Genes, seasonal conditions or pure chance?

Leo Davis is an orchid hunter.  He is meticulous in his observations and notes details that many of us may miss.  In this article he muses upon the variations that he sees in the field.

You, as I do, must occasionally come upon an orchid or an orchid event that is a little outside normal experience.  When I do, I wonder whether this is a purely chance event or is it caused by recent local environmental factors, or is it due to the genes of the plants.  Or a combination of these?

I’ve been watching a couple of patches of fire orchids (Pyrorchis nigricans) that many of you will be familiar with, one at Knott Hill N.F.R., the other at Monarto C.P., where a few plants flower every year, without the normally required stimulation by fire.  I need to check whether it is the same plants that flower each year.

Pyrorchis nigricans.jpg
Pyrorchis nigricans (Fire or Undertaker Orchid) Photo: Leo Davis

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The tall leek orchid (Prasophyllum elatum) puts up leaves at Scott Creek C.P. every year but does not flower. A fire swept through in early 2014 and most plants flowered in October.  They’ve not flowered since.  But over at Ramsay Way, west of Pt. Vincent, a few plants flower each year without fire.  I assume genes are involved.

Prasophyllum elatum
Prasophyllum elatum (Tall Leek Orchid) Photo: Leo Davis

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In April 2014 I chanced upon a patch of Adelaide Hills parson’s bands (Eriochilus collinus), along Moore’s Road, at Morialta C.P., in which the majority of plants had three flowers per stem. Was this because of favourable conditions or genes? Over the next two seasons I saw only the occasional double header and mainly single flowered plants. I will continue observations and records.   

 Eriochilus collinus

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In July 2015 I found a dense patch, about 3 m2 in area, of hundreds the common mallee shell orchid (Diplodium dolichochilum), in Ferries-McDonald C.P. As usual less than ten plants were in flower, but two of them were double headers.  I’ll be checking this season and expect this not to be a chance event but one due to genes.

Diplodium dolichochilum
Diplodium dolichochilum syn. Pterostylis dolichochila (Slim Tongued Shell or Common Mallee Shell Orchid) Photo: Leo Davis

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On May 27, 2012, Bob Bates led a NOSSA outing to Scott Creek C.P. and as ever, when he leads, we saw and learned a lot.  He showed us a patch of fringed hare-orchids (Leporella fimbriata) that he assured us should not be growing there on that steep rocky site and that the plants would not flower most years.  Unfortunately he was right, as usual.   I could not find plants in 2013 and 2014 and it took three searches in 2015 to find a very few leaves. On May 10 this year, over an area of less than 10 m2, I found perhaps 50 leaves and just seven plants in flower.  Three of these had three flowers and a tiny unopened bud (check the photo) and the others were doubles.  I’ve never seen a triple flowered plant in hundreds I’ve seen at Knott Hill N.F.R.  Are genes in an isolated population at play here?  Given the paucity of flowering at this site, it may take me years to sort this one out.

Leporella fimbriata
Leporella fimbriata (Fringed Hare  or Ballerina Orchid) Photo: Leo Davis

Leo Davis.

 

Do Any Orchids Grow Near The Sea?

Orchids are found in a wide range of habitats.  One such habitat is the littoral zone or more simply the seaside.  The following information is taken from the NOSSA’s CD/DVD South Australia’s Native Orchids 2011.

The Littoral Zone

Many orchid species have a linear distribution following the coastline. Here on the leeward side of sandhills the air is usually moist and mild, few frosts occur so close to the sea and sea-fogs in winter will cause water to drip into the sand which easily soaks up both the moisture and the extra nutrients provided by sea-spray. Some of the best known coastal orchids include the gnats Cyrtostylis robusta, pink fairies Caladenia latifolia, coast onion-orchids, Microtis arenaria and coastal helmet orchids Corysanthes expansa as well as C. despectans. All of these are colony forming species, mostly because the windblown sand would soon cover ‘single plant’ species which start to appear after the second line of dunes.

Coastal species can be a few kilometres from the sea but there are several that grow either at the high tide mark, within sight or sound of the sea or in coastal dunes. Apart from the ones already mentioned above, the following are some others that can potentially be found within sight and sound of the sea.

  • Acianthus pusillus (Mosquito Orchid)
  • Arachnorchis cardiochila (Thick Lipped Spider Orchid)
  • Arachnorchis fragrantissima (Scented Spider Orchid)
  • Arachnorchis fuliginosa (Coastal Spider Orchid)
  • Arachnorchis sp Brown Bayonets (Port Lincoln Spider Orchid)
  • Bunochilus flavovirens (Coastal Banded Greenhood)
  • Bunochilus littoralis (Lake Saint Clair Banded Greenhood)
  • Caladenia sp Selfing Coastal Dunes (Little Dune Fingers)
  • Corunastylis nigricans (Port Lincoln Midge Orchid)
  • Diuris orientis (Wallflower Orchid or Bulldogs)

    Diuris orientis
    Diuris orientis (Wallflower Orchid)
  • Diplodium erythroconchum (Red shell Orchid)
  • Glossodia major (Waxlip or Purple Cockatoo Orchid)
  • Leptoceras menziesii (Hare Orchid, Rabbit Ears)

    Leptoceras menziesii (Rabbit Ears Orchid)
    Leptoceras menziesii (Rabbit Ears Orchid) after a fire
  • Prasophyllum elatum (Tall Leek Orchid)
  • Prasophyllum litorale (Vivid Leek Orchid)
  • Prasophyllum sp Late Coastal Dunes
  • Pterostylis cucullata (Leafy Greenhood)
  • Pterostylis curta (Blunt Greenhood)Pterostylis curta Labellum and column 92RL
  • Thelymitra antennifera (Rabbit Ears; Lemon Sun Orchid)07 JB T antennifera sm

Unfortunately, where there has been settlement, it is now unusual to find these species so close to the sea.