Dwarf trees in the fog
Of all the strange and
wonderful trees around the world, perhapse the welwitschia
is the species that looks like an extra-terrestial form of life. Half-buried
in the sands of the lunar landscape of thr Namib Desert.
Tree Tombo NAMIBIA: Welwitschia mirabilis in the desert. It is
surely one of the strangest plants in the world.
Welwitschia has been called the "desert octopus"
because of its huge heap of long leaves.
The Welwitschia mirabilis is
unique to Namibia. It is in fact a coniferous dwarf tree that is related to
the pine tree. It appears as though the Welwitschia has many intertwined
leaves, but in reality there are only two leaves which continue to grow
throughout its lifespan. As time passes, these two leaves are torn into
With the family, genus and
species all rolled into one, Welwitschia mirabilis truly is one of a
kind. A rarity among rarities, it is a dwarf tree found only in the Namib
Desert and on its fringes, northwards from the Kuiseb River. It grows mainly
on gravel plains in the fog belt.
While welwitschias are
classified with cycads and pines as cone-bearing plants, they
are at the same time thought to represent a link to flowering plants. They
live to a great age, as yet not known for certain, but possibly some 2 000
years. The largest trees are only 2m tall with a trunk diameter of 1,5m. Half
of the trunk, or more, remains below ground.
A large colony occupies the
Welwitschia Plain at the confluence of the Swakop and Khan rivercourses in the
northern part of the Namib-Naukluft Park. One of the trees known as the Giant
Welwitschia is estimated to be 1500 years old.
A single pair of
leaves is the sum total of the foliage that welwitschias produce in
their lifetime. The leaves are actually the biggest part of the tree
visible above ground. They grow from opposite sides of the trunk,
straight out of a flattish, woody and dead-looking crown. Long and broad
out of all proportion to the size of the trunk, they rather resemble
floppy conveyor belts at first. In time they come to look like a lot of
long narrow leaves lying in a tangle on the ground because the desert
winds tear them to shreds.
Very tough and leathery,
the leaves never really stop growing out of the crown for any length of
time, not even in the driest years. Wear and tear at the ends keeps them
more or less in check as they grow very slowly. They reach a length of
about 3m. If they are browsed down to the trunk, or broken off, they
immediately start to grow again.
Welwitschias absorb fog water
through minute pores on their large leaves – 250 per square millimetre – as
well as through lateral roots just below the soil. With taproots that are 3m
long, they also depend on groundwater.
Male cones and female cones are
borne on different trees. They first develop at about the age of 20, the
female ones larger, the male ones more numerous. Like the leaves, they grow
from the crown of the stem, but on stalks.
While pollen and seeds are
produced in abundance, the odds against propagation are truly formidable. It
is estimated that only one seed in a thousand reaches maturity. Thereafter at
least 25mm of rain must fall, all at once or within two or three days, for
germination to take place. Which is not exactly an everyday episode in the
The first Welwitschia plant was discovered by Austrian botanist
Friedrich Welwitsch (1806-1872)*
in 1860 in the Namib desert in the
southern part of Angola. The plant was named after Friedrich in recognition of
his successful botanical research and because he found and collected it first.
This Welwitschia is a plant of remarkably bizarre habits and survives in
very harsh localities where the annual rainfall is often less that 25 mm
and where the coastal fog is equivalent to about further 50 mm. The
Welwitschia's oldest living specimens are estimated at 1500 to 2000
years is capable of surviving severe conditions of stress. Most of the
observations are done on the Welwitschia Fläche, a desert plain, about
50 km east of Swakopmund and east of the
the Khan and Swakop rivers
is considered to be a gymnosperm, although the relationship with other species
in this class is not clear. The position of the Welwitschia in the hierarchy
of the plant remains tenuous.
The Welwitschia is endemic to the Namib desert, i.e. found only in the area.
The Namib desert is one of the world oldest deserts with extreme arid
conditions stretches in the western part of Namibia along the coast up to the
south-western part of Angola.
is restricted to a narrow path of this desert. The plant resembles a woody
carrot. The stem is exceedingly fibrous and has a prominent, thick, corrugated
periderm. Unequal growth causes the stems of these plants to become weirdly
distorted and there are only two strap-shaped leaves, growing from a terminal
groove in the photosynthetic tissue of the stem. One of the most magnificent
specimen is found in the Welwitschia Fläche. One of the large plants measure
1.5 m from the soil surface to the highest part of the stem. The Pforte
Welwitschia is 1.2 m tall and the circumference at the base of its leafs is
8.7 m. The roots of Welwitschia can grow up to 30 meters deep, sponge and
lateral roots are also a part of the root system. Leaf characteristics. The
leafs are the longest-lived in the plant kingdom, they are evergreen, a single
pair and generally broad and flat. The broadest unbroken leaf is found in the
Fläche measures 179 sm. This particular leaf was 6 meters long of which 3.15
meters were living tissue. The surface that this leaf covers helps the plant
to survive at a temperature on the soil as high as 65 'C. It keeps the soil
under the plant cool and moist. The leafs grow annually an average 13.8 sm.
Therefore the plant can produce up to 150 m of leaf tissue over a growth
period of 1000 years. The leaves are on average 1.4 mm thick. The leaves that
lay on the sand surface also prevent wind erosion. Even under gale force
conditions the broad leaves remain rigid and immobile. Absorbtion of water
through the stomata must be regarded as very interesting, this characteristics
of the leaves has ensured the species survival. The stomata remains open until
the fog has lifted and although much of the water that has condensed on the
leaves runs off the direct intake of a proportion of this water takes place.
Unlike other plants the stomata is open under foggy conditions
and closes when it is hotter. This ensures that no water is evaporated
during the heat of the day.
Reproductive anomalies. The
below) has large cones while the
male plant (see
below) has flowers. The male
reproductive structure has six stamens each with a anther and a pistil.
A female plant of average size may bear from 60 to 100 or even more
Welwitschia female plant can produce a lot of seeds: up to 10
000 or even more. Unlike other known plants fertilisation occur in the
pollen tube rather than in the embryo sac. It is known that wind plays a
major role in the fertilisation, but much has to be learned about a
little insect (Probergrothiussexpunctalis) which also helps with the
Seed and seedling. The seed units consists of a
seed and a paper husk of winged segments. It is suggested that very strong
wind would be required to successfully distribute the seeds. Most of the seeds
that are shed have a very little chance of germinating. Assuming that 50% of
the seeds are fertile and 80% of that seeds are infected with a fungus (Aspergillus
niger). However, it is doubted that one-hundredth of 1% of all seeds produced
germinate and develop into a mature plant. Seeds that are moisturized
excessively do not germinate but develop an extremely unpleasant odour.
Water absorption. Most plants absorb water from
the soil through their roots. This water is then transported to the stem and
the roots and the water is then lost through the stomata evaporation. The
Welwitschia plant works the other way around. It is able to absorb water from
fog through millions of stomata on the surface of it's large leaves. From
there the water moves to the rest of the plant.
Conclusion. Serious doubts have been expressed as to whether this
wonderful plant, Welwitschia, is not perhaps facing an extinction. Considered
against this plant longevity and remarked adaptation to it's environment,
there should be no reason for concern. It is proper thought that this plant be
awarded the National protection it deserves and in this
respect it is extremely gratifying to know that the Welwitschia Fläche where
the oldest and largest plant occur has now been incorporated into the Namib
Afraid of the Tree Tumbo
call it N’tumbo (stump), the Afrikaans name is tweeblaarkamiedood
(two-leaves-cannot-die), the English common name is tree tumbo, dr. Friedrich
Welwitsch (in Slovene: Velbič), however, wrote about it on September 3rd 1859:
”I am convinced that what I have seen is the most beautiful and majestic the
South Africa can offer.” Dr. Welwitsch kneeled in front of the plant on the
hot sand and looked at it without actually touching it, for had he done so,
the plant would, or at least he thought so, disappear like an apparition. His
name is now immortalised not only in the name of this marvellous prehistoric
plant species, its picture is also carved onto his tombstone. Let’s have a
look at why the plant stirred up the explorer’s imagination and how the plant
can be successfully grown in Slovenia.
Perhabs the oldest Welwitschia mirabilis
in the National park of Namib-Naukluft in Namibia
photo: Vanja Kos . Carbon-dating of the largest Namibian trees
indicates that they are more than 2000 years old.
- Yellowish-green leaves, to 6 feet long.
- Leaves die to brown and tear to shredded
ribbons in the desert winds.
Shape and Trunk:
- Its sprawling ground-level mass of long
dry leaves look as much like a dehydrated monster octopus as a tree.
- "Trunk" is an inverted cone, up to 4 feet
in diameter, which descends 10 feet below the desert, but rises only 3 feet
- This trunk stores water for the tree.
(Rain is absent from its Namib Desert for 3-out-of-4 years. A typical rainy
year has about 1" of rain.)
- Trunk is hard (like hard wood); covered in
a cork-like corrugated bark.
- Each tree is either male or female, and
both have cones.
- A male tree has erect scarlet cones that
rise 1 foot above the trunk.
- Pollen-producing flowers sprout from the
flowers of the male cones.
- Insects carry the pollen to the female
- After the plumper, erect female cones are
pollinated, they produce small, winged, wind-borne seeds.
- Seeds can lie dormant for years.
Grows wild and half-buried in northern
gravel plains of Namib Desert.
Regarded as a "living fossil" connected to
the ancient flora of the Gondwanaland super-continent that existed millions of
Has its own genus as it is so unlike other
Carbon-14 dating has found some
Welwitschia mirabilis to be over 2,000 years old.
Special pores on its leaves help it uses the
dense sea fog and heavy dew that occur year-round.
Its tangled torn leaves also help to
condense air-borne moisture and guide it into the soil around its roots.
Bitterness of leaves and bark deter
Emits a colorless resin that helps protect
it from disease and insects.
Plants may fuse together, either all male,
all female, or a mixture. Groups of five have been found.
Young male flowering plant produces a red pollen which
is Female plant - seed cones.Those are
transferred to the female flower. photo: Kenneth J. Sytsma
Welwitschia beetles which feed off the sap
Female floweing plant is pollinated by a small insect (
Probergrothiussexpunctalis ) and
photo: Dennis W. Woodland.