Oceania Orchids
Darryl and Alison Smedley

Notes on the Cultivation of Some New Guinea Species

By Darryl Smedley dsmedley@ozemail.com.au

(This article originally appeared in The Orchadian Vol.11 No.9 September 1995)

It has been obvious to me for some time that there has been a marked increase in the interest in the orchids of New Guinea and other Pacific Islands. There have always been sections on the show bench for Australasian species but they used to only have the odd common PNG species such as Dendrobium macrophyllum or D.polysema or D.helix or a lone D.subclausum (or D.phlox or D.flammula to use some of the names that have been used for this species). There are now a wide variety of species and genera making their appearance indicating the rising interest in these plants. It is not uncommon to have to judge the section when it contains such disparate genera as Bulbophyllum, Mediocalcar, Paphiopedilum, Spathoglottis, Diplocaulobium, Cadetia and the wonderfully different sections within Dendrobium such as Spatulata, Latouria, Calyptrochilus, Pedilonum and Oxyglossum.

Species are slowly becoming available as a small number of nurseries add them to their catalogues. I would venture that there are now more species available than in any other time in ANOS history as the flasking of Australasian species increases. The ban on export of any further live material from Papua New Guinea has certainly stimulated these efforts as no longer can the enthusiast rely on obtaining wild collected stock.

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 difficulty still remains though, of discovering reliable cultivation information on nearly all of the Australasian species. The dedicated grower can infer some information by studying often meagre habitat information scattered through the small number of books dealing with this group of species. For Dendrobium species, the monographs by Cribb on the 'Antelope' Dendrobiums (1986) and section Latouria (1983) are useful as is the revision of section Oxyglossum by Reeve and Woods (1989). Information on Bulbophyllums is very scarce. About the only data available are the articles by Howcroft and Cruttwell as published from time to time in The Orchadian.

Regional accounts of orchid flora from some of the Pacific Islands e.g. Vanuatu (Lewis & Cribb 1989), The Solomons and Bougainville (Lewis & Cribb 1991), Fiji (Kores 1989) and New Caledonia (Halle 1977, the text is French but at least the drawings are in English!) can also give up some information useful to the cultivator.

I have now grown quite a number of New Guinea and Island species to maturity. The following notes are intended to guide the grower new to Australasian species into the cultivation of some easy and satisfying species. A glasshouse is not necessary provided some fundamental needs of the species are understood. Some New Guinea species, such as D.vexillarius, can inhabit zones up to 4000m (Reeve & Woods, 1989) so a heated glasshouse would just about be a death sentence for these plants. If you can obtain the stock it is a good idea to experiment with your plants in different situations within your structures. I have learnt some significant information by comparing results of species grown in my relatively warm and well-lit glasshouse to those grown by David Banks in his glasshouse which is cooler, with a higher humidity and more shade. Such co-operative efforts are very helpful in identifying that certain niche in which cultivated plants will do best.

My glasshouse is not large, only 8'x12' with 7' walls and a high gable. The long axis is oriented North-South with the door in the southern wall so as to gain maximum space in the well-lit end.

It is kept at a minimum of 13 degrees in winter by a simple room heater controlled by an external thermostat. An automatic watering system damps down the floor periodically overnight so that the humidity does not drop dangerously given the drying effect on the air of this type of heater. I don't generally use shadecloth in summer although I threw some over the house last December the day after the ambient temperature reached 49 degrees!. It will come off about Easter. The roof is a double-skinned rigid plastic Nylex product constructed a lot like corrugated cardboard.

All the windows, about 40% of the side wall area, are open all summer and a rotating 24" fan is on all the time. I have traded the fact that the odd bug gets in and munches something for high ventilation. I used to run an evaporative cooler but ceased after the last one broke down under the load. I thought that the high internal temperature reached with the glasshouse closed up so that the cooler could run, combined with the very high relative humidity was not to the liking of many of the plants. I now rely on good ventilation and the automatic watering system misting two or three times a day for reducing the temperatures to manageable levels. Its much cheaper now as it only costs to run the heater and the fan.

The gable space is occupied by a number of D.canaliculatum, D.dicuphum, D.trilamellatum and other tropical species that like warm and high light environments. A neat trick as these plants and their totems provide good shade for the plants down on the next level on the bench and those hung at eye level. You can be quite clever with growing a range of orchids in your glasshouse by proper placement of species with differing requirements.

In mine, the smaller tropical species are in the gable as described. The taller hardcanes are on the bench at the front where the light is high and the warmth comes through the glass at the front. Paphiopedilum species occupy much of the bench space at hip height down the sides. Also there are most of the Dendrobium section Latouria species such as D.otoguroanum, D.alexandrae, D.eximium, D.cruttwellii (one is in the shadehouse all year to compare growth) and D.convolutum. The more robust section Latouria species such as D.macrophyllum, D.polysema, D.finisterrae and D.forbesii are placed more to the front of the house as they seem to prefer reasonable light rather than mostly shade.

The back of the glasshouse has therefore been manipulated so that it is a haven for the cooler growing species, including most of the Diplocaulobiums, Sarcanthinae species, Bulbophyllums, Cadetias etc. It can be real hard to find just the right spot for a high light loving but cool growing orchid in a mixed collection. Fortunately most species are reasonably tolerant so, for the moment, and until a purpose-built structure can be erected, these types of species get the temperature that they need but miss out a bit on light. They grow alright but don't flower all that well. Besides, a drop in light intensity won't kill them but exposure to high light and low humidity will.

The space below the bench is not wasted as there hang most of the Bulbophyllums in the collection. Some, like B.nasica and B.fritillariiflorum, do terrifically well down there growing rapidly and flowering regularly. Unfortunately, some grow rapidly and flower wretchedly. These species, such as B.tollenoniferum, B.tortum and B.masdevalliaceum would probably flower if they received more light. Sad to say but they're not going to get it at the moment because there just ain't no room for these robust plants upstairs. When the new glasshouse comes everybody can have what they like. Have you heard about Rule One of glasshouse culture? Build it twice as big as you think you need it and then it will be only half as big as you require.

There is a very low bench at the front as well where some of the lowland but non-high-light plants live. Coelogyne fragrans, B.graveolans, Eria species and our own Phaius pictus and Malaxis species do well there.

My shade house has been described previously, see Smedley (1992). Most of the more robust Dendrobium species are moved out there during the summer months and generally returned to the glasshouse by the end of March, sometimes a little later if autumn is warm. Once you get a few nights in a row bottoming at 10 degrees it is time to make the move. Outside the plants are refreshed by rain water, growths are stronger with the higher light, they are better ventilated and any flowers produced in the period have a greater intensity of colour, no doubt induced by the greater exposure to ultraviolet rays. The species that overwinter in the shadehouse are generally placed in their pots on trays half-filled with a pebble and sphagnum moss mixture. This mix is kept moist which helps to raise the humidity around the plants when the ambient humidity is low.

Now to some species accounts.

Dendrobium lawesii

This species is one of the easiest New Guinea species to cultivate in a glasshouse or shadehouse as far south as Sydney. Like the ever-popular and desirable D.cuthbertsonii, it comes in a wide variety of colours. The most common appears to be red but in a number of shades. It also occurs in orange, yellow, purple, pink, blue(ish), a sort of tangerine and even white. Next comes the bicolours. I 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.

D.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. 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 Family Orchidaceae.

I have used both plastic and terra-cotta pots with D.lawesii. I don't think there is much difference apart from the plastic keeping the mix moister longer, a slight advantage with this species. Of one thing I am certain is that D.lawesii does not need to be repotted with any great frequency. In fact, some of the first plants I obtained over eight years ago are still in their original 50mm 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, 80cm in the longest, so they have certainly done exceedingly well when the root system is confined.

The 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.

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. 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.

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 when compared to its cousins in the glasshouse. The outside plants are shy to flower in the autumn and the inflorescences do not develop until more into summer. 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.

This species is one of a group of three higher altitude species of antelope orchids in the Section Spatulata. The others are D.magistratus and D.hamiferum. It is a relatively recently named species having been described in this journal in 1980 by Cribb (1980) from material collected from the Eastern Highlands districts of Papua New Guinea. The altitudinal range of the species is given as from 1100-1450m.

From this altitude a degree of cold tolerance could be expected. So, when I received my first plants in 1989 (from Geoff Stocker, Malanda Qld) I decided to conduct a comparative test of this tolerance.

Identical seedlings were potted up and put into the glasshouse and shadehouse. The glasshouse seedling first flowered in 1992 and has flowered each winter since. The mature pseudobulbs are up to 90cm tall. The plant in the shadehouse has grown steadily but has not yet flowered. The lead growth is only 20cm tall but I expect the next growth to flower as the glasshouse seedling first-flowered from a pseudobulb only 30cm high. I have concluded that this species is certainly tolerant of the cold of a Sydney winter but that it will do much better in a heated glasshouse.

I have also had a tray of seedlings out over winter without contracting any of the blemishes characteristic of cold damage. They only started to move after the worst of the summer heat was over. Obviously, D.crispilinguum doesn't like the heat of high summer when young.

The adult plants mature growths without difficulty in the glasshouse. Growth is rapid and the growing pseudobulbs do not appear to be susceptible to rot at the growing point as can others in the section, such as D.nindii. Peak flowering is in late winter, 2-3 inflorescences can arise from each pseudobulb. They are gently arching about 40 cm long and producing up to 20 attractive creamy-white flowers with a purple veined labellum.

All my plants are in pots with a basic bark and pebble mix on a 4:1 ratio. Use a size of bark according to the size of the plant. Mature plants do well when the ingredients are roughly 1.5-2cm in diameter and intermediate plants are happy with a 1cm diameter particle. I've not tried this species on slabs as the pseudobulbs at up to 1m would be a bit unmanageable in my small structure.

The species from within Section Latouria exhibit the rich diversity to be found in tropical orchids. From the spectacularly bizarre D.spectabile to the tiny dull D.amphygenyum the section has got it all. Hairy or smooth, full of colour or glistening white, large and showy or small and secretive, there's something for everyone.

One of the more diminutive species is D.aberrans. What it lacks a little in overall size, mature plants are a maximum of 20cm tall, it makes up in the impact of its floral display. An 80mm pot can easily accommodate 25 clavate pseudobulbs (clavate means thin at the bottom and bulbous and round at the top like a club). When it flowers in the late winter or early spring, most of the inflorescences are produced from the new pseudobulbs but some of the older ones will flower as well. The inflorescence is 7cm long, gently arching and bears up to six white, widely opening flowers. Individual flowers are about 2cm wide and last about three weeks. They sometimes have a flush of pale pink accentuated by a bit of pink on the column. This species has a very curious labellum being mostly broader than long with the side lobes much larger than the mid-lobe. The mid-lobe can be deeply dissected giving a very weird effect to the whole flower. A plant in full flower is a very compact but eye-catching exhibit.

There appears to be few cultural difficulties with this species. An 80mm pot is all that is required. I have had best success using seedling grade bark and pebble mix on the 4:1 ratio again. One problem that occurs from time to time is an emerging pseudobulb will dive down into the potting media rather than growing erect. Such a growth can be salvaged by gently teasing it out and up to the proper orientation. This is best done in the warmth of the day as otherwise, the growth can snap off if it is too cold.

Plants over-wintered in the shadehouse seem to slow down in growth a bit and don't flower as well as their glasshouse congeners. The pseudobulbs are smaller and you don't get as many flowers on the raceme.

Cribb (1983) gives the altitudinal range for this species as 300-1900m. Nearly all the plants in cultivation appear to have originated from an early importation from Papua New Guinea by Phil Spence of Bilgola, NSW. Certainly the ones distributed by Deane's, Mackinney's, Wondabah and Florafest have been bred from this stock. The parent plants were collected from Agaun on Mt Duau in the southern portion of the Owen Stanley Range. The altitude was approximately 1800m but the local topography was such that the environment was warmed by exposure to warm air movement from the ocean (P.Spence pers.comm.). Perhaps then, if material of D. aberrans could be sourced from a higher, cooler altitude, a better degree of cold tolerance would be exhibited by the progeny? If your shadehouse environment is better than that that can be obtained in western Sydney this species should certainly be given a go. A cool glasshouse would, I imagine, suit this species quite well as it thrives in my heated structure.

The orchids from the Section Hyalosema within Bulbophyllum have some of the largest individual flowers to be seen in the genus. They are showy plants and certainly attract attention on the show bench. The flowers are produced on solitary inflorescences and are held well clear of the foliage.

In this species the flowers are large, to 7cm long, and are held on an inflorescence that can be up to 15cm tall. The dorsal sepal is large as are the lateral sepals. The dorsal is hooded and nestles down onto the lateral sepals which are joined along the lower margin. The flower is basically a dull white but it is heavily marbled or peppered with brownish or purplish red. The petals are tiny, almost vestigial, and are only barely noticeable next to the column.

In 1989 I obtained my first piece of this species from Ian Walters of Townsville Qld. It arrived established on large chunky bits of charcoal in a wire mesh basket. Over time, moss has established over the charcoal. The B.fritillariiflorum is still in the basket although pendant growths have been pruned from it many times. Some have been readily established on tree-fern totems. It is a vigorous grower so the totem is better cut on the long side rather than square. Try to keep the totem moist at all times although it doesn't seem to mind drying out occasionally if you can't get to the tap for a few days in a row.

It flowers readily under glasshouse conditions, whether hung high in good light or down below under the bench where the light is poorest in the structure. Flowers are produced throughout the year at irregular intervals. A point of interest, summer flowers reach the maximum proportions but flowers produced during the cooler months reach only about 5cm long. Individual flowers last about two weeks.

I wouldn't recommend this species for shadehouse culture in the higher latitudes but it very amenable to warm glasshouse culture.

I hope that these general notes on how I manage my collection and the more specific species accounts stimulates some growers to try some of these more 'exotic species'. They are not hard to grow - the hardest part can be obtaining the stock in the first place. Never-the-less, the New Guinea and Island species are becoming more available and cultivation information is filtering through.

I am very grateful that the ANOS founding fathers were wise enough to include New Guinea and the Pacific Islands within our boundaries. They certainly tripled or quadrupled the range of species that can be enjoyed within our organisation. Look out for the stock, pester people who you think might know a bit, and give the plants a go. Its beyond question that you will be rewarded.

References

Cribb, P.J. (1980). Three new species of Dendrobium Section Ceratobium from Papua New Guinea. The Orchadian Vol.6(8): 174-178.

Cribb, P.J. (1983). A revision of Dendrobium Sect. Latouria (Orchidaceae). Kew Bulletin Vol.38(2): 229-306.

Cribb, P.J. (1986). A revision of Dendrobium Sect. Spatulata (Orchidaceae). Kew Bulletin Vol.41(3): 615-692.

Halle, N. (1977). Flore de la Nouvelle-Caledonie et Dependances, 8: Orchidacees. Museum National d'Histoire Naturelle, Paris.

Kores, P.J. (1989). A precursory study of Fijian Orchids. Allertonia 5(1): 1-222.

Lewis, B.A. & Cribb, P.J. (1989). Orchids of Vanuatu. Royal Botanic Gardens, Kew.

Lewis, B.A. & Cribb, P.J. (1991). Orchids of the Solomon Islands and Bougainville. Royal Botanic Gardens, Kew.

Smedley, D.I. (1992). Cultivation notes on Sarcochilus olivaceus Lindley. The Orchadian Vol.10(7): 227-228.

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