Orchids In Remnant Roadside Vegetation

This week’s post written by Leo Davis is an article (slightly edited) from The South Australian Naturalist 91 (1): 34 – 37 January – June 2017. In this article, Leo highlights the importance of  the role of roadside vegetation in preserving the native orchids and flora.

All photographs are by Leo Davis.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 OrcFig 1: Thelymitra antennifera hybrid

One of my rules of thumb is ‘If I am in a Conservation Park, I’m on ground that nobody could make a living from.’ One, usually more, of nutrient poor soils, excess salinity, extreme rockiness, steepness, poor moisture retention, low rainfall or even being waterlogged, will be a feature of the location. There are a few odd spots that have survived partly intact, that have good soil, sufficient rainfall, etc. These include cemeteries (The Nationally Critically Endangered ghost spider orchid (Caladenia (syn. Arachnorchis) intuta) holds on in a cemetery on Yorke Peninsula) or exclusion zones around water storages (including a reservoir reserve in Lobethal that the public can now access) or abandoned railway yards (including Sherlock, where so far I have found 21 species of orchids and part of a reserve in Halbury.)

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 2: Little Yellow Club Mallee Spider Orchid Caladenia (syn Arachnorchisverrucosa

When I go in search of plants with the Botany Group of the FNSSA (Field Naturalist Society of South Australia), or for orchids with NOSSA (Native Orchid Society of South Australia), or when I do surveys of threatened orchid species with DEWNR (Department Environment, Water and Natural Resources), or orchid seed collection with the Adelaide Botanic Gardens, or go on weeding parties to protect endangered species, the destination is always one of these deprived, rejected sites. The orchids I see are those adapted to or just hanging on in such sites. We never see orchids that lived on better soils, say on the Adelaide Plains. How many have become extinct?

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 3: Common Mallee Shell Orchid Pterostylis dolichochila

Wherever the land was suitable for agriculture it was clear felled. Almost nothing of the original flora and little of its associated fauna, were left. But there is a tiny flimsy exception. Crossing these highly productive agricultural zones are roads and sometimes these have remnant vegetation. For a person interested in orchids, these narrow strips are normally areas of slim pickings but occasionally finds are made. Near Halbury, the Nationally Endangered Halbury rufoushood (Pterostylis sp. Halbury or Oligochaetochilus lepidus) can be found in some roadside spots.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 4: Mallee Bearded Greenhood Pterostylis (syn Plumatichilos) sp. Mallee Bearded Greenhood

The most remarkable piece of roadside vegetation that I have come upon was discovered by and shown to me by Glenn Dean, the Environment Officer with the City of Murray Bridge. He found a section of predominantly broombush (Melaleuca uncinata) vegetation, only about 200 m. long, on the verges of a single car sandy track, east of Murray Bridge. It is so close to the vegetation that cars can be scratched. I have found 24 species of orchid (Glenn has found more) blooming there sometime between March and October each year. All images shown here (Figs 1–11) were made at this site. If the little used road was not there the land would have been under crop, being equal in quality to regularly cropped fields to either side, and is of much higher quality than any normally allocated to Conservation Park status. Most of the orchids found can indeed be found in some of the poor sites dedicated as Conservation Parks, including species similar to those found at Ferries McDonald and Monarto Conservation Parks with their poor sandy soils. But this spot, which for some reason supports species that do not grow just 100 metres east or west along the road, has such species as the Nationally Critically Endangered Mallee Leek Orchid (Prasophyllum constrictum) (Fig. 8), that requires soils as good as those demanded by wheat, so it is essentially doomed.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 5: Rusty Rufoushood Pterostylis biseta (syn Oligochaetochilus bisetus)

Its single plant sighting here is regarded as a ‘rediscovery’ of a species not seen for years. In the longer term I guess this tiny site of orchid species richness is in a transitory state and most species will disappear. The surrounding cropping land is neither a source of seed nor a suitable landing site for it and it provides damaging wind blown nutrients and other chemicals. So I will cherish it while it lasts and hope others appear, if only briefly. Here is a reminder, that most of you do not need, of the value of roadside vegetation (with the understanding that it can contribute to native animal mortality) and that we should manage, extend and guard its presence.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 6: Rufoushood Pterostylis (syn Oligochaetochilus) boormanii complex sp.

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 7: Cinnamon Donkey Orchid Diuris palustris

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 8: Mallee Leek Orchid Prasophyllum constrictum

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 9: Limestone Tiny Shell Orchid Pterostylis cycnocephala
(syn Hymenochilus calcicolus)

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig. 10: Caladenia (syn Jonesiopsis) capillata x Pheladenia deformis hybrid

Microsoft Word - SAN Vol. 91, No. 1, Jan-Jun 2017  pp. 34-37 Orc

Fig 11: Small Rustyhood Pterostylis pusilla (syn Oligochaetochilus pusillus)


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2017 June Winning Picture

1706 sm RWL Thelymitra grandiflora 10

This month’s theme for the photo competition was blue and white. White flowers can occur as a result of lack of colour such as Rosalie Lawrence’s Caladenia latifolia (Pink Fairies) which is normally pink. White orchids can also occur naturally such as the Arachnorchis argocalla (White Beauty Spider Orchid) and Arachnorchis intuta (Ghost Spider Orchid) both photographed by John Fennel, or as a dominant colour such as Lorraine Badger’s Eriochilus collinius (syn Eriochilus sp Hills Woodland).

Of the blue orchids, both Ricky Egel and John Badger entered pictures of Thelymitra x truncata (Blue Spotted Hybrid Sun Orchid) whilst Robert Lawrence entered a Thelymitra grandiflora (Giant Sun Orchid) which was the outstanding winning picture.

Blue in the floral world is unusual colour in the floral world for it is not a naturally occurring colour. In fact, “[t}he key ingredient for making blue flowers are the red anthocyanin pigments. Less than 10 percent of the 280,000 species of flowering plants produce blue flowers.” (Lee, 2010 as cited in Oder 2014).

Whilst blue orchids occur outside of Australia, their “colour cannot rival” … “the intensely blue flowers” … “especially [are] unique in the orchid world” … “of their Australian counterparts. The sun orchids (Thelymitra) in particular are famous for their sky blue flowers.” (Ronse 2008: 103)

Based upon Jones 2006 tome, the following genera have true blue orchid species – Cyanicula (9 species), Pheladenia (1 species), Epiblema (1 species) and the largest group Thelymitra (about 65 out of potentially 118 species) plus one hybrid, XGlossodenia tutelata. Of the epiphytes, blue is almost non-existent except for three which Jones lists that rarely might be bluish and they are Vappodes bigibba, V. lithocola and V. phalaenopsis*.

With such rarity, is it any wonder then that the Chinese attached special significance to it as a plant that could cure lung disease and the Aztecs saw it as a symbol of strength.

*Names used as they appear in Jones 2006 tome

Reference

Jones, D. L., A Complete Guide to Native Orchids of Australia Including the Island Territories. Reed New Holland

Lee, David (2010), Nature’s Palette: The Science of Plant Color< Chicago, University of Chicago Press

Oder, T, The Science of Blue Flowers https://www.mnn.com/your-home/organic-farming-gardening/stories/the-science-of-blue-flowers accessed 6 July 2017

Pretty Zesty All About Blue Orchids http://www.prettyzesty.com/2012/11/all-about-blue-orchids.html accessed 6 July 2017