Close-up View of a 'Hen and Chicks' Hybrid Sempervivum tectorum 'Red'
Close-up View of a
'Hen and Chicks' Hybrid
by Brian Johnston (Canada)
are extremely hardy, mat-forming succulents of the family
known as ‘Hen
and Chicks’ or ‘Houseleeks’. Native to the mountains of
the Middle East, and Central Asia, they grow close to the
fleshy leaves grouped around one another in a very tightly
rosette. The ‘hen’ is the main plant, and the ‘chicks’ are
offspring, which start as tiny buds on the main plant, and soon
their own roots, taking up residence close to the ‘hen’.
Hens and chicks have a very
history of cultivation. It is said that the Frankish King
Charlemagne (742-814 AD) suggested to his subjects that they
plant on their thatched roofs in order to guard against fires
thunderbolts, storms and sorcery. Since succulents do
water in their leaves, they may help in the first two cases, but
sorcery – perhaps not!
The genus name Sempervivum is Latin for
alive’ (evergreen). Tectorum,
the species name is also Latin, and translates to ‘on
Thus – the plants live for extended periods on rooftops.
Anyone growing hens and chicks
knows that there is a small ‘fly in the ointment’ however.
Most Sempervivums are
monocarpic, meaning that
particular hen flowers only once, and then it dies.
by the time that this happens (usually several years), it has
produced many chicks to take its place. I was fortunate to
at my local greenhouse, a striking cultivar that had a single
the process of flowering. This article is the result.
The first image in the article
shows a few of the beautiful pink, star-shaped flowers that
blooming stalk. The series of images below shows the
the flowering process. Notice that the hen, which
a tightly packed rosette of leaves, has extended upward an
distance (about 20 centimetres at this point). Hidden
fleshy leaves is a 1.2 cm diameter stalk, and at the point where
leaf joins the stalk, a group of buds extends out on its own
stem. Only a few of the buds have opened to reveal
Closer views of the flowers
that they are (actinomorphous),
like a star, with about 15 pinkish-white petals. The
most noticeable characteristic of a flower is the ring of
arising from the disk at the base of the petals.
filaments are bright red in colour. Depending on whether
immature or mature, anthers appear pinkish-red, or bright
This phenomenon will be discussed in more detail later in the
It is simply amazing how the
tightly packed leaflets at the top of a hen rosette are suddenly
carried aloft by the rapidly growing stalk of the plant.
top of the stalk, clusters of pale pink, furry buds grow out
gaps between the leaflets.
Closer examination of one of
leaflets reveals its cellular structure, and the closely spaced
needle-like hairs that ring its edge.
Each of the buds is ringed by
green sepals which
sharply pointed tips. These sepals surround the pink
flower petals that
extend beyond them.
As we move closer to the buds,
becomes apparent that the surfaces of both sepals and petals are
remarkably hairy. Most hairs are colourless, which
their visual contrast with the green sepals and pink
Close examination also shows that at a very early stage, the
pinkish in colour, and only later does their green colouration
If you look carefully at the
of the sepals in the two high magnification macrophotographs
follow, you can see the strange, bright red, bulbous structures,
of which has a ring of colourless hairs arranged radially in a
configuration. How strange!
Over a period of several days,
begin to open. The two images below show this process at
To give some perspective, here
two images that show the entire group, consisting of a hen and
off-shoot chicks, that was the subject of this article. At
point, the accumulated weight of the leaflets, buds and flowers
become so great that the hen’s stalk has begun to bend
alarmingly. At no point however, did the stalk give
The first image gives a clue to the inevitable future of the
the bottom-most leaflets have already begun to turn brown.
A view of the ‘back’ of the
stalk reveals its cylindrical, light green structure. Note
the base of a leaflet grows directly from the stalk. Also
the narrower diameter of one of the stalks supporting a cluster
Here is a group of images
some of the ‘chicks’ that surround the blooming ‘hen’.
sharply pointed tip of each leaflet.
Higher magnification once
reveals the closely spaced, tiny hairs that grow from the edge
Once the plant begins to
resulting flowers are remarkably long-lived – up to two
The top of the stem is abundantly covered with blooming flowers
buds, producing a stunning, and unusual display.
Now lets ‘zoom in’ on the top
the stalk in order to see the profusion of colourful,
The flower in the lower left
of the image below has just opened. Notice that the two
anthers are deep reddish-pink in colour. At the centre of
rings is a group of hair-like, purple protuberances that are, in
the flower’s pistils. By contrast, the flower in the upper
corner of the image opened several days earlier. Here the
are bright yellow, with a deep purple furrow bisecting each into
In some areas, all of
flowers’ anthers are releasing bright yellow pollen.
In the flower shown at left
all of the anthers are covered by a thin purple membrane which
the developing pollen grains beneath. In the image on the
half of the protective purple membranes have disintegrated,
yellow pollen releasing anthers. Notice in both images,
tips of the flower’s petals.
Under the microscope, the
of these petal tips are easier to resolve. Many pollen
adhere to the colourless hairs that cover the tip’s edge.
A higher magnification shows
the pollen grains are ellipsoidal in shape.
Although it is difficult to
the surfaces of petals are also covered by hairs.
of these can be seen to have bulbous tips in the lower left half
image. The bulbous tips imply that the hairs may be
Additional images showing
glandular hairs can be seen below.
Still higher magnification
the structure of the base of the hairs.
Each of the plant’s flowers
diameter of about 2.5 cm. What does its supporting stalk
The answer can be summed up in
word – hairy! Extremely fine, and remarkably soft hairs,
in the stalk feeling downy.
Let’s look more closely at the
flower’s stamens. As mentioned earlier, when the flower
opens each anther’s exterior surface is covered by a thin
The membrane appears to be
by a lighter band that can be seen in the image below.
Closer examination using a
microscope however, reveals that some of the membranes are
four quarters by two longitudinal bands. Most however, are
The cells composing the
bands are larger than those that make up the rest of the
membrane. When the membrane begins to disintegrate, the
starts along these lighter bands.
Pollen grains from mature
in the vicinity have ‘stuck’ to the surface of one of the
(left image), and to the anther’s supporting filament (right
The two images that follow
the moment when an anther’s membrane begins to split
along the band. A copious quantity of bright yellow pollen
In the flower shown below,
of the anthers has begun to expose its pollen, and if you look
a small segment of the purple membrane still remains in its
The membrane disintegration
has happened to a greater degree in the flowers shown in the
that follow. Strangely, the dark, deep purple bisecting
each of the mature anthers started out as the lighter coloured
its immature stage!
At the centre of the circle
by the flower’s stamens, there is a group of what look like deep
hairs. These are the female pistils of the flower.
Under the microscope, a pistil
be seen to have a white tip – the stigma. Beneath the
its bright red supporting style. The image on the right
group of pollen grains that have adhered to the pistil’s
Even the lighter coloured base
the style is pollen covered (left image). Higher up the
(right image), its surface has been damaged, allowing us to see
long, thin cells of which it is composed.
Here all but three of a
anthers have fully matured.
The final stage of the
process shows all of the anthers mature.
One of the flower’s petals can
seen in the two images that follow. Notice on each side at
base, the brilliant red globular tips of two of the flower’s
Even at the high
magnification of the image on the right below, it is not really
possible to distinguish individual pollen grains.
Under the microscope, using
power, it is still difficult to resolve single grains.
At much higher magnification
however, their ellipsoidal shape becomes apparent.
The seeds produced by the
of a particular Sempervivum plant
be used to grow another, however they usually do not breed
to their parentage. New variations are often produced in
reproduction occurs when the hen ‘offsets’. Here,
of the hen produces what look like thin, root-like stems called
stolons with tiny
chicks at their
ends. Each offset develops roots of its own and becomes
independent of the parent when the stolon withers and
Sempervivums produce offsets on the ends of long stolons, which
produces a less tightly packed family group. Vegetative
reproduction produces offspring with the same characteristics as
Hens and chicks are extremely
popular as rock garden plants. This popularity has
resulted in an
amazing number of ‘common’ names being given to the them.
of them are: Houseleek, Jupiter’s Eye, Jupiter’s Beard, Thor’s
Bullock’s Eye, Sengreen, Ayron, Ayegreen, Aaron’s Rod, Hens and
Liveforever, and Thunder Plant!!
The low magnification, (to
macro-photographs were taken using a 13 megapixel Canon 5D full
DSLR, using a Canon EF 180 mm 1:3.5 L Macro lens.
A 10 megapixel Canon 40D DSLR,
equipped with a specialized high magnification (1x to 5x) Canon
lens, the MP-E 65 mm 1:2.8, was used to take the remainder of
The photomicrographs were
using a Leitz SM-Pol microscope (using a dark ground condenser),
the Coolpix 4500.
A Flower Garden of
A complete graphical index of
of my flower articles can be found here.
The Colourful World
A complete graphical index of
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the
February 2012 edition of Micscape.
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