A Close-up View of a Hybrid Stonecrop

Sedum x hybrida 'Sunkissed'

by Brian Johnston   (Canada)

“The yellow stone-crop suffered to take root
Along the window’s edge, profusely grew,
Blinding the lower panes.”

William Wordsworth

Characteristics such as attractive appearance, and considerable hardiness, make members of the Sedum genus popular landscaping plants.  The common name Stonecrop is from Middle English, and literally means “sprouting from the stone”.  This refers to the fact that the plant prefers good drainage, and is therefore found growing amongst stones in the wild.  The genus name Sedum is from the Latin sedere, which translates to ‘sit’, another reference to the plants ‘sitting’ on stones.  Other experts believe that the ‘sit’ refers to their low spreading habit, while still others translate ‘sedere’ as ‘to quiet’ and refer to the plants’ supposed sedative properties!

Sedums are members of the Crassulaceae family, where this name is derived from the Latin root word for ‘thick’ or ‘dense’.  This refers to the fact that its members are succulents which possess water-storing leaves.  It is these leaves that provide much of a Stonecrop’s visual appeal, since its many flowers are relatively small.

The particular Stonecrop hybrid studied in this article, Sedum ‘Sunkissed’, was about 50 centimetres in height, and possessed white flowers with contrasting red anthers.  As you can see from the images that follow, the flowers do not provide an initial visual impact.

On the other hand, even from a distance, its unusually shaped thick leaves, positioned in spiral fashion around the stem, may prompt a second look.

The leaves grow directly from the stem with no stalk, and are thus referred to as clasping.  Both its major vein, and its serrated edge are tinged with red, adding to the visual appeal.

Leaves form an acute angle with the stem.  Secondary veining exists, but it is certainly not prominent.

Closer views reveal that a leaf’s upper surface has randomly positioned tiny red spots.

When leaves die and fall from the stem, they leave behind distinctive scars.

Strangely, the stalk that supports a new bud-stage flower-head grows from the point of connection of a leaf to the stem (the leaf axil).

New buds have a pentagonal shape when viewed from above.  Notice an opening bud in each image.

The four images that follow show a blooming flower-head.  Only the red anthers provide any real colour.

Each flower has five petals, and its centre is filled with five pie-shaped, light green ovaries.

Careful examination of the three images that follow reveals that some of a flower’s anthers are red, and approximately oval in colour, while others are yellowish brown, and more irregular in shape.

The larger red anthers are not yet releasing their pollen.  It appears as though they are covered by protective membranes that eventually disintegrate to reveal the pollen releasing structures.

One of these colourful membranes can be seen in the two photomicrographs below.

Each of the anther’s lobes appears to split longitudinally in order to expose its pollen – a process referred to as dehiscing.

Photomicrographs showing an intermediate stage in this process can be seen below.

Stonecrop pollen grains appear roughly ellipsoidal in shape.

There are few interesting details at the tips of the flower’s pistils.

Even under the microscope, the usual hair-like protuberances present on the receptive upper surface of the stigma, are missing.

If one of a flower’s ovaries is split open in order to reveal its contents, the developing seeds can be seen.

The ridged outer surface of the ovary can be seen in the photomicrograph below.

While photographing the flowers of this plant, I noticed considerable activity on the surface of anthers.  Closer inspection revealed that the pollen seemed to be the food of this extremely small insect.  Whether there to feed on pollen grains, or to suck fluid from the anther itself, this little creature became coated in the pollen grains as it moved from anther to anther.

There are approximately 600 species of Stonecrop, most of them growing in the Northern Temperate Zone.  Based on the number of Stonecrop plants in my neighbours gardens, they certainly are popular!

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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Published in the July 2011 edition of Micscape.
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