Oceania Orchids
Darryl and Alison Smedley

By David P. Banks dpbanks@ozemail.com.au and Darryl Smedley dsmedley@ozemail.com.au

(This article was originally published in The Orchadian Vol.12 No.4 June 1997)

Dendrobium lawesii is one of the easiest New Guinea orchid species to cultivate in a glasshouse or shadehouse as far south as Sydney, NSW. Like the ever-popular and desirable D.cuthbertsonii, it comes in a wide range of colours. The most common being red, but in a number of shades. It also occurs in orange, tangerine, yellow, purple, pink, blue(ish), and apparently even white. Next comes the bicolours. We have seen red with purple distal parts, pink and white, orange with a purple ovary and orange with a pink wash. No doubt there are others.

History and Etymology

The Rev. W.G. Lawes of the London Missionary Society is credited as the discoverer of D. lawesii. He sent specimens from the the British New Guinea to the Victorian Colonial Botanist, Baron Sir Ferdinand von Mueller, who named it after its collector and described it in the June 1884 edition of the Melbourne Chemist.

Many Australiasian species were subsequently named by von Mueller, and his name is well known to students of Australian orchids.

Distribution

Dendrobium lawesii occurs throughout New Guinea, where it can be quite locally common, through Bougainville and the Solomon Islands. D. lawesii does not occur in Vanuatu as the botanist Kraenzlin confused it with the closely related but distinct D. mohlianum.

It is often found in mountain forest, at times in quite low light, from 500 to 2000 metres above sea level. We believe that almost all of the material in Australian collections is from Papua New Guinea.

D. lawesii is one of the members of the colourful Calyptrochilus section of Dendrobium which is in need of revision. Schlechter made the comment in his opus The Orchidaceae of German New Guinea that this species may be regarded as the most common in this section.

D. lawesii is an epiphyte with pseudobulbs up to 90 cm in length, however they are commonly half this length. They are pendent and the darker coloured clones have maroon leaf sheaths. The leaves are distichous, up to 60 mm long and 20 mm wide and are produced along the length of the pseudobulb. Up to ten bell-like tubular flowers are produced in often downward pointing clusters.

A curiosity of this species, as with others in the section Calyptrochilus, is that the root tips are orange rather than green as in most other members of the Orchidaceae.

The pollinator is presently unknown for this species however it is most likely bird pollinated due to the configuration of the flower. D. lawesii grows in areas where there are epiphytic Rhododendron species which have somewhat "similar" shaped and coloured flowers. It is certainly not dismissed that the orchid could be mimicking the rhododendrons to deceive the pollinator.

Results to date indicate that most successful artificial pollinations are achieved when the flowers on the pod parent are from 3 to 10 days old. Fertility appears to decline after this period.

We have now grown quite a number of New Guinea and Pacific Island species to maturity. We have learnt some significant cultural information by comparing results of species grown in each others glasshouses. From the Smedley glasshouse which is relatively warm and well-lit to those grown in the Banks’ glasshouse which is cooler, with higher humidity and more shade. Such co-operative efforts are very helpful in identifying that niche in which plants will perform best.

In glasshouse culture, plants are kept at a minimum of 12° C in winter by a simple room heater controlled by a thermostat.

This species does not require a high level of light being happiest in a spot that could best be described as moderate shade. It even grows quite well when placed under a bench where light level and air movement are at their poorest in a glasshouse. They do however flower significantly better when given stronger - but not direct light. Remember, the flowering inflorescences are produced in almost all instances on well matured pseudobulbs which have lost some or all of their foliage.

Dendrobium lawesii has a relatively fine root system so the potting media should not be on the course side. A seedling grade mix of bark and pebble in the ratio of 4:1 has been used satisfactorily for many years.

Like so many other mountainous epiphytes, the plants also respond splendidly to live sphagnum moss. This is particularly useful when striking aerial growths which appear infrequently, back-cuts of choice clones or desiccated plants.

We have used both plastic and terracotta pots with D.lawesii. Plastic pots certainly keep the mix moister longer, a slight advantage with this species. One thing we are certain of is that D.lawesii does not need to be repotted with any great frequency. In fact, some of the first plants obtained about ten years ago are still in their original 50 mm thumb pots. The plants have almost climbed out of the pots and moss has developed on the surface of the media and exposed root system but they still grow well. The pseudobulbous stems of the plants in these pots have grown to great lengths, 80 cm in the longest, so they have certainly done exceedingly well when the root system is confined.

It will grow quite happily in a Sydney shadehouse all year 'round if not allowed to dry out too much in winter. Flowering seems to be delayed outside compared to cousins in the glasshouse. The outside plants are shy to flower in the autumn and the inflorescences do not develop until more into summer.

D.lawesii generally flowers off the deciduous pseudobulbs for some years although in well-cultivated specimens flowering can occur on the distal portion of the pseudobulb when it is still leafy and just matured. Peak flowering occurs in the autumn then into winter and again in spring but in a collection there always seems to be at least one plant in flower.

The flowers develop in clusters along the pseudobulb and last about 6-8 weeks. A shorter flowering period can be expected if the plants are exposed to moderately high levels of light.

A few nurseries advertise this species infrequently and occasionally mature plants will be released. Nursery raised seedlings are certainly easier to cultivate than bush collected material as they don't suffer the shocks of collection, packaging, air travel and often unsympathetic quarantine.

The red and red/purple bicoloured strains are those most commonly available at present. We are now starting to flower a number of clones from a selected outcross in the yellow to orange shades. Over the next couple of seasons we will know the results of matings between different colour forms.

We wish to thank the following people who, in one way or another, have contributed to our knowledge (& our collections in some cases) of this species. Sid Batchelor, Jim Cootes, Jack Jannese, John Roberts, Phillip Spence, Geoff Stocker, Peter Taylor, Richard Warren and John Woolf. Thanks to Howard Gunn of Sacramento, USA for the slide of his flowering plant. Whilst many of the photographs were taken by one of the authors (dpb) we wish to sincerely thank David Titmuss for the slides he has taken, and continues to take, for us over many years.

Lewis, B. and Cribb, P. (1989) Orchids of Vanuatu. Royal Botanic Gardens. Kew, England.

Millar. A. (1978) Orchids of Papua New Guinea - an introduction. Australian National University Press. Canberra, Australia.

Schlechter, R. (1982) The Orchidaceae of German New Guinea. The Australian Orchid Foundation. Essendon, Victoria Australia.

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