A close-up view of Edelweiss
Close-up View of Edelweiss
by Brian Johnston (Canada)
Many people know of the Edelweiss from the popular
song composed by Rogers and Hammerstein for their stage play
“The Sound of Music”, which was later transformed into an even
more popular movie by the same name. Unfortunately, the
song gives the impression that the plant possesses snowy white
blossoms, something that is clearly not correct. In fact,
the silvery-white, wooly ‘petals’, with tinges of green, are not
petals at all, but modified leaves called bracts. The true
flowers are small, inconspicuous, and located at the centre of
the rosette of bracts.
The plant’s common name
derives from the German edel,
which translates to noble, and weiss, meaning white. Its genus name Leontopodium derives from
the Greek leon meaning
lion, and podion,
which was the diminutive of pous,
meaning foot – hence lion’s paw. The furry rosette of
bracts that frame the flower-head could, I suppose, be thought
to resemble this structure.
Edelweiss, a member of the Asteraceae family, is
native to Europe and the Alps. Its deep roots protect it
from the high winds and drought that are common in the extremes
of climate found at altitudes from 1700 to 2700 metres where it
An immature flower-head can be
seen in the image below. At this early stage there is
almost no hint of the flowers that will eventually bloom at its
Closer views of one of the
hairy bracts reveal the longitudinal groove that runs most of
their length. In the upper right corner of the first
image, several pollen covered reproductive structures, poking
through the wooly hairs, indicate the location of flowers.
These white hairs are believed to protect the flower-head from
the high ultra-violet radiation levels found at the altitudes
where the plant grows.
Photomicrographs showing these
UV absorbing hairs can be seen below. They form a tangled
mat over the bract’s surface.
The underside of a bract has a
smaller number of hairs growing from its surface, and the
central vein is extremely prominent here.
Two views of the potted plant
used in this article can be seen below. The stems grow to
about 20 centimetres in height, and most flower-heads have a
diameter of about 4 centimetres.
It is interesting to note that
many of the leaves of the plant are not protected by wooly
hairs. Perhaps the mass of flower-heads above, shades the
leaves from most of the damaging UV radiation.
Notice in the rosette of
bracts that frame the flower cluster at its centre, that the
density of white hairs increases towards the centre. Also
note that a few Edelweiss flowers have started to bloom in each
Close examination of the image
on the right below will reveal several blooming flowers, each
with a corolla composed of five, pointed, off-white petals, and
a prominent columnar pistil coated with bright yellow pollen
Side views of a flower-head
and its supporting stem reveal additional information. The
leaves beneath the flower-head are directly connected to the
stem without a stalk (clasping). In the image on the left,
the yellow pistils can be seen to project out of the flowers a
distance greater than the diameter of the flower itself.
The sequence of images that
follows reveals that the flowers bloom first in a ring at the
base of the rosette of bracts. Flowers near the
flower-head's centre bloom up to a week later. The hair
density at the centre can be so great that only the pistil is
able to force its way through the matted hairs to become visible
to an observer.
At the magnifications used in
the images that follow, it is possible to distinguish a flower’s
five petals and pistil.
Some flower-heads have
considerably smaller central areas than others. The one
shown on the right appears featureless, but later, additional
flowers will appear in this area.
Side views of a flower-head
reveal the many pollen covered pistils that project out of the
Now let’s take an even closer
look at Edelweiss flowers. As in many other members of the
Asteraceae family, the
anthers of a flower are concealed within a column up through
which the style pushes the stigma. As the stigma comes in
contact with the pollen covered anthers, pollen grains adhere to
the stigma and are carried with it. In the sequence of
images that follows, notice that so many pollen grains coat the
stigma that it is difficult to differentiate it from the column
itself. In several flowers however, its slightly smaller
diameter, and lighter colour help to distinguish it from the
This is particularly true in
the flower closest to the observer in the image below.
Only the very tip of the stigma is visible in the flower at the
centre of the image.
Now for a surprise! So
far you may have concluded that a flower-head contains only one
central disk of flowers. The reason is simple;
usually only one of the five to ten disks is visible when the
head begins to bloom. Almost as if by magic, the others
begin to appear over a period of several days to a week.
In many cases only the yellow
pistils are apparent, poking through the thick mat of white
Eventually flower disks appear
in the most unlikely places, such as the intersection point of
two bracts (upper right corner of the three images that follow).
Usually the central flower
disk is the most mature.
Sometimes however, the central
disk is the ‘baby’ of the bunch.
As I mentioned earlier, flower
disks can occur in the most unlikely of places. The one
shown below appears to grow directly from the side of the stem!
When a flower disk has
completed blooming, the flowers turn a brown colour, and their
structures begin to disintegrate.
Flower disks adjacent to the
older disks are often in full bloom.
The three images that follow
show a mystery that I have been unable to resolve. If you
examine them, you will see a number of thread-like structures
with bifurcated tips emerging from the mat of hairs. They
look very much like ‘typical’ flower stigmas atop their
supporting styles – but they can’t be since members of the Asteraceae family don’t
have pistils that look like this! What could they be?
If a section of an Edelweiss
flower disk is examined under the microscope, the flowers’
corollas are surrounded by many almost transparent, lobed,
thread-like structures. The petals seen in the images are
immature, and green in colour.
Instead of each flower’s base
possessing a whorl of modified leaflets called the calyx, here
the calyx consists of long, multi-forked transparent hairs.
In the image below, a clump of
Edelweiss pollen grains has glued itself to the tip of one of
The photomicrograph on the
left below shows a single flower before the column containing
stamens and pistil has appeared. On the right is a
slightly older flower in which the petals have opened out into
their final position.
A higher magnification reveals
the cellular structure of one of the petals.
In the two images below, the
column containing the flower’s anthers has projected up beyond
the corolla. As yet however, the pistil has not extended
out of the column.
The following images show the
lobed top of the column, and the pollen covered pistil that has
finally protruded far enough to be visible.
As is the case with most
stigmas, this one has projections at its tip that help to
acquire and retain pollen grains.
Edelweiss is termed a
‘short-lived’ perennial since if its flower-heads are picked
from the plant over a number of growing seasons, it becomes
unable to propagate by seeding. For this reason the plant
is protected in many countries, most notably Austria.
The low magnification, (to
1:1), macro-photographs were taken using a 13 megapixel Canon 5D
full frame DSLR, using a Canon EF 180 mm 1:3.5 L Macro lens.
An 10 megapixel Canon 40D
DSLR, equipped with a specialized high magnification (1x to 5x)
Canon macro lens, the MP-E 65 mm 1:2.8, was used to take the
remainder of the images.
The photomicrographs were
taken using a Leitz SM-Pol microscope (using a dark ground
condenser), and the Coolpix 4500.
A Flower Garden of
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all of my flower articles can be found here.
The Colourful World
of Chemical Crystals
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Published in the
July 2012 edition of Micscape.
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