Close-up View of the
Pieris japonica 'Mountain Fire'
by Brian Johnston (Canada)
Pieris, or Andromeda as it is sometimes
called, is a broadleaf evergreen
shrub used in shaded temperate gardens. Most Pieris cultivars are hybrids of two
Asian species, Pieris japonica
and Pieris formosa, because
both possess bright red leaves in the early spring. Unfortunately
these cultivars require rather warm conditions to grow
successfully. In order to obtain better hardiness, Pieris ‘Mountain Fire’ has a third
species added to the hybrid mix, namely Pieris floribunda, which is native
to North America.
The three-species hybrid ‘Mountain Fire’ is so called because of the
new-growth, bright red leaves that develop in late winter, and early
spring. These colourful leaves quickly change to a mahogany
shade, and then to deep shiny green. Since the plant is an
evergreen, it has a dazzling display of bright red new-growth
contrasting with the older, deep green leaves of the previous
year. Since the plant’s flowers are white, and relatively small,
some gardeners consider the contrasting leaf colouration to be the
plant’s most appealing characteristic.
Japanese Pieris has several alternative names. The small, white,
bell-like flowers suggest one of these alternatives, the “Lilly of the
Valley Bush”. Two other alternatives are “Andromeda” and
“Fetterbush”. These latter names are derived from the Greek myth
in which a princess of Ethiopia, Andromeda, was chained to a sea wall,
and threatened by a sea monster. The hero of the story, Perseus,
saves Andromeda from certain death by breaking her chains, and freeing
her. How does all of this relate to the plant? The
pendulous chains of white Pieris flowers evoke the chains holding
Andromeda to the wall! “Fetterbush” also relates to the captive’s
The red spring growth can be seen in the following images. At
first, the topmost leaves are positioned vertically, but as can be seen
in the second image, they soon move to their final horizontal
The new shoots start as bud-like forms at the tip of last year’s
growth. On the right, the tiny red leaflets at the tip of a new
growth shoot are almost ready to separate from one another.
Shortly after, the new-growth tip displays its topmost, newly opened
leaflets, and the unusual green pseudo-leaflets that eventually fall
off, leaving tiny scars.
The tip of one of the bright red leaflets can be seen in the two
photomicrographs that follow. Notice the very strange, scarlet,
egg-shaped structures that are connected to the leaf by white
stalks. They grow at each V-shaped notch along the leaflet’s
edge, and randomly on its veins. (I have been unable to ascertain
the function of these unusual objects.)
In the central area of a leaflet, there are literally hundreds of these
structures. The higher magnification image at right shows the
tiny hairs that are present on the veins, and to a lesser degree on the
At a much later stage, the ring of topmost, new-growth leaflets has
almost progressed to its final mature state. The leaves are even
more brightly coloured than before! In the final stage of the
transformation, the leaves’ colour turns to the bright green that can
be seen in the previous season’s leaves.
Pieris flower buds are unusual in that the pale green sepals (modified
leaves) that cup the bottom of each bud, fit into deep grooves in the
assembly of unopened petals (corolla).
Flower strands grow at the base of each new-growth stalk, and they
overhang the old-growth leaves.
The corolla (petal assembly) of each flower is fused, with the
exception of the tips. Pale beige sepals still cling tightly to
the flower’s base. The white pendulous flowers are attached to
the stem by very short stalks. Although one common name for the
plant is “Lily of the Valley Bush”, the Pieris flowers are much longer
and more tubular in shape than those of the Lily of the Valley.
Pieris flowers grow in chain-like clusters which may hang vertically,
or occasionally, be positioned partially upright. In both cases,
the flowers are held on only one side of the stalk.
If you look carefully, you can see that some of the flower stalks have
tiny, pale green leaflets growing along their (short) length.
The pearly, translucent, fused petals that form the flower’s corolla
have darker longitudinal lines appearing like faint stripes. The
occasional sepal tip (third image), and petal tip (first image), is
coloured bright red or pink.
The pale longitudinal lines mentioned earlier can be seen in the
following higher magnification images. Notice also, that the
sepals have darker coloured specks on their surfaces.
If a flower’s corolla is dissected away, the striking reproductive
structures can be seen more clearly. A ring of anthers (male
pollen producing organs) and their supporting filaments, can be seen
just above the flower’s base. The gaps between the hairy, white
filaments reveal the deep green ovary (seed producing structure).
Projecting vertically from this ovary is the flower’s pistil, composed
of a dark green stigma (female pollen accepting organ), and a paler
green supporting style. Note in both images, the light coloured
pollen on the anthers, and the two strange, brown, tail-like
projections that sprout from each anther.
These anther “tails” can be seen more clearly in the vertical view
(left), and photomicrograph (right) below.
A photomicrographic side-view of an anther, and a close-up of its
surface follow. Notice the hairy white filament in the left image.
A view of the back surface of an anther, with its point of attachment
to the filament, is shown in the left image. The photomicrograph
at right shows a close-up of the surface.
Under the microscope, the filament appears to be entirely covered with
long white hairs.
The stigma’s receptive tip can be seen in the photomicrograph that
follows. Several pollen grains are clinging to its surface.
The tip of another stigma is liberally coated with an extremely sticky
liquid which aids in the retention of pollen grains.
A higher magnification photomicrograph of the style shows its cellular
structure. A Pieris pollen grain can be seen at right.
After blooming, the flower’s corolla disintegrates, and falls
away. The sepals then move closer to the style, effectively
protecting the developing ovary. As can be seen in the image, the
stigma and style begin to dry out, and in some cases, fall away.
The front surfaces of several Pieris ‘Mountain Fire’ leaves can be seen
below. They are glossy and bright green.
In contrast, the back surface of a leaf is less glossy and paler green.
The final two images show the stem and leaves of another Pieris
cultivar taken the previous summer. Notice the distinctive red
growths on the stems, and the much finer vein structure of the leaves.
This striking plant, hybridized from three other Pieris species, is
exceptional, both for the colouration of its new growth, and its
unusually shaped strands of flowers. The incredible strength of
the fragrance of the blooms should also be mentioned. The car
windows were closed to protect the plant while driving home from the
greenhouse, and the waves of fragrance were almost suffocating!
The macro-photographs were taken with an eight megapixel Canon 20D DSLR
equipped with a Canon EF 100 mm f 2.8 Macro lens which focuses to
1:1. A Canon 250D achromatic close-up lens was used to obtain
higher magnifications in several images.
The photomicrographs were taken with a Leitz SM-Pol microscope (using
dark ground and phase-contrast condensers), and the Coolpix 4500.
A Flower Garden of
A complete graphical index of all of my flower articles can be found here.
The Colourful World of Chemical Crystals
A complete graphical index of all of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the
September 2008 edition of Micscape.
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