Lowveld National Botanical Garden

The Lowveld National Botanical Garden, one of the National Botanical Institute’s networks of eight South African botanical gardens, is situated in Nelspruit, the capital of Mpumalanga Province, South Africa. The garden is within one and a half hour’s drive from Maputo, two hours drive from Mbabane, and about three hours drive from Gauteng.

The garden strives to represent the flora of southern Africa’s subtropical areas to the public, with an emphasis on woody taxa. Various inputs in the past 30 years have resulted in the garden, arguably, now containing the world’s largest collection of African tree and cycad taxa.

The garden has three major customers that it services: that of fellow SANBI staff, the public, and researchers from other institutions. A firm belief in delivering quality service to its customer base has made this one of the most esteemed botanical gardens in South Africa and also increasingly so worldwide.

History
The garden originated in 1969 with grants of land from the Nelspruit Town Council as well as from the large farming enterprise, H.L. Hall & Sons, a gift that totalled 159 hectares.

Relief and Climate
The garden straddles the Crocodile River, which has carved a 1-km long, 50-metre deep gorge through a dolerite intrusion in the prevailing Nelspruit Granite. This has resulted in spectacular cascades where the river drops into the gorge and where the smaller Nels River joins the Crocodile River. Both areas offer the visitor spectacular views during floods and the rainy seasons.

The climate is sub-tropical with average daily temperatures of 26–35°C in summer and 18–24°C in winter. The occasional cold snap can however lower temperatures to below 10°C or even as low as -1°C in low-lying areas near the rivers. Four distinct seasons are experienced, with autumn (April–May) and spring (September–October) the mildest and most pleasant. Rain falls mainly in spring and late summer, with a long-term average of 750 mm.

Natural Areas
The natural area of the garden consists of about 134 ha and is of cardinal importance in the ecology of the Crocodile River system. A myriad of vegetation types can be found, from dense riverine forest, semi-arid bush land, and deep sand veld to stunted, alpine-like vegetation on near bare granite domes. Some 590 plant taxa have been recorded as occurring within the natural areas. These include stately Breonardia salicina in riverine situations to the Resurrection Bush (Myrothamnus flabellifolius) on bare granite outcrops. Most of the vegetation is however dominated by closed to open woodland with Combretum collinum subsp. suluense being the dominant tree.

Garden Layout
The developed garden consists of about 25 ha and can be divided into taxonomic, thematic, and ex situ conservation areas. Taxonomic areas are based on collections at the family level and form the framework of the garden’s layout. Owing to climatic constraints, certain taxonomic collections are also situated in certain thematic areas, for example, ferns in the South African forest area.

As far as possible, thematic areas are chosen for exceptionally high diversity or exceptionally low diversity. Thus, one can move from a rain forest with exceptionally high diversity to mopane veld with very low diversity. Thematic areas are also chosen to represent certain Centres of Endemism in South Africa and range from Licuati and Pondoland Sandstone Forests to Sekhukhuneland Arid Bushveld.

Taxonomic Collections
Taxonomic collections are chosen for their largely woody component, the emphasis being on low maintenance of the areas. These areas also play a major role in many research projects by outside institutions, conducting research on phytochemicals and plant pathogens. The large cycad collection is also used as a training area for nature conservation and other law enforcement agencies combating illegal activities in the multi-billion dollar plant industry.

Some 54 taxonomic groupings containing around 700 accessioned species are discretely situated in the garden, often one in the other or close to related families. Most notable collections include the Arecaceae, Bignoniaceae, Combretaceae, Cycadaceae, Ebenaceae, Euphorbiaceae, Fabaceae, Malvaceae, Moraceae, Myrtaceae, Sapindaceae, Sapotaceae, Sterculiaceae, and Zamiaceae.

Landscaping these areas represents a challenge and a Raunkerian system is followed giving an excellent layered outlay. Thus, shrubs and herbs of the same family are preferably used to augment these collections or else a different family (mainly Acanthaceae), consisting of mainly shrubs and herbs, are used to augment beds.

Thematic Areas
Thematic areas are areas in which the environment is actively manipulated to attain a certain theme. For example, the African Rain Forest area receives an additional 1,500 mm of “rain” in the form of large overhead irrigation towers, giving the visitor the climatic effect of being in a high rainfall area.

Thematic areas are mainly chosen for their aesthetic effect on the public and for the fact that it contains one or more taxonomic areas or parts thereof. The arid bushveld area would contain a representative collection of Commiphora species to entrance the visitor with shapes and textures.

Ex Situ Conservation Areas
About 5 ha of the developed garden has been closed to the public for the establishment of population-based South African cycad gene banks. Here, 50–100 individuals of a taxon have been planted as an ex situ conservation measure.

Gene banks are based on seed collected from a known wild source and then cultivated at the garden. Already many of the gene banks are coming into seed production. Seed produced from these gene banks are cultivated by the commercial nursery and sold to the public. It is hoped that providing affordable cycad seedlings to the public could alleviate some of the pressures on wild cycad populations.

Herbarium and Library
The garden also houses its own, well-curated herbarium (acronym GLOW), which contains specimens of all the plant taxa occurring in the natural areas. The herbarium also houses a further 7,000 specimens, mainly from the garden’s immediate vicinity. Most notable collections include those of Ernst van Jaarsveld, Elise Buitendag, and Johan Kluge. The herbarium is actively used for plant identifications by several institutions and the garden staff.

The garden’s library on plant related matters is well known to the public and actively used by garden staff as a reference collection. Subjects range from general horticulture, school- and university textbooks, to regional floras. Several periodicals and journals are also available to garden staff.

Commercial Nursery
The large plant collection of the garden also produces a large amount of seed and cuttings. These are propagated in the commercial nursery and offered for sale to the public and other nurseries. This often results in many rare and interesting plants being available to the public.

The nursery is also actively involved with greening projects in local communities, providing plants at nominal charge to NGOs and during environmental theme days.

The Future
The garden is relatively young, many of the thematic areas still need many years to attain any significant status, and most of the taxonomic areas need to be consolidated. Most plantings have only occurred in the past 15 years and it is thus difficult to visualise the garden beyond an individual’s life span or tenureship. What is clear, however, is that the Lowveld National Botanical Garden, courtesy of its dedicated staff, is one of Africa’s best botanical destinations, now and in the future.

—by Johan Hurter

SABONET News 6.3: 206