In the past week there has been some Facebook conversation on the identification of some Thelymitra (Sun Orchids) here in South Australia. Sun Orchids can be problematic particularly when there is only one photograph. If the photograph has a clear view of a diagnostic feature, then identification becomes simpler but there are many species for which careful observations are necessary to determine the correct one. This is important when considering some of the complexes, eg T. nuda and T. pauciflora which have several similar species. Colour is not always helpful as there can be either variation in colour or no colour at all. Further complicating identification is that Sun Orchids readily hybridise, far too easily sometimes!
When Robert Lawrence wrote his book, Start With the Leaves, he realised the difficulty in identifying some orchids, so he included a checklist of observations. The checklist is extensive but was developed to be used with the electronic version of South Australia’s Native Orchids by RJ Bates which covered all the known South Australian orchids in 2011.
To assist in orchid identification, take as many photographs as possible, showing different parts of the plant and habitat from as many different angles. But remember, photograph the typical plants.
At the bottom of the post is a picture showing the parts of the flower.
The following extract is from pages 185 – 187
Thelymitra species (Sun Orchids)
Describe the habitat where the plants are found
Is the species confined to swamps or very moist sites?
Was the site burnt in the last year or two? (Find out when if possible)
Are the plants restricted to a particular habitat or is there a range of situations where it grows?
Has it multiplied following disturbance?
Does it prefer wet or dry sites?
What other plants are growing with the orchids, including the trees forming the canopy?
Number of plants
Estimate the number of plants or describe the distribution of the plants at the site
Do plants occur in small clumps?
Do plants occur in colonies and if so how large are they?
Size of the plant
What is the height of the flower stem and width of the flower stem?
What are the length, width and shape of the leaf?
Is the leaf flat, channelled (u-shaped) or tubular in section?
Does the leaf change shape along its length?
Does the leaf have parallel ridges?
Is the leaf thick and fleshy or thin and papery?
What colour is the leaf?
Does the leaf have a reddish base and is the red colouration in parallel lines?
Are there any hairs on the leaf and are they confined to the margins?
Is the leaf rigid and upright or is it weak at the tip and falling under its own weight?
What is the tip of the leaf like and does it have a pointed apex?
Are the leaves shiny or to they have a powdery covering?
What is the diameter of the stem?
What is the colour of the stem?
How high is the fistula, the point the point where the stem separates from the leaf?
(Bracts are leaf-like structures along the flowering stem)
How many bracts are there on the stem (ie those that are not immediately below a flower)?
How long is each of these bracts?
What colour are the bracts?
Are the bracts tightly or loosely wrap around the stem?
(Fertile bracts are leaf-like structures at the base of each flower)
How long are the bracts?
What colour are the bracts?
(The ovary is the structure immediately below the petals and sepals that becomes the seed capsule after the flowers are pollinated)
What colour are the ovaries?
How long are the ovaries?
How wide are the ovaries?
What time of the year are the flowers open
What is the length and width of each flower?
Do the petals and sepals open widely, or does the flower remain almost closed?
What colour are the petals and sepals?
Do the petals have spots or darker coloured veins?
Is the labellum larger or smaller than the other segments (petals and sepals)?
Are segments rounded, pointed or cup shaped?
What colour is the outside of the buds?
What conditions are required for the flowers to open? Are they only open in hot, humid conditions?
What colour is the main part of the column?
Describe the post-anther/mid-column lobe
Is there a tubular structure on the top of the column? What colour is this and does it have a collar of a different colour?
Does the lobe have a cleft in the apex and how deep is this?
Does the column have lateral lobes (arms) reaching in front of the column?
Are there trichomes (hair-like structures) in a mop or toothbrush arrangement?
Is there a sharp bend in the column arms?
If there is not a tubular lobe, are there three levels of structures on the column?
Are there papillae (rows of narrow bumps)? How many and what colour are they?
What colour is the crest, if present?
Describe the fragrance of the flower or whether there is none
November 2015 Winning Picture includes T. x truncata and T. x irregularis
Those Blue Orchids Again – An Overview of the Thelymitra nuda complex