A Close-up View of the

"Japanese Pieris"

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 chains.

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 arrangement.

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 leaflet’s surface.

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!

Photographic Equipment

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 Macroscopic Delights

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.

 All comments to the author Brian Johnston are welcomed.

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