Bulbophyllum weinthalii

A BIT ABOUT . . . Bulbophyllum weinthalii

 

© Gerry Walsh

 

 

 

 

 

IT WOULD no doubt surprise a lot of native orchid growers to learn that Bulbophyllum weinthalii has the largest flowers of all the Bulbophyllum species of Australia. It could be argued that B. Iongiflorum, B. baileyi and a few others might have longer, or more spidery segments, but these warmth-loving species have no where near the mass that a nice big bloom of B. weinthalii does. In fact, the best-sized blooms on a plant of B. weinthalii are actually larger than the pseudobulbs of the clump itself. Now that is not a bad effort for a temperate species . . . which are usually belittled by most of those big gaudy tropical things.

 

These magical blooms can get up to 2cms across and the best-shaped flowers are nearly round – there is nothing at all dainty about B. weinthalii. This delightful species escaped detection until 1933, or scientific description at least. This is something of a surprise to me because B. weinthalii is 100 per cent reliant on the Hoop Pine for its survival. Once the mighty Red Cedars were cut over, old time timber getters turned to the Hoop Pine for their harvest. So there must have been a heap of good orchid pickings for the early botanists to dribble over. How could they have missed B. weinthalii?

 

I have not read or heard of it being found on any other tree species but I did find a small clump growing on rock at Dorrigo in 1983. This exception to the rule may have actually fallen from one of the many giant Hoops above in which B. weinthalii was reasonably abundant. Whatever the case, it was certainly well attached to its stone host and had been in position a long time.

 

  1. weinthalii was thought to occur from the Dorrigo Plateau, on the mid-north coast of NSW, up to just over the border into southern Queensland. That was until Denis Johnson and myself found it to be quite common way up in the Calliope Ranges west of Gladstone. This tremendous find extended the range of B. weinthalii by 400 kms. The details were recorded in The Orchadian Journal in 1993. David Jones, the botanist, has raised it to the rank of sub-species striatum.

 

The Hoop Pines on which it makes its home are only found high in the ranges a fair way from the coast. There are a few spots where big Hoops grow at low altitude and close to the coast. Despite supporting a plentiful orchid flora, they never have B. weinthalii on board. And yet, in the ranges, you stand a fair chance of finding it underneath any Hoop Pine that has reached old age. Young Hoop Pines will not play host to B. weinthalii.

 

  1. weinthalii does not form large clumps or sheets, as do some members of the genus. A dozen or so bulbs is the normal size I guess and half of these may be nearly dead and withered. The biggest clump I have seen was found on the slopes high up on Mt Lindesay, which straddles the NSW/Queensland border, at a point a hundred kms from the coast. It was about as big as a dinner plate and grew on a gnarled old burl of a huge Hoop Pine limb. Strangely enough, this was the only plant located on that mountain despite three separate visits over the years. And there are many grand old Hoops in that locality so finding suitable Hoops does not guarantee finding B. weinthalii.

 

Until discovering it up near Gladstone, by far the most likely place to find this orchid was around the Dorrigo area. There are a few spots up there that support good stands of ancient Hoops and whenever I pass through I am always scheming up ways to have a search under them. Usually a piece of B. weinthalii will be found. And it goes without saying that the only method to adopt to find B. weinthalii is to find the Hoop Pine first. Search the ground under it, looking for the bigger old mossy limbs that occasionally crash from way up in the canopy. I have never seen a clump growing anywhere near the ground – even up in the mighty Calliope Range where it can only be described as abundant.

 

Having grown this northern form of B. weinthalii for years now, or ssp striatum, I can make the following observations. Firstly, the northern form has a different looking flower to the type, or southern form. It is more pointed in the sepals and not as well filled in. It has more striping on the basal half of the segments. The sepals reflex far more than the southern form. And it flowers much later, from May to August, than the southern form does in March to April.

 

The big plus for the southern forms is, in my own opinion, they have the more attractive flower . . . or at least the better ones do. They tend to be more rounded and meatier and the background colour tends to be stronger. The northern form is slightly transparent in the background colour.

 

From a horticultural point of view, the northern form is far easier to grow in captivity. It does not suffer the problems that plague the southern form and make it notoriously difficult to grow and flower. With the southern form it is hard to keep leaves on board and even harder to grow fat pseudobulbs on the clump. The initial burst of roots gives false hope to the grower but they soon stop dead in their tracks.

 

If they have attached to a mount they may well separate away. A specimen will maintain itself for a year or so but then it will slide into a downward trend and lose vitality, as well as its leaves. A newly collected plant will flower the first year and maybe the next but you would be pretty lucky to see any blooms beyond that. It just seems that the southern forms of B. weinthalii refuse to put in the effort.

 

Sub-species striatum simply romps away, the bulbs get fatter each year, very few leaves drop off prematurely and they tend to flower their heads off in comparison to the southern ones. And of course having a few pieces to experiment with has enabled me to work out the best way to grow it. Some actions I have taken have been good and others have been useless to say the least. Basically, if you want to grow B. weinthalii well, you must start with the right host.

 

I have tried many hosts over the years and particularly of late. I tried old pieces of hardwood palings and the results were not good. The roots would not stay attached to the spongy surface. Paperbark is no good either. The roots just do not want to attach to it. I have had good results with cork, even that granulated corkboard proved to be a good host. Natural cork was by far the best of course. Once the roots get into a deep damp crevice of cork they tend to lose the ability to attach firmly to it. So use a smooth bit right off.

 

Tree fern fibre proved rather unpredictable to start with. But after some time I was able to pick just which situation the B. weinthalii liked and disliked. For starters, I only use Cyathea fibre, no Dicksonia; its stays too wet. Pieces of B. weinthalii attached to the natural outer layer of the tree fern fibre did not perform well. But pieces attached to sawn blocks romped away. It does not like a spongy damp substrate at all. So I now put it through the saw-bench and remove the outer 2cms of spongy material. Bingo! The roots now cling like glue and the new growths are jumping out of their sheaths.

 

Anyone who has had something to do with Hoop Pine will know two things without doubt. Firstly, the timber will rot away in no time once a tree or limb hits the ground. Secondly, the bark will lie around looking like pipes for years after the wooden centre has rotted. This is what gives this tree its common name, Hoop Pine. The bark is hard and durable, sometimes smooth and sometimes rough, but always forms itself into hoops, from the smallest limb to the widest trunk. It stays hard and almost water repellent for many years before it inevitably collapses. Even the mosses that grow on the limbs are usually the long old man beard types that like it drier. So, applying this knowledge to the bush house situation, it is a logical progression to grow plants on non-spongy surfaces.

 

  1. weinthalii is one species that I believe is worth keeping the fertiliser up to. Those large, fat bulbs and heavy flowers really do need nourishment if they are to perform at their best. While you may be able to get away with a lazy fertiliser regime with a lot of other species, you just cannot get away with it with B. weinthalii. Your only problem will be finding a piece to start with. Hopefully it will soon be available in flask because this is an orchid that seems to set seed pods easily. Flasking has proven to be difficult and no success has been had to date.