Orchid Basics – Labellums and Columns

Orchids are unique in the floral world. Two distinctive characteristics that set orchids apart from other plants are the labellum and the column.

The labellum is a modified petal.  It is extremely varied in appearance; “often lobed, spurred, adorned with glands, appendages of calli (callus, a hardened swelling or thickening of the skin), sometimes mobile and highly irritable and often brightly coloured”. * The labellum is important for pollination.

The column (as described by Bates and Weber) “is a distinctive feature of all orchids and a unique structure in the plant kingdom. It is formed by fusion of the male parts ‘stamens’ and female organ ‘pistil’.”*

Below are examples of the various types of labellums and columns in some South Australian terrestrial orchids. Each genus has its own characteristic labellum and column.

Sun Orchid
Thelymitra – though the labellum is almost indistinguishable from the other petals and sepals, the column is quite complex.
Hyacinth Orchid
Dipodium or Hyacinth Orchid
Greenhood
Pterostylis or Greenhoods – generally a simple labellum with the column hidden well back into the hood.
Spider Orchid
Arachnorchis (syn Caladenia) can have quite varied and complex, mobile labellums
Helmet Orchid
Corybas or Helmet Orchid – the labellum dominates and the column is hidden deep inside the flower.
Donkey Orchid
Diuris or Donkey Orchid – the labellum is divided giving the appearance of more than one structure.

*Bates and Weber Orchids of South Australia 1990

 

Notes on Dipodium pardalinum at Silverton

A site, along Rarkang Rd, Silverton, leading into Talisker Conservation Park, was visited on December 29, 2012, January 2, 2014, January 16, 2015 and January 9, 2017.

In the earlier years about 20 specimens of Dipodium pardalinum were found with 18 (plus 3 beheaded) in 2015.  A small number of D. roseum was located in 2012, none in 2014, one in 2015 and none at all in 2017.

In 2017 there was bumper crop of D. pardalinum and Ed Lowrey, Helen McKerral and I counted 124 flower spikes.  This may represent only 122 plants because in two instances there were two spikes emerging from one tuber (see image).  It is possible that other closely placed flowers were also growing from a single tuber. This same phenomenon was observed in two cases, with D. roseum, at Hender Reserve, Stirling, on January 12 this year.

All spikes of D. pardalinum this year were found on the verges of Rarkang Road or nearby inside private property in small holdings, with houses, adjoining the road, apart from two spikes only, just inside the Talisker Conservation Park, where Rarkang Road heads into it.

The genus Dipodium is much more varied than I realised.  Our DVD, South Australia’s Native Orchids, only deals with the ‘leafless saprophytes, mycophytes or hemiparasites’.  If you go to ‘Native Orchids of Australia’ (Jones, 2006), you will find that among the terrestrial species there are both leafless species (as with the local D. pardalinum and D. roseum), that are impossible to cultivate and one species with leaves (D. ensifolium), found from Cooktown to Ingham, in Qld.  It is easy to grow in a pot.  Bob Bates told me that it is grown here in Adelaide, preferring a heated glass house, but has been grown successfully in gardens.  And then there is a leaved species, D. pandanum, of limited distribution in Qld, that can be either terrestrial or epiphytic, growing up to 5 m in length.  Old pieces that break off and fall to the ground, nestle in the leaf litter and put out new shoots that eventually climb into the trees.  It is easy to grow in a pot (in the right climate).

Leo Davis.

Dipodium pardalinum.
Rarkang Rd, Silverton, Jan 9, 2017.
 d-pardalinum

 two in one spike.jpg Two spikes of Dipodium pardalinum emerging from one tuber.

Rarkang Rd, Silverton, Jan 9, 2017.

A clump of Dipodum pardalinum spikes with at least two emerging from one tuber; see photo above.

Rarkang Rd, Silverton, Jan 9, 2017.

 Pardalinum spike.jpg

 Roseum and Pardalinum.jpg

Dipodium pardalinum (labellum white with dark pink spots) growing intertwined with D. roseum, (labellum pale pink with dark pink stripes).

Rarkang Rd, Silverton, Dec 29, 2012.

 

Does South Australia Have a Christmas Orchid?

Western Australia has the Christmas Spider Orchid (Caladenia serotina) and the Christmas Leek Orchid (Prasophyllum brownie) whilst in the rainforest of the eastern seaboard is the Christmas Orchid (Calanthe triplicata).

In the disc South Australia’s Native Orchids, 2011, no orchid has the common name of Christmas Orchid but there are several listed that could be a possible candidate.  The ones that springs to mind are from the genus Dipodium.  In South Australia, there are four species flowering at this time:

  • D. campanulatum (Bell Hyacinth Orchid)
  • D. punctatum (Dark Spotted Hyacinth Orchid),
  •  D. roseum (Common Hyacinth Orchid)

    Dipodium roseum
    Dipodium roseum
  • D. pardalinum (Small Spotted Hyacinth Orchid)

    D pardalium Flower and Bud
    Dipodium pardalinum – Note the yellow staining on the bud and no stripes on the labellum

All four are in flower now – D. campanulatum and D. punctatum in the South East and D. roseum and D. pardalinum in the Southern Lofty Ranges.

There have been other orchids which would have flowered over the Christmas period but in recent days we are have been having an increasing number of dry year, especially this year (2015) which has resulted in the orchids flowering earlier.  For example, Prasophyllum murfetii

Prasophyllum murfettii sm
Prasophyllum murfettii (Denzel’s Leek Orchid)

finished flowering in November instead of December and Thelymitra circumsepta

Thelymitra circumsepta
Thelymitra circumsepta (Naked Sun Orchid). This photograph was taken on the 28th December 2010

finished flowering in early December but has been seen in flower soon after Christmas Day.

So does South Australia have a Christmas Orchid?  Until 1991, D. roseum was included under D. punctatum and the common name according to Bates and Weber 1990 was Christmas Orchid.  It seems a pity that when the split was made that neither species retained the common name but nevertheless as they both flower at Christmas, we do have a Christmas Orchid or two!

Reference:

Bates R J, Ed, 2011 South Australia’s Native Orchids, NOSSA

Bates R J & Weber J Z, 1990 Orchids of South Australia

‘Tis the Season … for Dipodium

For many with Christmas and New Year holidays it is a busy time but not so with the orchids here in the Adelaide region.  The vast majority of orchids have finished flowering for the year except for a few including one of our most showy orchids, the Hyacinth Orchids (Dipodium species).  Of the four species found in South Australia, two are found in Adelaide Hills –  D. roseum or Common Hyacinth Orchid and D. pardalinum or Small-spotted Hyacinth Orchid and these will be flowering across the whole of the summer period.

Both of these Dipodium species are leafless plants that are dependent upon mycorrhizal fungi associated with stringy bark trees, either Eucalyptus obliqua or E. baxteri.  This growth requirement makes it impossible to grow in cultivation.  (Stringy bark trees can’t be grown in pots!)  The emerging stem and buds resemble an asparagus shoot.  The stems can range from a light green through to a deep dark red.  At this stage it is difficult to tell the two species apart although if there are yellowing tips on white buds it may be a clue that the plant could be D. pardalinum.

Once in flower D. roseum has a surprising range of variation  from carmine (a lightly purplish deep red) through to pink to white, with suffused rather than clearly defined spots.  On paler or white flowers these blotches may appear pale mauve-pink rather than candy-pink.   It always has a distinctive striped labellum.

Dipodium roseum composite

This feature sets it apart from D. pardalinum which has a clearly spotted labellum and in contrast to D. roseum, the flowers lack variation of colour but are consistently white with small well-defined candy spots.  (There are other Dipodium species with larger spots.)

Note the yellow staining on the bud and no stripes on the labellum
Note the yellow staining on the bud and no stripes on the labellum

And the final word, D. roseum is common but D. pardalinum is rated vulnerable in South Australia.

 

Reference: South Australia’s Native Orchids Bates 2011