The flora of southern Africa (Namibia, Botswana, Swaziland, Lesotho, South Africa) is very rich and diverse with over 24,000 species distributed over a number of biogeographical regions. One of the strengths of the South African National Botanical Institute (NBI, now SANBI) has been its national network of eight gardens spread across several of these regions. This enables it to grow many species under conditions close to that of their natural areas.
The living plant collections at Kirstenbosch play a pivotal role in helping the NBI achieve its mission to “promote the sustainable use, conservation, appreciation, and enjoyment of the exceptionally rich plant life of South Africa, for the benefit of all its people”.
Kirstenbosch is the largest and second oldest of our botanical gardens; only the Natal National Botanical Garden is older. It receives a large number of tourists and professional visitors. The garden is located in Cape Town, which experiences a mild Mediterranean climate with most rain falling during the winter months, and has traditionally grown a representative range of our flora. The summers are warm and dry, making it a very good climate for growing a range of plant types. In addition, a conservatory has been built to house xerophytic plants that cannot be grown outdoors. As Kirstenbosch is located in the centre of the Cape Floral Kingdom, the main emphasis of the garden is on plants from this region.
The Kirstenbosch collections can be divided into two categories. The first category comprises those collections grouped into families or parts of families, including Protea (Proteaceae), Erica (Ericaceae), Restio (Restionaceae), Pelargonium (Geraniaceae), buchus (Rutaceae), Streptocarpus (Gesneriaceae), ferns (Pteridophytes), Disa (Orchidaceae), cycads (Zamiaceae), and clivias.
The second category comprises collections of similar plant form or habitat, such as trees and shrubs, alpines, succulents, bulbs, and annuals and herbaceous perennials.
Read about the maintenance of these collections
Protea
Collection
The Proteaceae, Restionaceae, Ericaceae, and Rutaceae
families form the Fynbos collection at Kirstenbosch. Thirteen of the 14 genera
and 220 of the 387 species are represented in the collection in the garden
and nursery. In addition, 74 of the 161 rare and endangered species are grown.
Leucospermum,
Leucadendron, and Protea are
the main genera represented. The collection in the garden has been planted
with plants from other fynbos families and is aimed at providing horticultural,
as well as botanical, interest. Schools and tertiary educational organisations
use the collection intensively. It is also very popular with tourists.
Restio
Collection
The family Restionaceae forms an integral part
of Fynbos vegetation. The Restios are divided into 19 genera, of which
13 are represented in the collection. Fifty-five of the 314 species are grown
at Kirstenbosch, including eight of the 65 rare and endangered species. The
collection is used for education and research. Horticultural research into
germination methods for this group has seen great strides over the last decade;
previously, very few species could be germinated. The germination of the nut-seeded
species still presents a challenge. Plants are displayed in the garden to
test their potential and promote them to nurserymen and gardeners. The species
are tested for their longevity and horticultural potential. Selected species
are mass-produced and sold to the wholesale trade as seedlings or bigger plants.
Erica
Collection
The Erica
collection is a representative display of the largest genus in South Africa—Erica comprises about 660 species, of which
more than 430 occur in the southwestern Cape. The collection consists of about
252 species of which many are displayed in the garden. A special pot collection,
which includes the rare and endangered species is housed in the nursery. Fifty-three
of the rare and endangered plants are grown. The collection serves as a source
of material for reintroduction programmes. Two species extinct in the wild,
Erica verticillata and Erica turgida, have been successfully reintroduced
to a local nature reserve on the Cape lowlands. The collection serves as an
educational, research, and horticultural resource.
Rutaceae
Collection
There are 14 genera in the Rutaceae; most are
fynbos species occurring in the Cape Floral Kingdom. The Kirstenbosch collection
consists of 11 genera and 122 species. This group of aromatic shrubs includes
some of the most promising horticultural plants in the country. A number have
become very popular garden subjects and are arousing interest overseas. As
with other fynbos plants there are some that still present horticultural problems.
This group is represented widely in the garden and in a dedicated section
of its own. A pot collection of selected forms is grown in the nursery.
Pelargonium
Collection
The genus Pelargonium
is part of the Geraniaceae family and consists of about 220 species. Most
are found in southern Africa with about 80% confined to the winter rainfall
area of the western Cape. Pelargonium
is a very diverse genus and is divided into 14 taxonomic sections. The collection
houses 119 species representing all 14 sections and thus displays the range
of diversity of the genus. The collection is a good source of plant material
for the University of Stellenbosch for DNA studies; it is also being investigated
for potential anti-bacterial properties. Plants are displayed in a section
in the garden and in a comprehensive pot collection in the nursery.
Streptocarpus
Collection
This is a small collection of ornamental plants
with a lot of potential as breeding stock. Streptocarpus is used in various shade sections of
the garden and in the conservatory for display. The main collection is housed
in the nursery.
Disa
Collection
Orchids are a diverse and specialised group.
Orchid collections require intensive maintenance and the Kirstenbosch collection
is therefore limited to some of the species in the genus Disa and especially the different forms
of Disa uniflora that occur in the
southwestern Cape. These forms are selected for use in breeding programmes.
This orchid is exceptionally beautiful and has been recognised locally and
overseas to have good cut-flower and pot-plant potential. An effort has been
made to rebuild the collection after a period of neglect. The collection is
housed in the nursery and flowering specimens are displayed in the Botanical
Society Conservatory.
Fern
Collection
There are about 331 known native species of pteridophytes
in the southern African sub-region, of which 246 occur in southern Africa
(including Botswana). The fern collection houses 72 species of which 28 are
endemic to the Cape Peninsula. The collection is housed in a glasshouse and
is used intensively for educational purposes. Plants are displayed in one
of the corner units of the conservatory.
Cycad
Collection
The cycad collection at Kirstenbosch is the largest
cultivated collection in existence. There is no active collecting to increase
the collection—the main objectives of the collection are conservation and
providing information on the propagation and cultivation of cycads. Rare and
endangered species are grown for distribution to botanical gardens worldwide.
Pollen and seed are also distributed. The collection is displayed in the cycad
amphitheatre and in the nursery.
Clivia
Collection
At present, the Clivia collection is not as representative as we would like and John
Winter is actively collecting to improve it. The objective is to systematically
collect as many forms of Clivia miniata,
C. nobilis, C. gardenii, and C. caulescens throughout their known distribution as possible, and
to bulk up the material collected for display in the garden.
Bulb
Collection
The collection comprises approximately 700 species.
Bulbous plants from all parts of South Africa are cultivated, but most are
winter rainfall species, due to the exceptionally high number of species that
occur in this region. The bulk of the collection is housed in the nursery,
under cover, as many of the species cannot survive the heavy winter rainfall
and heavy soils in the garden. In addition, many bulbs fall prey to moles,
porcupines, and guinea fowl if planted in the garden. Only the toughest bulbs,
such as Watsonia, Agapanthus, Dietes, and Clivia can be
grown successfully. A major function of the collection is for horticultural
and taxonomic research, which has given rise to a number of books. Attractive
genera are displayed in the Kay Berg Bulb House in the Botanical Society Conservatory.
Seed is collected and distributed to members of the Botanical Society and
for sale. Approximately 100 rare and endangered species are maintained in
the collection, and where possible, re-introduced into the wild, or distributed
to other botanical gardens worldwide.
Alpine
Collection
The Alpine collection is one of the youngest Kirstenbosch
collections. The alpine flora of South Africa—although unfamiliar to the South
African gardening public—is attracting much overseas interest. The collection
is drawn from the Lesotho highlands and the Drakensberg. Collections are also
made from the high mountains in the southwestern Cape. The developing collection
is housed in the nursery and plants are displayed in one of the specialist
units in the Botanical Society Conservatory. Many of the plants require special
growing conditions, such as high light intensity and low moisture and humidity.
Horticultural research is being conducted to determine their horticultural
potential and methods of growing and displaying these plants. The Alpine group
has been determined to have about 137 genera and over 300 species.
Succulent
Collection
This is a representative collection of the South
African succulent flora and other xerophytic plants, with an emphasis on plants
with horticultural potential and those that are rare and endangered. It consists
of the collection in the gardens in the Mathews’ Rockery and other rockeries
displaying Aloes and the Lampranthus
group. Collections needing protection from the weather are kept in the nursery
and as display material in the Botanical Society Conservatory. There is also
a concerted effort to make succulent plants available to the public and other
botanical gardens. The strength of the collection lies in groups like Aloaceae
and Mesembryanthemaceae families. About 1,000 of the approximately 4,000 indigenous
succulent species are represented.
Current research is being done into the horticultural potential of succulents as garden and houseplants as they are true “waterwise” plants. A study of the cliff-dwelling succulents is also being done and a section of the Conservatory is being developed to display these. Regular field trips are undertaken to increase the range of the collection with special emphasis on medicinal plants. The Botanical Society Conservatory is five years old and most of the plants, including the baobab, are well established. Education is seen as one of the major attributes of this collection. Garden staff have published a number of books, papers, and magazine articles to popularise succulents.
Trees
and Shrub Collection
This is a representative collection of South African
trees and shrubs. The emphasis is on plants with horticultural potential and
those that are threatened or rare. The collection is represented throughout
the garden with the subtropical coast section displayed in Section Q. The
collection serves as material for display, research, and education. Material
from this collection is propagated for sale to the public and distribution
to other botanical gardens. The strength of the collection is in the representation
of plants from the subtropical coast, a complete Ficus collection, and afro-temperate forest
species.
At least 350 of the approximately 1,000 South African tree species are grown at Kirstenbosch. Current activities include establishing a subtropical forest, making use of natural succession using Virgilia and Trema orientalis. Plants of the local silver willow, Salix mucronata subsp. hirsuta, which became extinct in the Cape Peninsula, have been reintroduced into the streams at Hout Bay and Constantia. Field trips are aimed at collecting species that will be useful introductions.
Herbaceous
Collection
Herbaceous plants include annuals, herbaceous
perennials, such as Diascia, Plectranthus, Sutera, Lobelia, and Nemesia, and a range of free-flowering
plants that are used to great effect in the most visited parts of the garden.
This group consists of some of the most colourful species and is a group recognised
overseas as having huge commercial potential. This is still a relatively young
collection and growing rapidly with an almost unlimited resource of suitable
material in all regions of South Africa. The main function of the group is
display with the emphasis on spring and summer when most of our visitors come
to Kirstenbosch. The Diascia collection has also been the subject of pioneering research
on plant–insect interrelationships (pollination biology).
Maintenance
of the Collections
Collections held at Kirstenbosch and other botanical
gardens are a valuable resource. A lot of time and resources are dedicated
to develop them and research them. It is therefore imperative that this effort
and expense are not wasted. At Kirstenbosch, a maintenance plan is being established
to ensure that the essentials of day-to-day and season-to-season maintenance
of the collection are documented in detail. This information is not only necessary
for the present incumbents, but also for future persons who would be required
to look after our collections. We hope that with the introduction of the maintenance
plan, which will be updated and amended on an annual basis, we can improve
on the quality and sustainability of these valuable national collections.
—by Anthony Hitchcock
SABONET News 5.3: 173
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also see the Kirstenbosch Threatened Plants Programme
