A Close-up View of the

Italian Heath Plant

Erica ventricosa

by Brian Johnston   (Canada)

The spectacular flowers, and compact habit of this shrub make it an ideal houseplant or landscaping addition.  Although the plant is sold at my local garden centre as ‘Italian heather’, it is in fact a member of the Ericaceae family – genus Erica.  Heathers are identified by the genus Calluna.  Both are low evergreen shrubs, however heaths have needle-like leaves, while heathers possess short, scale-like, overlapping leaves.  Italian heath’s species name ventricosa is derived from the Latin ventricosus which refers to the inflated or swollen shape of its flowers. 

From a distance, the plant definitely catches ones attention with its tightly packed attractive leaves, and multitude of buds and flowers.  When viewed close-up however, its truly remarkable characteristics are revealed.  The main reason for this is that its flowers are relatively small, about 15 mm in length.  The first image in the article shows such a close-up view.

For comparison, here are two views of the plant from a distance.

Many strong vertical branches carry huge numbers of bright green, shiny leaves.  Intermingled with these leaves are large numbers of white buds, and flowers with bright pink tips.  No matter when you look, each branch has both buds and flowers.  As buds bloom, new buds appear almost as if by magic!

Let’s look at the blooming process of the Italian heath.  Very early stage buds are pale green or white in colour, and are almost completely obscured by the whorl of long, narrow, green sepals that form the calyx.

These sepals can be seen more clearly in the two images below.  Notice that the sepals’ tips are brownish-red in colour.

As time passes, the buds increase in length until they are longer than the sepals.  At this stage, their only colouration is an extremely faint pink band below their tips.

Next, the tip of each bud increases slightly in size above the band mentioned above, and it takes on a deep pink colour.

Finally the four petals that previously formed the bud’s tip open out to form the star shape of the top of the flower.  The overall appearance the flower is remarkably similar to that of an urn which tapers to a narrow throat and flares to four pointed lobes.

If one of these pointed lobes is examined under the microscope, it is seen to possess a number of slender, white, hair-like structures growing along its edge.

The photomicrographs below show the cellular structure of the body of the lobe (left), and its edge (right).

A view directly into the front of the flower shows hints of the yellow pollen covered anthers positioned at the level of the narrowing in the tube.

If the urn-shaped flower tube is grasped carefully by the lobes, and pulled gently while holding the base of the sepals, it is possible to completely remove the tube leaving the reproductive structures untouched.  A single pistil and numerous stamens are visible.  Note that the stigma is positioned at the same height as the midpoint of the anthers.

Before blooming, the flower’s anthers are busy producing pollen within their interiors.  At some point they begin to release this pollen, a process called dehiscing.  In the case of Erica ventricosa, pores open in the sides of the anthers through which the pollen escapes.

The image below shows that each anther consists of two lobes.

Photomicrographs follow that show the two mirror image lobes, and their prominent pollen releasing pores.

Higher magnification photomicrographs show a pore, and the edges of anther lobes in more detail.

As mentioned before, the flower’s stigma is positioned precisely at the same level as the pollen releasing pores of anthers.  This seems strange since this would promote self-pollination.  It is possible that, as in some other species, the flower’s stigma is not receptive to its own pollen.

Both macro and micro views of a flower’s pistil can be seen below.  Note that in the previous two images the supporting style is yellowish-green, while here it is bright red.  The earlier images are from a newly opened flower whereas these are from a mature flower.  The stigma itself is dark, almost black in colour.

The leaves of this plant are described as ‘typically ericoid’, which means that they are small, narrow, and pointed.  In addition, they are covered with colourless hairs, and especially near the tip, have a distinctive, deep groove on their outer surface.

Photomicrographs show this groove, and the many surface hairs more clearly.  The last three images show that the interior of each leaf, near its tip, is actually hollow, and that the interior is completely covered with short hair-like protuberances.

Here are two views showing branches near the base of the plant.  Strangely, these leaves do not have the groove mentioned earlier.  It seems as though the grooved leaves occur only beneath flowering tips of branches.

The lack of a groove is evident in the first of the photomicrographs below.  The second and third show views of the hairs that cover the leaf’s surface.

One description of Italian heath that I read describes the shrub as being “well-branched”.  This is certainly true, as can be seen in the following image.  The wood itself is very tough and difficult to cut.

Italian heath’s flowers have, as we’ve seen, a very attractive shape.  What is not evident in photographs is that they possess the ‘look’ of fine porcelain, and that the have a shiny wax-like texture when touched.  They truly are spectacular!

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.

A 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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