Mass flowering of Corymborkis corymbis Thouars in Dlinza Forest Nature Reserve
Sharon Louw
Ezemvelo KwaZulu-Natal Wildlife, P.O. Box 13053, Cascades, 3202, South Africa.
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| Corymborkis corymbis in full flower |
Years of field work in the Eastern Coastal Scarp Forests of Zululand have made it possible to identify and record sightings of the terrestrial orchid Corymborkis corymbis. I have always been envious of Geoff Nichols’ photo of a flowering C. corymbis orchid in Pooley’s A Field Guide to Wild Flowers of KwaZulu-Natal and the Eastern Region and more recently photos taken by Herbert Stӓrker in Orchids of South Africa, A Field Guide, that captured flowering orchids at Umtamvuna and Port Shepstone. Until recently I had only ever seen these orchids growing in a vegetative state!
The species’ conservation status is currently listed as Least Concern. The literature provides an accurate species description: C. corymbis is a thin-stemmed, somewhat straggling and bamboo-like, semi-woody, evergreen terrestrial orchid that grows up to 1 m tall in deep shade of dense forest, from sea level to 700 m above sea level. In South Africa, scattered localities occur from the Eastern Cape to KwaZulu-Natal as well as one on the Swaziland-Mpumalanga border. The species is widespread in Tropical Africa, Madagascar and Reunion Island. The leaves are spirally arranged along the stem, deep glossy green, elliptic, and pleated with prominent veins. The inflorescence is lax, up to 70 mm long and there are 5 to 15 flower spikes. The flowers are cream to greenish-white, star-shaped, fading to orange. Flowering occurs from November through to February. The flowers are mostly terminal, erect or drooping. The sepals and petals are similar, linear to spatula-shaped, 45–90 × 2–5 mm; the lip is similar but broadens to 5–13 mm near the apex.
While conducting the Endangered Spotted Ground-thrush (Geokichla guttata) nest monitoring during the 2020/21 breeding season in Dlinza Forest Nature Reserve, I stumbled upon a single C. corymbis orchid that showed signs of early bud development! Dlinza Forest Nature Reserve is managed by Ezemvelo KZN Wildlife, covering 319 ha and located in the middle of Eshowe. C. corymbis are randomly distributed throughout the forest and seldom found in large numbers. Conducting a quick search outside the monitoring transect, a large ‘colony’ of C. corymbis orchids were identified and recorded on either side of the Woodcutter’s Trail. The locations of a total of 25 orchids were recorded using a GPS. Orchids ranged in height from seedlings (<80 mm) to tall orchids up to 730 mm. The weekly Spotted Ground-thrush monitoring allowed me to keep an eye on the C. corymbis developments. Soon many more orchids started to produce flower buds. What a sight to finally observe 18 flowering orchids!
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| Early bud development 27 November 2020 |
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| Most plants in bud, 21 January 2021 |
In summary, the first early flower bud development was observed on 27 November 2021, early flowering occurred in a few orchids from mid-January but most flower buds were still closed. Depending on the number of flowering spikes produced, the opening of flower buds was staggered until the end of January. Peak flowering occurred at the end of January through to the first week in February. Early seed set was observed in mid-February in the early flowering orchids. I last observed the orchids on 19 June 2021, seed set had occurred in only six orchids, with one or two seed pods per orchid although one orchid produced five seed pods. Is this the result of poor pollination effort or is the production of millions of spores in a few seed pods sufficient for the species’ persistence? Thus far, flowering orchids have invested eight months in seed production and the pods are not yet fully mature. Thinking back to all the times I have observed C. corymbis, and this being the first time I have observed them in flower, it would seem that environmental triggers, possibly habitat specific, may be responsible for a mass flowering event of this nature.
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| Early flowering, 21 January 2021 |
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| 5 February 2021 |
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| Peak flowering, 30 January 2021 |
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| Seed pod development, 23 February 2021 |
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| Seed pod development, 10 March 2021 |
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| Maturing seed pod, 19 June 2021 |
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| Ripe seed pods splitting to discharge seeds, 22 July 2021 |
Acknowledgements
Ezemvelo KZN Wildlife Field Rangers and General Assistants based at Dlinza Forest Nature Reserve who assisted with field monitoring. Andre Louw, my husband, who happily accompanies me on field trips and particularly so as not to miss C. corymbis in flower.
References
MCMURTRY, D., GROBLER, L., GROBLER, J. & BURNS, S. (2008) Field Guide to the Orchids of Northern South Africa and Swaziland. Umdaus Press, Hatfield, South Africa.
POOLEY, E. (1998) A Field Guide to Wild Flowers KwaZulu-Natal and the Eastern Region. Flora and Fauna Publications Trust, Durban, South Africa.
JOHNSON, S. & BYTEBIER, B. (2015) Orchids of South Africa, A Field Guide. Struik Nature, Cape Town, South Africa.
VICTOR, J.E., MCMURTRY, D., GROBLER, L. & BURNS, S. (2005) Corymborkis corymbis Thouars. National Assessment: Red List of South African Plants version 2020.1. Accessed on 2021/06/24
About the author: Sharon is Ezemvelo KZN Wildlife’s District Ecologist Central East, based in Mtunzini and is responsible for the King Cetshwayo and iLembe Municipal Districts. Part of the Ecological Advice East Division, Sharon provides ecological advice support to Protected Area and District Conservation Managers, co-ordinates and manages several monitoring programmes and is an Environmental Management Inspector (EMI-Level 2). Sharon is passionate about her work, has a wide range of interests, including plants and animals and how they fit into their habitats.
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