I FIND Dendrobium monophyllum to be a frustrating native orchid. Perhaps frustrating is not the correct word . . . maybe annoying is more suitable, or it could be disappointing. It’s not that I have any trouble growing this delightful looking species – for it is not a difficult subject for cultivation at all – and it is certainly one of our more attractive orchids vegetatively speaking. What could be as impressive as lots of those stout, conical pseudobulbs all standing to attention in perfect columns, and topped with that singular bright green leaf which is forever erect.
It has the poetic common name of Lily of the Valley Orchid. What I find so irritating has to do with the flowers. Right from the time the emerging raceme sneaks its first glimpse at the roof of your bush house, right up to the moment the first bud bares its soul to the big bad world, D. monophyllum promises great things. The racemes often grow quickly and with great vigour and the closely packed buds crowd onto what always promises to be a wonderful erect spike habit.
But when the first blooms finally decide to open . . . they don’t! They sort of split a bit, occasional plants will actually half open their flowers, but they inevitably leave me suspecting that they really could do far better. Quite often the blooms hang weakly off the rachis – even if the raceme is completely erect. I always have it in my mind that if I could design the perfect D. monophyllum, its flowers would face upwards to the sky. I’d ensure that they opened up to at least half flat. That’s all it would take to make D. monophyllum one of our truly superb native orchids.
It already boasts the yellowest of all the yellow flowered orchids we have in Australia. And the perfume is so powerful on a warm day that you could actually get high on it. If only the beggar would open up and face its admirers . . . but I guess D. monophyllum is not too concerned about pleasing us Homo sapiens. It only needs to impress its pollinator. And if that means evolving its flowers into drooping, cuppy little things, then I guess it’s none of my business. Still, I can dream can’t I?
The very best forms of D. momophyllum do actually manage to hold their flowers in a horizontal mode, without actually facing upwards, but such plants are far and few between. Racemes usually range from 5 cms to around 12 cms long. Occasionally you may see a giant up to 16 cms long. That’s the estimated length of the old raceme on a small piece of D. monophyllum that Mike Harrison and myself saw in a nursery way back in 1983.
It lay among a couple of clumps of this species and as we sorted through the pile we each noticed it simultaneously. I of course remained the perfect gentleman and allowed him to claim it with all the speed of a striking cobra. Unfortunately, he has not been able to get the spikes to that length again during the intervening years. I bet I could have if I had been a bit quicker – or less gentlemanly that is.
The raceme is usually erect but on the really crook forms of D. monophyllum they may actually be slightly drooping. The number of flowers varies not only with the raceme length but also with the flower spacing, which can be either wide or closely packed. I wouldn’t think that you’d ever see more than 20 flowers on D. monophyllum racemes. The flowers would be lucky to exceed 10 mms and most would fall in the 6-8 mm range.
Flowering season is a real toss-up. If your clump is a decent size you may have a flower or two all year round and I certainly have a few plants like this. The real peak would be from November through to December however.
Another burst could occur in the Autumn. If the weather is kind to you the flowers could last up to a month, but in hot weather they may last less than 4 days. In winter, they may just remain as big fat buds for several weeks and may never really open at all. It is possible to get all the blooms on a raceme open at the one time but it is more likely that the basal flowers will wilt long before the apical bud has opened.
D. monophyllum is distributed from just east of Grafton (Clarence River) NSW, all the way up to the Mt Windsor Tableland (south west of Cooktown). Although it can certainly be observed in NSW, it is far more commonly encountered in Queensland. I had searched for it for many years before finally seeing my first NSW plants in 1988. That was in a location surprisingly close to a main asphalt arterial road in the Tweed Valley. There was uncountable tonnes of D. kingianum on this rock outcrop but only a few square metres of D. monophyllum. To this day I still haven’t seen it anywhere else in NSW.
As soon as you cross the border going north, sightings become far more frequent. By the time you reach the Tropic of Capricorn, D. monophyllum becomes a very dominant orchid in the higher ranges away from the coast. Now I know I’m always boring people to death with my ravings about the Calliope Range near Gladstone – but what else can I say? Facts are facts! There are clumps up there, and lots of them, that would cover a billiard table. I’ve also seen it up on the Atherton Tableland near Cairns. It doesn’t seem to form clumps at all up there. Long strands of a dozen or so very robust pseudobulbs are the norm for that part of the world. Even so, it is quite a common species in many of the higher regions of the Atherton Tableland.
While D. monophyllum is happy to colonise both trees and rock face, my observations suggest that it is far more common on the latter. There are spots in the Brisbane Forest Park where it eagerly colonises some of the unfriendliest looking cliffs that one could imagine. Clumps up to a metre across are both healthy and abundant. Although the D. kingianum of this location is extremely prevalent, it refuses to colonise the harsh, hot outcrops where D. monophyllum appears to be most at home. And D. kingianum can be seen in some pretty inhospitable spots as everyone knows. I reckon D. monophyllum may be able to survive in conditions far harsher than nearly any other species of native epiphytic orchid could cope with.
As a tree dweller, D. monophyllum is mostly seen high up on the emergent limbs of the rainforest canopy or in low, stunted dry scrubs a fair distance from the coast. I recall areas on the western end of the Jimna Range where great clumps of it were crowding the exposed upper limbs of very tail trees. Massive clumps of D. speciosum var. grandiflorum and D. teretifolium were highly visible on the same limbs . . . what a sight! Further west, the low-roofed dry scrubs shelter similar displays of D. monophyllum.
These low scrubs are very interesting spots to see orchids. At a most surprising dry gully on the edge of the Darling Downs there is an extensive area of this low scrub terrain that supports many species of native orchids, including some of the rarer ones such as Sarcochilus weinthalii. I’ll never forget the sight of those arm-thick tree trunks, only five or six metres tall, edged in long chains of D. monophyllum stretching from ground level up to the thin branches above. It looks odd, but not near as odd as huge clumps of D. speciosum var. hillii perched in the same under-strength host trees at only two metres above the ground.
The common link in all the sightings I’ve mentioned is high light levels. In fact, D. monophyllum has a serious preference for what virtually amounts to full sun for at least half of the day. And the lesson to be learnt from this is, quite logically, don’t hang your plants down in the gloom under the benches or along the shady side of your garage where the sun never shines. If you’re lucky enough to live in a locale where Old Jack Frost doesn’t inflict himself on you, you should be hanging your D. monophyllum up in the trees around your backyard . . . give them the barest minimum of shade. It is only then that you’ll grow fat, tough pseudobulbs and flower them to their full potential.
Selecting a host for D. monophyllum presents something of a problem. This is not a species that can be tied on to a little piece of cork or fence paling and then forgotten. The more robust clones grow with gun-barrel straightness up or across their hosts. A long mount is mandatory, otherwise the new growth will shoot off into the thin air and form a witches broom effect. Some growers may prefer this appearance. I’d prefer to see a more organised specimen and for this reason my bigger display plants are mounted on logs of Cyathea tree fern fibre. These are complete rounds and not just slabs. The new growth is able to circle around in a never ending fashion and the effect is quite pleasing.
If you can’t get tree fern fibre, the next best thing is old hardwood. I’ve successfully used a metre-long piece of 4×4 hardwood fence post. Again, this allows the D. monophyllum to circle its way around the host. I’ve never had the need to use any other substrates but I should imagine that nearly any material would be suitable, so long as it has the necessary length. The roots of D. monophyllum cling with great tenacity and once established they resent unnecessary interference. So make your mount a long lasting one of suitable dimension right from the beginning.
In the wild, D. monophyllum can form distinctive layers of overlapping bulbs. On really old clumps, there often develops a mass of leafless backbulbs that do nothing to enhance the visual properties of the clump. The good news is that, with selective back-cutting, new life can be urged from seemingly dormant vegetation. So don’t cut off any firm, leafless backbulbs unless you are convinced they are truly beyond resurrection. Back cutting often encourages a burst of flowering from old bulbs as well. So it pays to spend time getting acquainted with your plants.
About the only problem that D. monophyllum seems to be susceptible to is premature die-back and spotting of the leaves. Even young, succulent leaves succumb to this condition and it really can disfigure a specimen plant badly if the problem gets out of hand. I’m not certain what the problem is exactly, but I would guess that a fungus is the culprit. So the regular application of any of the broad spectrum fungicides would probably pay dividends. Wet, humid summer conditions must obviously contribute greatly to the problem. If your plants are only moderately affected by this problem then it could be best to put up with it rather than start spraying poisons all over the place.
D. monophyllum is a species that I suggest you fertilise heavily. It is a robust species that must have a steady supply of nutrients at its beck and call. It resents being wet in winter, and even in the summer time, don’t be tempted to hose it down every day. Remember D. monophyllum likes to do it tough. Keep up the high light levels and give it a feed and there is no reason in the world why your plants shouldn’t give you years and years of enjoyment.