PlantLife Volume 56.3, December 2023. Arboreta in South Africa

 

South Africa’s arboreta 

by Michael Cheek

Arboreta and botanic gardens are valuable sites for conservation, education and botanical research as well as sites of beauty and relaxation. In South Africa the first arboretum was established in 1845, but arboretum research truly started with the forestry trials using introduced timber species across the country. Not all of these arboreta have survived to the present day and those remaining have a high value as sites for recreation, conservation and for biosecurity research into the future.

An arboretum can be defined as a documented or labelled collection of living woody plants cultivated for research, conservation, education and display (Cheek & Procheş 2022). There are nice distinctions among arboreta such as a Pinetum, which is a collection of Pine trees, and a Palmetum would be dedicated to Palm species. Examples of South African arboreta with noteworthy conifer collections are Benvie Gardens in the KwaZulu-Natal Midlands (Figure 1) and Woodbush Arboretum in Limpopo (Figure 2). Ideally the trees would be labelled, but considering that there is a cost attached to this, another standard practice is to have one labelled pole per plot of the arboretum, indicating which species is cultivated in that section. Another option would be to have a labelled pole per tree (Figure 3) or number the trees themselves (Figure 4). What is very important is that there is documentation on the collection that lists not only the taxa cultivated but also the purpose of the arboretum, its establishment date and the origins (country or provenance, seed stock numbers) of the taxa cultivated. Unfortunately, the curation of the data associated with arboreta is frequently the first thing to be neglected. An up to date database is particularly important to visitors in search of particular species or those who wish to expand their knowledge of trees.

Figure 1: Benvie Gardens in the KwaZulu-Natal Midlands, South Africa, contains a remarkable conifer collection, including the genera Cupressus, Chamaecyparis, Picea, Pinus, Sequoia and Metasequoia.

 

Figure 2: Woodbush arboretum was established in Limpopo province in 1907 and contains interesting conifers, such as the China fir (Cunninghamia lanceolata). 

Figure 3: N.M. Tainton arboretum, on the University of KwaZulu-Natal Pietermaritzburg campus, is a remarkable example of an arboretum containing indigenous trees from the KwaZulu-Natal province. The number on the pole next to each tree corresponds to a numbered species list.

 

Figure 4: Numbered trees can be linked to a numbered species list such as these Eucalyptus trees in Draycott arboretum in the KwaZulu-Natal Midlands. This arboretum was lost to fire damage in 2017. 

The life cycle of trees spans many human generations and this makes arboreta useful in investigating research questions that require relatively long time frames, such as climate change and the acclimitisation of species (Gilbraith & Rapley 2005). This is, of course, only possible where the database associated with the plant collection has the necessary detail and has been kept up to date. The long lifespan of trees also make such collections useful as monuments commemorating important historical moments, such as the arboretum in the Afrikaans Literary Museum’s front garden in Bloemfontein (Figure 5), where trees were planted by local or visiting dignitaries. Twenty South African arboreta are currently listed as national monuments (Esterhuyse et al. 2001).

 

Figure 5: Cypress trees forming part of the arboretum in front of the old Government Building, including the Third Raadsaal, today the Afrikaans Literary Museum. These trees are a national monument.

Walking through the arboretum with a hardcopy of the species list and map of the site, enables one to navigate through the collection and make notes as well. However, with modern technology becoming more widespread, there are other ways of giving visitors access to a wealth of information on a species that would improve the educational experience of an arboretum visit (Zimmermann et al. 2013). The name tag could also have a Quick Response code attached to the tree (Figure 6), which can be scanned with a smart phone or tablet. This could direct the visitor to information on the internet about the species, or even a podcast on the uses and conservation status of the species. In an arboretum where all species are tagged it is conceivable that, all too frequently, the visitor will scan a tree tag that indicates the conservation status of this species as ‘NA’ or ‘DD’, i.e., Not Assessed or Data Deficient, which is a reminder that there is a vast amount of research still to be done in conserving and managing the plant kingdom.

Figure 6: Quick Response code attached to the Baobab tree in the Durban Botanic Gardens.

While the goal of a botanic garden is similar—cultivating plants for research, education and display—a botanic garden would often include herbaceous, succulent, graminoid and aquatic species as well as trees. There is no stipulation as to the size or shape of the collection and in an arboretum this will be determined by the amount of land available. The 18^th century botanist J.C. Loudon considered the ideal size for an arboretum to be big enough that each species can eventually display its natural form (Hartley 2007). The first European arboreta were started for aesthetic purposes but also to aid in investigating complicated taxonomic questions that arose from the increasing tempo of species introductions during the 17^th and 18^th centuries (Medbury 1993).

The Company Gardens is South Africa’s oldest botanic garden. It was established in 1652 with the purpose of growing fruit trees but also contained a herb and medicinal garden (Brand 1983). Ornamental plants  as well as indigenous species were introduced by J.A. Auge, who was assistant gardener in the latter half of the 18^th century (Brand 1983) and by 1849 it was formally designated a botanic garden (McCracken & McCracken 1990). The Arderne Gardens in Cape Town, established in 1845, can be considered the first formal arboretum as it was started as an introduction centre for tree species (Lith 2018).

The remarkable success of the first Eucalyptus plantation at Worcester in 1876 and the significant annual costs of importing timber (Van der Zel & Brink 1980) prompted South African foresters to build on this success and experiment further with imported timber species. Shortly thereafter the Forestry Department started experimental arboreta across South Africa to test the climatic tolerance of introduced tree species and to select those that would be commercially viable (Lister 1959). This experiment was devised by D.E. Hutchins, who noted that South African indigenous species were unsuited to commercial forestry “…on account of their difficult propagation, slow growth, and delicacy of constitution…” (Hutchins 1905).

A recent survey found records of 172 arboreta in South Africa of which 51 have been lost over time (Cheek et al. 2022). Slightly more than half of the woody species in these arboreta and botanic gardens in South Africa were alien and they therefore have the potential to be sentinel sites for identifying new pests that may be using the introduced trees as refugia. New weeds could also be escaping from the collections, making monitoring these sites for invasive plants a priority. Simultaneously, arboreta can also play a role in ex situ conservation where alien species are endangered or critically endangered in their native range. The Dawn Redwood, Metasequoia glyptostroboides, was only known through paleobotanic records and thought to be extinct, until live trees were discovered in 1943 in the Shui-sa-pa Valley in Hubei province, China in 1943 (Merril 1948; Ma & Shao 2003), and it is currently considered Endangered globally (Farjon 2013). A large, impressive specimen of this species can be seen at Benvie Gardens (Figure 7). 

Figure 7: The Dawn Redwood (Metasequoia glyptostroboides) at Benvie Gardens. 

Arboreta are also valuable as sites for conservation of indigenous species. Woody species indigenous to South Africa were recorded in 84 of the collections. N.M. Tainton Arboretum, at the Pietermaritzburg campus of the University of KwaZulu-Natal, is one of the very few arboreta consisting solely of indigenous species (Figure 3). Trees representing the coastal, bushveld, forest and rocky outcrop zones of KwaZulu-Natal can be studied here. Collectively, South Africa’s arboreta represent an important resource for conservation and research as well as recreation.

 

Acknowledgments

I am grateful to the South African Department of Forestry, Fisheries and the Environment (DFFE) for funding, noting that this publication does not necessarily represent the views or opinions of DFFE or its employees. I am grateful to J. Robinson, A. Young, W. Simes and M. Clement for permission to include Benvie Gardens, Tainton Arboretum, Afrikaans Literary Museum Arboretum and Durban Botanic Gardens, respectively, in this article. 

 

References

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Cheek MD, Procheş Ş, 2022. The value of arboreta in South Africa. South African Journal of Science. 118(7/8), Art. #12730. https:// doi.org/10.17159/sajs.2022/12730

Cheek MD, Wilson JRU, Richardson DM, Procheş Ş, 2022. The status of arboreta in South Africa and the taxa they contain. Southern Forests: a Journal of Forest Science. DOI: 10.2989/20702620.2022.2102453

Esterhuyse N, Von Breitenbach J, Sönghe H, 2001. Remarkable trees of South Africa. Pretoria: Briza.

Farjon A, 2013. Metasequoia glyptostroboides. The IUCN Red List of Threatened Species 2013: e.T32317A2814244. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T32317A2814244.en. Accessed on 27 June 2023.

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Hartley B, 2007. Sites of knowledge and instruction: arboretums and the ‘Arboretum et Fruticetum Britannicum’. Garden History. 35: 28 – 52.

Hutchins DE, 1905. Extra-tropical forestry: being notes on timber and other trees cultivated in South Africa and in the extra tropical forests of other countries. The Agricultural Journal of the Cape of Good Hope. 26(1): 18 – 32.

Lister MH, 1959. A forgotten experiment in tree planting. The Journal of the South African Forestry Association. 33: 59 – 66.

Lith H, 2018. The Arderne Gardens. Cabo. 2018(1): 7 – 18. Available from: https://journals.co.za/content/journal/10520/EJC-1086a4ce61?crawler=true&mimetype=application/pdf

Ma J, Shao G, 2003. Rediscovery of the first collection of the “living fossil”, Metasequoia glyptostroboides. Taxon. 52: 585 – 588.

McCracken DP, McCracken PA, 1990. Natal, the Garden Colony: Victorian Natal and the Royal Botanic Gardens, Kew. Frandsen Publishers: Sandton. 

Medbury S, 1993. Taxonomy and arboretum design. Arnoldia. 53: 13 – 23.

Merril ED, 1948. A living Metasequoia in China. Science. 107: 140.

Van der Zel DW, Brink AJ, 1980. Die geskiedenis van bosbou in Suider-Afrika. II. Plantasiebosbou. Southern African Forestry Journal. 115: 17 – 27.

Zimmermann HT, Land SM, McClain LR, Mohney MR, Choi GW, Salman FH, 2013. Tree investigators: supporting families' scientific talk in an arboretum with mobile computers. International Journal of Science Education. 5: 44 – 67. DOI: 10.1080/21548455.2013.832437

About the author: Michael Cheek is a botanist attached at the South African National Biodiversity Institute with a research interest in invasive plant species and plant collections research. He believes that integrating the information from biological collections, both living (arboreta and botanic gardens) and dead (herbaria and museums), is a fundamental part of conservation biology.