendrobium. If careful decisions are made in terms of their breeding these pleasant native orchids will continue to improve and develop.
Brieger FG. (1981). Subtribus Dendrobiinae. In: Brieger FG., Maatsch R., Sanghas K. (eds.). Die Orchideen 3rd edn (11-12). R. Schlechter. Parey: Berlin, 636-752.
Clements M.A. (1989) Catalogue of Australian Orchidaceae. Australian Orchid Research Vol. 1. Australian Orchid Foundation, Essendon, Victoria.
Gerhard B. (2014) Mystery regarding use of Dendrobium (Dockrillia) fuliginosum, alias Black Pam. The Orchadian 17:553-557.
Lavarack B, Harris W, Stocker G (2000) Dendrobium and its Relatives. Timber Press, Portland, Oregon