Sarcochilus olivaceus

A BIT ABOUT . . . Sarcochilus olivaceus

© Gerry Walsh

I wrote this article back in 1996. Since then, botanists have beat S. olivaceus up with baseball bats and reshaped the whole species into something a lot different to what it was then. Now it consists of three species, not just S. olivaceus. But I will soldier on and try to convert it into something sensible for the modern era.

If you follow David Jones, there is no longer any orchid called S. olivaceus. The orchid that was formerly known as var. parviflorus from Qld is now given species status as Sarcochilus argochilus.

What us poor orchid growers use to call S. olivaceus is now called S. parviflorus by Jones. So he has shifted var. parviflorus from Qld down to what we have in NSW. In other words, what we used to call S. olivaceus is now S. parviflorus. As I said before; we no longer have an orchid called S. olivaceus. Have I cleared that up? Not bloody likely  I hear you scream. For the sake of simplicity, I am still calling it S. olivaceus, and this is what this article is about . . .

 

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WITH the exception of Sarcochilus falcatusS. olivaceus has the widest distribution of all the Sarcochilus species of Australia. In one form or another, S. olivaceus can be found from the base of Cape York Peninsula in the north, right down to the vicinity of Narooma in southern NSW. Such was the opening paragraph of the original article.

Back in 1996, most growers believed that there were three distinct forms of S. olivaceus. Today, these forms have been made into species in there own right. I for one think this change is good and it is easy to understand the reasons behind the changes.

There is the southern or type form found in coastal ranges of NSW, and the variety borealis, which is the north Queensland form. Variety borealis is pretty well accepted as extending from the Mt Windsor Tableland, southwest of Cooktown, then southwards to around Townsville.

Jones has given this orchid species status as Sarcochilus borealis. The further south you go, the muddier the S. olivaceus complex becomes until you come up for air in NSW. It is the NSW form that this article deals with.

Most growers are very familiar with the NSW form of S. olivaceus and it really needs no introduction. S. borealis occurs only at the highest elevations of its range and usually in rainforest and very often near creeks. It differs in a number of ways, both vegetatively and florally. Firstly, it is a much smaller plant than the southern form, rarely, if ever, having more than 3 or 4 leaves of no more than 6 cms length. These are nearly always thin and papery. The flowers are smaller, much more frail and have more red striping as well. They do not often have more than 6 flowers or so on each raceme.

I have never seriously grown this wet tropics form. I have seen it in the wild, it certainly seems different and I for one am glad that it is now given species status as Sarcochilus borealis. The epithet, “borealis”  literally translates as “northern”.  In the Eungella Ranges inland of Mackay, there grows a form of S. olivaceus. I have not grown it and am not certain at all which form it is. Who can help me on this matter?

The southern form on the other hand can achieve much grander proportions. Occasional plants are real monsters with up to eight leaves of around 12 cms length and up to 4 cms in width. They are generally thin in texture, but occasionally become plumpish and leathery with age. The racemes of the southern form can grow to 15 or so cms and support up to twenty 2.5 cm wide flowers, but this is exceptional and six to a dozen would be more the norm.

Don Barnham grew a plant in his bush house, in about 1985 that had the longest racemes of any specimen of S. olivaceus I have ever seen – either in the wild or in collections. I remember counting the swollen buds and arriving at the figure of 19. I regret to this day never having seen that whopper once it opened. The moral of the story is simply this: S. olivaceus occasionally grows to gargantuan proportions. It is rather similar to S. australis in this regard.

The blooms of S. olivaceus are generally a soft light green in colour. Occasional forms will have lime green flowers and some others tend towards a yellowy colour – sort of like the inside of an avocado. The chin of the labellum is quite square and proportionately oversized when compared to the rest of the flower. There is distinct red/brown barring across the chin. The colour effect is quite pleasing.

But there is another form of S. olivaceus to be seen in the Australian bush. It occurs from roughly the Qld border up to at least as far north as the Calliope Range near Gladstone. Lindley named it Sarcochilus parviflorus in 1838 but this was not generally accepted because the name fell into disuse. More recently Clements and Dockrill in their respective publications have reverted back to the species concept. Dockrill at least expresses some timidness in doing so.

This form differs from the type form in many ways and when I first saw a specimen in flower I had no idea what I had found. It looks very different to the type form in most regards. For starters, the labellum mid lobe is solid white, not opaquely green/yellow as in the type form. The side lobes are very noticeably forward projecting as well. The whole flower is thinner in the segments and slightly smaller, giving a crabbier appearance. Also, at least in my bush house, it flowers later than the type variety.

Within the range, S. parviflorus is quite a variable species, particularly up in the Calliope Ranges west of Gladstone. The biggest variation would seem to be in its overall colour, which can vary from yellow tones through to light brown, tan and several shades of light green. But never the lime green of some NSW plants of S. olivaceus.

I remember exploring an extensive colony of this S. parviflorus in southern   Queensland in about 1997. It was growing amongst other Sarcanthinae species such as S. hillii, S. dilatatus and Rhinerrhiza divitiflora. There were a large number of S. weinthalii specimens to be seen as well. All these species are indicative of dry rainforest environs.

The most obvious difference I noticed was just where this form chose to grow; mostly on the outer twigs of this shrubby, dry rainforest. Its roots were highly aerialised in the manner of Plectorrhiza tridentata, only there was, surprisingly, none of that species to be seen in this spot. This is in complete contradiction to the habit of the type form of S. olivaceus.

The type form nearly always selects the major limbs and trunk of its host and only occurs incidentally on the twiggy ends of limbs. As well, I cannot think of a single location where S. olivaceus grows that Plectorrhiza does not grow with it. Plectorrhiza will grow without the presence of S. olivaceus though.

This var. parviflorus differs from the habit of the type form of S. olivaceus in another major way. Whereas the type form is rarely found any distance from water S. parviflorus chooses the opposite. Most of the considerable numbers of specimens I have seen were way up a hillside a long way from a dry watercourse. They were doing it tough in the midst of other species that are noted for their preference for harsher conditions. As well as the Sarcanthinae species mentioned, there were also numerous specimens of Dendrobium speciosumD. teretifolium, D. monophyllum and D. bowmanii. All of these tend to avoid the shady, damp recesses where the type form of S. olivaceus eagerly colonises.

Considering all the ways in which S. parviflorus differs from S. olivaceus, (colour, shape, distribution, habitat and positioning on its hosts – is there much else?) it is not surprising to see that most enthusiasts and professionals now see Sarcochilus parviflorus as a true species. The only similarity between the two is perhaps the vegetative features of the leaves. These tend to be thin and wafery compared to other Sarcochilus species.

  1. olivaceus,as I have mentioned, prefers the coolness of a mountain creek to exposed ridges or the canopy of the rainforest. It frequently colonises the Water Gums(Tristaniopsis) along such creeks. It is also at home on the Myrtles (Backhousia) that inhabit the belt of trees just behind the Water Gums. In some areas to the south of Sydney, huge plants can be seen on the bottom metre of the trunks of these Myrtles. Such positions are not bright enough for most orchid species but S. olivaceus, with its ability to produce extra wide leaves, can gather enough light down there to satisfy its needs.

Further south into the Illawarra S. olivaceus can be seen growing on rocks, usually with quite long roots. Up in the Blue Mountains I know of a good colony growing on bucket-sized rocks on the floor of the rainforest. It does not take long for the roots to descend into the leaf litter. These plants seem to maintain vigour under these unusual damp and dark conditions.

More so than with other Sarcanthinae orchids, S. olivaceus is capable of growing very long roots in captivity. For this reason it is beneficial to attach specimens to long mounts . . . and long lasting mounts at that. As the roots keep snaking around the mount they quickly form a maze and any attempt to remount a long established S. olivaceus plant would mean damaging the root system far more then with other Sarcs.

This species is subject to, like most Sarcanthinae species, that dreaded crown rot that can decimate a seemingly healthy plant in just a few days. Years ago I christened this condition SSDS: Southern Sarc Death Syndrome. Anyone who has grown a mixed collection of epiphytic Sarcs will know exactly what SSDS is. It generally means the death of the plant but it can, on rare occasions, lead to better things.

This happened to a superb form of mine that had won me more prizes over the years than nearly any other orchid in my collection. But the good news is that, although the plant looked completely done in, the roots remained healthy. After six months of hibernation, three kikis began growing from the old rhizome. This clump reached full size again but with the added bonus of three separate growing leads. After 12 years of successful cultivation, SSDS eventually claimed it. Such is the tale for nearly every twig epiphyte.

Here is a species that I prefer to grow on cork, and long lengths of it. Most other materials will suffice however, but I do not advocate the use of tree fern fibre, which I tend to use with a lot of our native orchids. It is difficult to cut tree fern into long narrow strips and even if you do they tend to collapse in short time.

  1. olivaceusis a species that I try and give much more water to then others within theSarcanthinae. I actually keep a small hand pump spray container of water next to my best plants. I also keep some weak fertiliser and some fungicide in it. I will spray this on a few chosen Sarc. species whenever I pass. Do not be fooled however, I still get SSDS with annoying regularity. I manage to feel warm and fuzzy for trying however.

The good news for novice growers is that S. olivaceus is quite an abundant species in the bush houses of Australia and you should have no trouble picking up a plant for yourself. It is a rewarding, showy species And it never fails to flower each and every spring. As an added bonus, the perfume of S. olivaceus is both potent and sweet. Grow it and enjoy it . . . it sure is a gem.