Sarcochilus dilatatus

A BIT ABOUT . . . Sarcochilus dilatatus

© Gerry Walsh

Two colour forms of Sarcochilus dilatatus

Sarcochilus dilatatus is something of a mystery species to most native orchid growers. Everyone knows what it looks like and they can tell you how it influences the hybrids in which it is a parent. But not a whole lot of growers have seen S. dilatatus in the wild and even less have much idea about the conditions it likes to hang out in. Most will also support the notion that S. dilatatus is difficult to grow in captivity There isn’t a whole lot of specimens to be found around the bush houses in the village of Sydney, or in any other village really. These hazy ideas, held by the majority of growers, are quite natural and it is easy to understand just how the vagueness that surrounds S. dilatatus has evolved.

The first plants of S. dilatatus that I ever seen were seedlings which were distributed from flasks at a meeting of ANOS Sydney Group some time in 1983. I obtained four of these and promptly killed them before ever seeing any flowers. The next plants I experienced were shown to me in September 1987 by the late Ralph Crane, from Brisbane, and were growing in the Brisbane Forest State Park. I’ll never forget the elation of that first glimpse of these wild growing plants. And I quickly understood just how I’d murdered those precious seedlings back in ’83.

As is often the case, seeing those first wild plants of  S. dilatatus gave me all the understanding I needed to successfully grow this small Sarcanthinae species. Little did I realise that S. dilatatus would prefer to grow on the thin twigs of shrubs in a small, dry, Lantana-choked gully, much more than on the thick moss-encrusted slab of hardwood where I had sentenced those seedlings to a slow death. There can be no disputing the value of studying the habitats of the various native orchid species we come across. Far too many growers go all dribbly at the mouth at the sight of a nice orchid growing in a tree, but fail to observe where the tree itself is growing.

I tend to think of S. dilatatus as a sort of northern form of S. australis. They both grow in almost identical situations with regards to position on the host, air movement, moisture and light. They even have a floral shape vaguely similar i.e. long and narrow with club like ends to the segments. It is quite possible that these two species have a common ancestry.

  1. dilatatus is very uncommon in NSW. I have never seen a plant growing in situ in the wilds of my own state. It certainly exists sparingly in dry scrubs away from the coast and to the west of about Grafton. I have no real knowledge of it occurring elsewhere in NSW.

North of the border, S. dilatatus begins to appear with regularity. As mentioned above, the preferred habitat appears to be dry, scrubby rainforest and creek beds, noticeably at low to moderate altitudes and at some distance from the coast. By far the greatest number of plants I know of occur in plantation hoop pines in the Sunshine Coast and Noosa Hinterland. It frequently colonises the lower limbs of the older plantings . . . as do a host of other native orchids.

I first observed this feature of plantation hoop pines back in November 1989. On a subsequent visit to these areas in January 1993 I set out to check out as much of this man made habitat as I could in one day. l finished the day having logged in 600 kms and with the view that S. dilatatus is benefiting greatly from the activities of the forest industry in southern Queensland. I could never forget the sight of a dozen or so of the hugest specimen plants of this species that I have ever come across, sitting smugly about four metres above my head. Several of these were hanging off dead limbs.

One in particular supported seventeen leaves and over fifty old racemes. As well, there were eleven new racemes nearly ready to burst into bloom. The plant was on its last legs when collected and unfortunately it never recovered. l kept the dead trophy for years to show all the sceptics just how huge S. dilatatus can get.

I was shocked when visiting the same locale in January 1995, to found about twenty hectares of ploughed up clay and not a stick of shade for hundreds of metres around. It resembled a bombing range. I agree with the need for a forest industry based on plantations but I don’t know how to deal with the idea of letting thousands of orchids perish in the rubble piles after the inevitable harvesting takes place. It makes sense that any plants growing in such forest coups should be rescued before they are killed . . . regardless of how rare or how common a species they are.

A discussion on  S. dilatatus   could not be concluded without mentioning the form that occurs up near Gladstone and at points further inland and up into the Calliope Range. This form of the species first came to my attention when I journeyed up there in September 1992. We found this little  Sarc   that had just finished flowering by a matter of days. For the life of us we could not decide what species it was. What would be flowering in the middle of winter?

The southern Queensland form of S. dilatatus blooms from November through to January i.e. summer. So although these new plants looked like S. dilatatus, we discounted the idea because of this six month discrepancy in the flowering time. After all, it is only four hours car drive to the north of the type range.

Of course, it is now well known that this ponderous species is indeed S. dilatatus, but with a very different habit and appearance. The flowers are much dumpier or stout, being only about one cm high compared to southern flowers which can reach 2.5 cms deep. The colour is the other outstanding feature of these Gladstone plants. The club-like ends of the segments are strongly cerise/ochre brown in nearly all the specimens I’ve seen in flower, while the southern colour varies from yellow through to coffee brown and as dark as treacle brown. A large specimen in full bloom is absolutely stunning.

  1. dilatatus can get up to a dozen buds on each raceme. But this doesn’t mean that there will be a dozen open flowers at any given time. It is the habit of S. dilatatus to open progressively, but certainly not regularly. While two flowers may be open today, these might wilt away after a few days. It could be up to ten days or so before the next one or two buds open. This irregularity means that a specimen plant can have flowers on board for a long period of time. If the weather is not too hot or changeable, each flower can last up to two weeks.

For its size  S. dilatatus usually has an above average number of racemes. A plant with only 3 leaves often has two or three racemes. All this irregularity means that hybrids made with S. dilatatus usually have the same unpredictable flowering habit and blooms can open up over an extended period compared to other Sarcanthinae hybrids.

If you want to grow S.  dilatatus successfully you must consider where it grows in nature and transfer that knowledge across to the bush house. The big choice you must make is what host to tie your plants on to. My favourite host at the moment is two cm thick branches, about forty cms long, of that very common Leptospermum species that has to be nearly the most common tree on the dry ridge tops of the Hawkesbury Sandstone regions. As you can probably gather, I don’t remember what species it is. But it’s the one with the wide and thin flaky bark that peels away in masses when pulled even slightly. This bark is usually a grey colour with just a hint of purple. Do you know the one I mean?

The roots get under this bark and it is very hard to overwater them. This saves many a plant of S. dilatatus and the other quick-die species such as S. australis. In fact I’ve got several specimens of S. australis still growing happily on this Leptospermum host after more than five years. I attribute this success solely to the dryness that the roots find under the copious layers of this ti-tree bark. You virtually can’t wet them unless you set out to do so. Of course it helps to hang them up in some corner where you don’t water them anyway. S. dilatatus is one of those species best hung up and forgotten.

Speaking of roots, those of S. dilatatus are perhaps the most active of all the Sarcochilus species. They are constantly growing – I doubt there is a time in the year when they don’t have long green tips probing their way along through the fissures and layers of bark. I’ve seen wild plants of fairly small size with just a few roots but a couple of them can be pushing a metre in length without any doubt.

Wild plants often carry a great number of seed pods. More than once I’ve observed plants with 6 or 8 pods from last season still not split despite this year’s blooms just opening. To me these pods are just as interesting as the flowers themselves. They represent vigour and fertility that is often absent from some other species of native orchids. For the novice grower, specimen plants of S. dilatatus are just not available. Hopefully it will be available more frequently in flasks in the future. It sure deserves to be.