Content uploaded by Wilbert Hetterscheid
Author content
All content in this area was uploaded by Wilbert Hetterscheid on Nov 08, 2015
Content may be subject to copyright.
The spectacular inorescence of
Amorphophallus titanum
Plantsman
The
➤
Sp e c i e s o f t h e g e n u s
Amorphophallus are among the
most striking and enigmatic of
all plants. Famed for including some
of the largest ower structures of all
the world’s ora, many members of
this beautiful and diverse genus
remain poorly understood and
seldom cultivated, despite their
spectacular blooms.
The genus was named after the
Greek for ‘misshapen (or deformed)
penis’, in reference to the shape of
the prominent, saggy, spire-like
spadix of the rst described species.
The 200 or so known species of
this tropical and subtropical
herbaceous genus of the Araceae are
distributed mainly in lowland areas
across West Africa, southern Asia
(south of the Himalayas, to China
and the Philippines), to the Pacic
islands. No Amorphophallus are
native to the Americas, although
Dracontium, which are similar but
smaller in size and not closely
related, are endemic there.
Most Amorphophallus species can be
found growing in semi-shady areas in
disturbed ground, such as secondary
forests, but also in grassy savannas.
Many species are found in relatively
localized geographic areas, and
several dozen species remain poorly
understood. These have been
observed only on one or a few
occasions in the wild, and have never
been introduced into cultivation.
All species of Amorphophallus
share the same basic life history.
They are perennial plants that in
their rst year of growth produce
a swollen, underground tuber that
may be globose (as in A. konjac) or
elongated (as in A. macrorhizus and
A. longituberosus), or a horizontal
rootstock formed from a cluster of
consecutive tubers (A. coaetaneus),
or a true horizontal rootstock
(A. rhizomatosus). The different
species vary in the number of years
that they require to mature, but in
most cases, growth is seasonal and
they undergo cyclical periods of
activity and dormancy throughout
the year. The age that individual
plants can reach in the wild is not
known, but likely to be many
decades, or in some cases, possibly
even centuries.
The tubers of Amorphophallus vary in
size, but in the larger species (such as
A. titanum), they are the largest in
the plant kingdom (Gandawijaja et al.
1983) and may weigh as much as
117kg, with a diameter of 1m or more.
The tuber, as a storage organ, is
fundamental to the geophyte life
cycle of Amorphophallus, particularly
in the larger species which may
produce no leaves during years when
an inorescence is produced. In
these cases, the colossal oral
structure develops entirely from the
supply of starch and nutrients stored
in the tuber from the previous
season. Plants tend to ower every
one to two years, rarely longer apart
as in A. titanum.
The foliage of Amorphophallus is
often overlooked in favour of its
exuberant owers. Each plant usually
produces a single leaf during a
Photographs by Stewart McPherson or Jeremy Holden, unless otherwise stated
Amorphophallus
in the wild and
in cultivation
St e w a r t
McPh e r S o n
and wi l b e r t
he t t e r S c h e i d
discuss the natural
history, diversity
of species and
cultivation
requirements of
a legendary genus
of aroids
growing season which emerges from
the top of the subterranean tuber.
It consists of a trunk-like petiole,
that is often variably mottled, which
branches and supports an expansive,
horizontally-held leaf which is
divided into numerous leaets.
In the largest Amorphophallus species
the leaf may resemble a sapling tree,
being up to 6m or more in height
and 7m across. The tree sapling
effect is strengthened by the
mottling which consists of raised
patches, suggesting lichen on a
woody trunk. The foliage is usually
short-lived and collapses within nine
months of developing, often less.
Not all Amorphophallus species
produce large inorescences.
Indeed, most produce inorescences
that are shorter than 1m, and some
are a mere 4cm high. As is typical of
the Araceae, Amorphophallus develop
a compound inorescence consisting
of an elongate or ovate spathe (a
sheathing bract) which usually
envelops the spadix (a ower spike
with a eshy axis).
The spathe shape varies between
species but in the more dramatic
species it is bell-shaped with ribbed
sides and a frilled margin. It is
generally brownish-purple to red or
whitish-green. The spadix may be
yellow, cream, whitish, dark red,
purple or black, and often hollow.
It is completely enveloped in the
spathe and bracts when it rst
emerges. The base of the spadix
bears numerous male and female
orets, more-or-less tightly enclosed
in a chamber created by the spathe.
The female orets are at the base
of the spadix and consist of a pistil.
The male orets sit above them and
consist of stamens. In many species a
specialised zone is found between
the male and female orets; this
either provides food for visiting
insects or carries barrier structures
to temporarily enclose pollinating
insects. Above the male orets is the
terminal part, called the appendix,
which actually consists of fused
sterile male owers (staminodes).
These may form a smooth surface,
or parts of the staminodes may be
visible or transformed to other
structures such as warts or hairs.
In many Amorphophallus species
the life of the inorescence is eeting.
Once the spathe opens, pollination
must happen the same day. Some
Amorphophallus species have a
pleasant odour, but many do smell
strongly of carrion or rotting sh,
distributed by way of the tall spadix.
In the giant species, horticulturists
report that the odour is produced in
waves, but is strongest on the rst
two days that the bloom opens.
The life cycle stages of
Amorphophallus titanum
The foliage of
Amorphophallus paeoniifolius
. The leaves of some of the larger species resemble a young
tree, an effect enhanced by the mottled appearance of the leaf stalk
Lesley Hamamoto
Plantsman
The
➤
The interior surface of the spathe
may bear ridges or warts that attract
mostly smaller beetles. Through a
number of ingenious traps, pollinating
insects are retained inside the spathe
to deposit pollen on the female
owers, which stay receptive for a
single day, while the male owers are
still closed. The male owers open
the next day and shower the trapped
insects with pollen, but by this time,
the female owers are no longer
receptive. Finally, the imprisoned,
pollen-laden insects can escape, and
they transport pollen to another
ower, bringing about cross-
pollination. Unfortunately, this
elaborate owering process may not
result in seed set because different
owers must bloom almost
simultaneously, and within relatively
close proximity. If pollination is
successful the inorescence develops
berry-like fruits which may be red,
orange, white, yellow or blue.
Some Victorian naturalists
thought that the inorescences of
the largest Amorphophallus were
pollinated by wild elephants.
However, ongoing observations have
revealed that in most species,
pollination of the owers is actually
performed only by small insects,
usually carrion beetles.
The genus is famous for including
A. titanum with a record inoresc-
ence height of 3.06m, and A. gigas
which can produce an inorescence
4m high, albeit on a tall peduncle;
these are commonly regarded as the
largest unbranched ower structures
on earth. The largest single ower is
borne by Rafesia arnoldii, and the
largest branched inorescence in the
plant kingdom belongs to the talipot
palm, Corypha umbraculifera. The
gigantic inorescence of A. titanum
is borne at ground level on a very
short scape, whereas that of A. gigas
is less massive, but borne on a much
taller scape up to 3m high. Both
species produce a strong, nauseating
scent giving rise to their local name
of bunga bangkai, or corpse owers,
in Sumatra, Indonesia.
Amorphophallus enthusiast Jeremy
Holden (pers. comm.) describes how
he sometimes found owers by
scenting the waves of odour at night:
‘My guides and I would suddenly get
a potent bout of that indescribable
odour while in camp. ‘Bunga bangkai’
would be the spontaneous chorus,
followed by arguments about where
the plant was located, often hund-
reds of metres away. Conversely, we
might stumble on a scentless plant
while out walking. On one occasion a
guide and myself noted the lack
Amorphophallus abyssinicus
showing the typical arrangement found in the
genus of male owers (here shedding pollen) above the female owers
Wilbert Hettersceid
Wilbert Hettersceid
Although bulbils are usually produced underground, some species, such as
Amorphophallus
muelleri
, bear them on the leaves
of scent. We both moved
in and took a deep sniff – this must
have coincided with a release
because the effect was literally
nauseating. Neither of us could
eat for the rest of the day.’
Amorphophallus titanum was
discovered in the forests of Sumatra
by the Italian botanist and explorer
Odoardo Beccari in 1878. Captivated
by the startling size of the plant,
Beccari dug up a tuber and recorded
that it ‘measured nearly 5 feet in
circum ference, and was so heavy
that two men could scarcely carry
it’ (Anon. 1889).
Beccari’s initial report was met
with disbelief by some. It was not
until the rst specimen owered
in cultivation at the Royal Botanic
Gardens, Kew, in 1889 that the
colossal size of the plant was truly
appreciated. This rst owering
attracted thousands of observers
from across Europe, and it was
reported that governesses were
required to protect young women
from so ‘indecent’ a sight
(Hetterscheid & Ittenbach 1996).
Kew’s achievement in owering
the rst A. titanum is all the more
astounding, since the plant had been
brought to maturity from seed over
a period of only 10 years or so.
One of the more widely known
and commonly cultivated members
of the genus is the smaller A. konjac.
It is cultivated across India, China,
Japan and Korea for its large, starchy
tubers. These are used to make an
edible our or jelly that is commonly
incorporated in a wide range of
Asian cuisines. Amorphophallus
abyssinicus, A. albus and A. paeoniifolius
are also cultivated as crop vegetables;
their tubers need to be cooked for a
long time before they are edible.
The cultivation requirements of
many Amorphophallus remain poorly
The distinctive ower of the commonly cultivated crop plant,
Amorphophallus paeoniifolius
Wilbert Hetterscheid
The tuber of
Amorphophallus paeoniifolius
is edible; this one is about 30cm in diameter
Plantsman
The
➤
documented, but some species can
be cultivated with relative ease, and
encouraged to ower with little
effort. Hetterschied & Ittenbach
(1996) provide the most complete
published overview of the specic
cultivation needs of a wide range of
Amorphophallus species, on which the
following paragraphs are based.
The widely distributed A. bulbifer,
A. konjac (usually grown under the
name A. rivieri) and A. paeoniifolius
are the easiest to grow. They are
readily available through tropical
markets and specialist tropical bulb
suppliers. These species require rich,
well-drained soil or compost, occas-
ional fertilizing, shade from direct
sunlight, a minimum temperature of
22°C in the day and 19°C at night,
and a well-dened resting period.
An
Amorphophallus
species encountered on Mount Halcon in the Philippines – the fused staminodes making up the appendix give it a warty appearance
A potentially new species from Vietnam
Amorphophallus beccarii
, a Sumatran species
Depending upon the species, during
dormancy the tuber should either be
dug up and stored in a cool, dry
position, or left in the substrate.
It is likely that most other Amor
phophallus species can be cultivated
successfully in similar conditions,
although a few from more arid
habitats will require a drier regime.
Unfortunately, the giant species,
A. gigas and A. titanum, are more
difcult to cultivate because their
huge tubers are prone to rotting.
They also require enormous growing
spaces, and are less likely to produce
seeds or offshoots. However, if
grown in well-drained conditions
with considerable care given to
dormancy, both may be cultivated
to maturity in 10-–15 years. They will
ower every 2–3 years if suitable
conditions are maintained.
Most of the smaller Amorphophallus
species readily produce offsets every
year. These should be severed and
planted separately when the mother
tuber is replanted for a new season.
The percentage that establish succ-
essfully as separate plants varies
considerably; some may remain
inactive for years without sprouting
before nally dying. Conversely, a
latent offset may start growing
spontaneously after years, so tubers
should not be discarded until dead.
Certain species produce bulbils on
the leaves. In some, a bulbil develops
on the surface of leaet branching
points (A. bulbifer and A. muelleri),
whereas in others the entire
branching point of the leaf develops
into a bulbil and is released when the
leaf rots away (A. angulatus, A. manta,
and A. sparsiorus). Once detached,
the bulbils may be planted separately
and treated as an adult plant.
Cuttings can also be made from the
leaves and parts of the tuber,
although with variable success.
Some Amorphophallus species
produce seed without articial
pollination (A. bulbifer, A. kiusianus
and A. muelleri), although most do
not. If pollination is attempted in
cultivation it must be done on the
rst day of owering to t with the
plant’s owering physiology. Self-
pollination does succeed in a few
taxa, though this usually leads to a
very poor seed-set.
Articial hybrids have been
created in cultivation, for example
A. albispathus
x
A. longituberosus and
A. odoratus
x
A. yunnanensis, although
these are not widespread.
When harvesting, the seeds may
be removed from the berry esh but
must not be allowed to dry, as this
can cause fatal desiccation of the
embryo. Fresh seed of
Amorphophallus usually germinates
quickly, within 1–3 weeks, when
sown on moist, nutrient-poor,
slightly acidic compost. Notable
exceptions include A. henryi and
A. kiusianus, which may take a year
or more to germinate. The rst
seedling leaf is often not very
divided, becoming more so in
successive leaves. Seedlings may
produce many leaves over their rst
season before their rst dormancy
period starts. Dormant young tubers
are best left in the soil until they are
larger and more resistant to drought.
Amorphophallus
Some botanic gardens have amassed
extensive collections of
Amorphophallus for research or
display. Those with the best
collections accessible to the public
are at the Leiden Botanical Garden
in the Netherlands, Hamburg
Botanic Gardens (the largest of its
Move these
two pics to p93
Amorphophallus napiger
, a species from Thailand The tall inorescence of
Amorphophallus gigas
Plantsman
The
kind and the former research
collection of Wilbert Hetterscheid),
Bonn Botanic Garden in Germany,
Roayal Botanic Gardens, Kew, in the
UK, Bogor Botanic Garden in
Indonesia, and the Fairchild
Tropical Botanic Garden in the USA.
Seeing A. titanum ower in the
wild requires patience. Although
they usually ower after four years at
the ‘petiole stage’ there is no advance
warning (unlike with Rafesia where
buds can be located). The ower
may only exist for 24 hours, usually
opening at night, before closing up.
This means most owers that locals
nd are already closed before news
gets out. One of the best places is
Batang Palupuh reserve, 20km from
the town of Bukittinggi, West
Sumatra. It was set up to protect
Rafesia arnoldii, and Amorphophallus
titanum can sometimes be seen there.
If owering specimens are not found
within the reserve, the helpful guides
can usually lead visitors to view
plants in surrounding forests within
a few days. The reserve does not
have a website but it is easily
accessible from Bukittingii without
an appointment.
The International Aroid Society
(www.aroid.org) offers excellent
information for those interested in
Amorphophallus. The society’s
members and listed aroid nurseries
are the best sources to acquire
infrequently cultivated Amorphophallus
species (one good source is www.
wistuba.com).
All who are new to Amorphophallus
cultivation are strongly recommended
to read Hetterscheid & Ittenbach
(1996), the most complete
horticultural overview of the genus.
At the start of the 21st century we
are only beginning to understand the
diversity and taxonomy of this extra-
ordinary genus. Many species are
infrequently observed, and the basic
aspects of their biology and ecology
are still unknown. Also, new species
continue to be discovered as remote
parts of tropical Africa and southern
Asia open for exploration.
However, their extraordinary
ower shapes, colours, scents, and
sometimes gigantic sizes, make them
fascinating plants to cultivate at
home, often in conditions that are
relatively easy to provide.
st e w a r t Mcph e r s o n is a
plant explorer and writer with a
particular interest in unusual plants
wi l b e r t he t t e r s c h e i d is
Director of Von Gimborn Arboretum,
the Netherlands. He is preparing a
revision and phylogeny of
Amorphophallus and he also has a
taxonomic interest in Typhonium
and cultivated plants
The authors would like to thank
Alastair Robinson, Andreas
Fleischmann and Jeremy Holden for
their kind help in editing and
sourcing images for this article.
Anon. (1889) A vegetable titan.
Gard. Chron. 129(5): 750
Gandawijaja, D, Idris, S,
Nasution, R, Nyman, LP &
Arditti, J (1983) Amorphophallus
titanum Becc. A historical review and
some recent observations. Ann. Bot.
51(3): 269–278
Hetterscheid, W & Ittenbach, S
(1996) Everything you always wanted
to know about Amorphophallus, but
were afraid to stick your nose into!!!!!
Aroideana 19: 7–129
Finding the owers of
A. titanum
can be a challenge, but they can often be tracked down by scent
