A Close-up View of Little Princess Spirea


A Close-up View of "Little Princess" Spirea

Spiraea japonica 'Little Princess'

by Brian Johnston   (Canada)

This plant is a hybrid of Japanese Spirea which is native to Eastern Asia.  The native plant, first brought to North America in the 1870’s, is a small deciduous shrub that grows to about 2 metres in height.  By contrast, the hybrid Spiraea japonica ‘Little Princess’ barely reaches 0.5 metres at maturity.  Although small in stature, “Little Princess” Spirea certainly puts on a colourful display during late spring and early summer.  Its bright red and pink flowers, each less than a centimetre in diameter, are held in almost flat clusters referred to as corymbs.  One such corymb can be seen in the first image in the article.

Other views of the plant, showing its variously shaped corymbs, and the emerald green of its lance-shaped (lanceolate) leaves, can be seen below.

A new growth shoot is shown in the following images.  Notice that its leaves are a slightly lighter green, and that a number of bud-stage corymbs are visible.

Spirea buds are almost perfectly round, and as can be seen in the image on the right below, are protected by a ring of light green sepals (modified leaves).

Some, but certainly not all of the bud clusters, are associated with a leaflet.  The one shown in the image below has not completely unfurled.

As the time for blooming approaches, the five green sepals begin to be pushed away by the swelling petals that make up the flower’s corolla.  The brilliant red colour of the corollas makes a startling contrast with the deep green of the surrounding foliage.

Closer views of the opening buds reveal the strange thread-like fibers that run between the edges of adjacent sepals.  These threads obviously break when the enlarging corolla pushes the sepals far enough apart.

Notice the intense hairiness of the bud stalks, and the fused base of the sepals.

The images below show buds that are hours from blooming.  Notice that at this point, the sepals have opened into 5-pointed stars.

In a given plant, the flower clusters display a wide range of developmental stages.

A view from beneath the flower-heads reveals the very light green stems of the plant.

Each blooming flower in the cluster sends out a spray of stamens, longer than the diameter of the flower itself.  The multi-lobed pistil on the other hand, barely protrudes above the corolla’s rim.

As the magnification increases, it is eventually possible to get a better look at the anthers on the ends of a flower’s exceedingly spindly filaments.  It is also evident that the anther’s possess two lobes.

The photomicrograph on the right below shows a portion of a flower’s petal.

A higher magnification reveals its cellular structure.

Near the base of a petal, cells contain darker spots of unknown origin.

Another area of the petal is coated with ellipsoidal Spirea pollen grains.

Let’s look more closely at a flower’s anthers.  To begin, an anther is covered by what appears to be a pinkish-red membrane.

This membrane disintegrates over a period of several days to reveal the amazingly smaller, pollen covered anther beneath.

Three photomicrographs showing the surface of the intact membrane can be seen below.

After the membrane has disintegrated, the anther looks like this.

In the image below there is a very dark red ring at the flower’s centre.  This ring is composed of the bases of the flower’s five petals.  On the right is a photomicrograph of one of these bases showing its dark red rectangular lobes.

Three higher magnification images show these lobes in more detail.  (The red radial structures on the right in the first two images are filaments.)

The area further up the corolla from the base has many seemingly transparent hairs growing from the surface.

A flower’s stigma appears to have four lobes.

The cellular structure of the top of the supporting style can be seen in the images that follow.

A Spirea leaf is prominently veined and has small, irregularly shaped, pointed lobes.

The undersides of leaves are much lighter in colour, and the raised veining is more prominent.

Views of the top and bottom of a leaf follow.  The combination of the raised veins, and much finer pattern between them makes for an extremely attractive leaf.

Higher magnification shows the subsidiary veining more clearly.  Notice the interesting tiny white dot at the tip of each of the leaf’s lobes.

The shape of these lob tips varies dramatically!

Photomicrographs of the subsidiary veining shows the random nature of the pattern more clearly.

Here, the strange shape of the cells that compose a vein is shown.

In some areas, exceedingly long fine hairs grow from the surface of a vein.

Spiraea japonica ‘Little Princess’ is a perfect example of an “ornamental” plant.  It continues to be interesting no matter how closely you examine it!

Photographic Equipment

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 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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