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CENTURY PLANTS IN
SOUTHERN AFRICA
S cien tists requ ire m ore in form ation on two n atu ralized A g a v e species.
by G ideon Sm ith, Plant S ystem atics R esearch Subdirectorate, N ation al B otan ical Institute,
Pretoria a n d N eil R Crouch, N atal H erbarium , N ation al B otan ical Institute, Durban
n com parison to any area of a
sim ilar size, southern Africa
has the richest flora on earth.
More than 20 000 taxa of vascular
plants (ferns, gymnosperms and
flowering plants) have been
recorded from the subcontinent,
defined here as the area south of,
but excluding, Angola, Zambia,
Zimbabwe and M ozambique.
Not only does southern Africa
generally have a remarkably rich
flora, but with about 40% of the
succulents of the world occur­
ring naturally in the region, it is
also an im portant area for those
interested in this group of plants.
Apart from the rich and diverse
indigenous succulent flora, a
number of introduced succulents
have also found the area suitable
for coloniza­
tion. In this
regard the
exotic cacti
I
Opuntia
ficu s-in d ica
(prickly pear),
O. au ran tiaca
(jointed cactus)
and P ereskia
a cu lea ta
im m ediately
come to mind.
However, not
all succulent
exotics are
aggressive
invaders.
The A gavaceae
The Agavaceae
is a medium38
of course not true that agaves
only flower after 100 or more
years. Another difference
between agaves and aloes is that
some agaves are bat pollinated
w hilst most aloes are bird or bee
pollinated.
Southern Africa does not have
any indigenous representatives
of the family Agavaceae. The
century plant, Agave, occurs
naturally in the arid and semiarid regions of the New World,
particularly the southern parts
of the United States of America,
M exico, some of the central
Am erican states and West Indies
and northern South America.
In the Old World, including
southern Africa, the ‘evolution­
ary’ equivalent of the century
plants would
be the aloe
family
A loaceae (A loe
and its small
relatives, such
as H aw orthia
and G asteria ).
Indeed,
A gave is also
known as the
American aloe.
Although
southern Africa
does not have
any indigenous
species of
Agave, two
century plant
species have
becom e widely
naturalized in
P hoto: Sm ith & C ro u ch .
sized m onocotyledonous family
of about 400 species of m ainly
rosulate leaf succulents. Som e
representatives of Agave, the
principal genus with about 40
species, closely resem ble species
of the African genus A loe in
vegetative morphology. Despite
the superficial similarities, species
of A gave differ from A loe in
many respects, the obvious being
that the m ajority of species are
m onocarpic (plants die after
having flowered). Fortunately for
landscape architects and horti­
culturists, most species of Agave
take several years or even decades
to bloom. The com m on name,
century plants, w hich is widely
applied to species of Agave, was
derived from this character. It is
A g a v e a m e r ic a n a growing near Montagu on the Ouberg Pass.
V eld & Flora June 1996
Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2012.)
the region, particularly in the
several years at w hich tim e it
Karoo and parts of the highveld
produces a pole up to 8 m tall
grasslands and Lesotho. These
with numerous horizontal
branches bearing yellow ish green
are A g av e a m e r ic a n a and
A. sisa la n a . As with several pine
flowers, each with a strong sm ell
and bluegum clones, hakea,
of freshly made fruit salad. This
prickly pear and many other
is a truly m agnificent sight and
species, the two century plants
one that w ill not easily be
have found the southern African
forgotten. The im pact that this
sensational plant had in Europe
environm ent suitable for
successful establishm ent and
following its introduction to
reproduction.
The two agaves
can hardly be
regarded as
invasive,
although the
extent to which
they have
transformed
the areas in
w hich they
have becom e
established has
given rise to
their inclusion
on lists of
southern
African problem
plants.
To determine
the distribution Agave sisalana in suburban Pretoria. Ph o to : Sm ith & C ro u ch .
of A. am erican a
horticulture, must have been
and A. s is a la n a in southern
A frica and therefore the extent
im m ense. Numerous artists
to w hich they have becom e
ranging from im pressionists to
naturalized, the primary source
realists painted A. a m e r ic a n a at
of inform ation is herbarium
the tim e and, apart from the
records with accurate
occasional accurate botanical
distribution data. As in the case
plate, resulted in the production
of m ost succulent plants there is
of a m ultitude of grandiose
a dearth of herbarium specim ens
interpretations of its m agnificent
of these two century plants. This
morphology.
is not surprising if one considers
In contrast, A gave s is a la n a is
the size and leaf armature of the
the w ell-know n source of sisal
mature plants! For this reason
hemp. It has dark green, stiff,
we need your help in drawing
upright leaves that are devoid of
up accurate distribution maps
thorns at maturity. Young plants
in southern Africa of the two
could have very small leaf
agaves, based on sight records.*
marginal teeth. This species is a
The data so collected w ill be
sterile pentaploid and does not
plotted on a map of southern
produce viable seed. It
Africa.
propagates itself by means of
But how does one distinguish
small plantlets that form on the
between the two species of
inflorescence, a phenom enon
A g a v e? Fortunately this is very
known
as vivipary. These drop to
easy. A g ave a m e r ic a n a is the
the ground where they rapidly
well-know n blue-grey agave with
take
root to give rise to colonies
sharp, recurved, black leaf
of
several
metres in diameter.
marginal thorns. It flowers after
V eld & Flora June 1996
The uses of A ga v e in
southern Africa
Species of A g av e must rate as
some of the most widely used
plants in the world. In their
native habitats it is used as food
(flowers cooked in tortillas!), in
the preparation of beverages
such as tequila, as a source of
fabric and brush fibres, as fish
stunners and as soap. But are the
two agaves that
are naturalized
in southern
Africa used
locally? We are
aware that
chopped leaves
of A. am erican a
are picked up
by sheep and
that A. s is a la n a
has been used
as a barrier
plant on some
of the borders
of South
Africa. But
what are the
other uses?
There must be
more. We have
noticed that
portions of the leaves of
A. a m e r ic a n a are entering the
traditional m edicine markets on
the Reef in Gauteng. What are
they used for? Are they sim ply
m istaken for the widely used
A lo e fe r o x ? Please send us any
inform ation on their
utilization.* ®
Acknowledgements
The Mazda W ildlife Trust is thanked for
supporting the Ethnobotany Programme of
the National B otanical Institute at the Natal
Herbarium.
*Can you help?
We need your help in drawing up accurate
distribution maps in southern Africa of the
two agaves. All that is required is to send a
short note, stating where the plant was
seen, to Gideon S m ith at NBI, Private Bag
X 101, Pretoria, 0001. For example,
'A. a m e r i c a n a 15 km north of Oudtshoorn
on the road to De R ust’. One prerequisite is
that the plants must not occur in or in very
close proximity to formal urban, rural or
farm house gardens, i.e. they must not be
recent garden escapes.
If you are aware of any uses that these
plants have been put to please drop Neil
Crouch a line at the Natal Herbarium,
Botanic Gardens Road, Durban, 4 001.
39