Although I had recently photographed a blue hybrid lupine, seeing this strikingly colourful plant at my local greenhouse provided a temptation that could not be resisted.  I am constantly struck by the freshness and beauty of this species.  The plants look remarkably healthy, with unblemished leaves and colourful flower-spikes, and they are a pleasure to photograph.  No flimsy waving or vibrating stalks here, at the mercy of every breath of the photographer, or passing truck!

In North America, the common name of the genus is spelled lupine; elsewhere it is lupin.  Both spellings are correct.  Most members of this family, often called the ‘bean’, ‘pea’, or Fabaceae family, can ‘fix’ nitrogen from the atmosphere into compounds which fertilize the soil.  On its roots there are nodules which contain symbiotic Bradyrhizobium soil bacteria.  Strangely, it was once believed that lupines decreased or ‘wolfed’ the soil’s fertility.  Both the common and genus name were thus based on the Latin ‘lupus’, which translates to wolf.  Although the plant is very beneficial to the soil, its seeds are certainly not a good food for grazing animals.  Lupinine, an alkaloid, is the major poison, but the plants also contain dangerous enzyme inhibitors.

The first image in the article shows a section of the 80 centimetre high plant photographed for this article.  What a remarkable transformation occurs as a bud-stage flower-head develops into the mature bloom seen below.


The process begins with a tiny 1.5 centimetre high bud, and its associated leaflet.  Absolutely no hint of the flower-head’s final colouration is apparent at this stage.


Overlapping pale green sepals protect the underlying immature flowers.  Note the paw-like shape of the nearby leaflet.



Higher magnification of the leaflet reveals that its surface is covered by a mass of fine, colourless hairs that make it soft to the touch.


Another view shows that the overlapping sepals on the flower-head are exceedingly hairy as well!


As the flower-head grows, its length increases faster than its diameter, which results in a cone-shaped structure.  At the base of the cone, hints appear as to the final flower colour.


Closer views of this early stage can be seen below.  Notice in the image on the right, that the underlying pink petals, as they increase in size, have pushed aside the associated green sepal.


In the middle section of the cone, only the overlying sepals are visible.


A flower-head blooms from the bottom up.  The image that follows shows the very start of this process as the growing pink flower pushes aside its clasping sepal.


Over a period of about a day, more and more sepals are displaced by growing, immature flowers.  The sequence of images that follows, (taken with increasing magnification), shows this developmental stage.




At the transition zone, both petals and their associated sepals have a pinkish-red colouration.


Still later, the first flowers to bloom, (at the base of the flower-head) have grown away from the main stem on the ends of their supporting stalks.  At this stage the sepals that were the predominant visual structure, have been replaced by the flowers themselves.


Higher up the flower-head, only the tips of the flowers have developed a red tint.


Note in the two images below, that the breadth of the lupine’s flowers increases as they develop.


Front and side views of an immature flower can be seen below.  Notice on the right that the sepal size is small compared to the flower bud that it formerly enclosed.  Eventually all of these sepals turn brown, shrivel, and drop from the plant.


Here is a sequence of images that shows the middle section of a flower-head when the deep red colouration has almost encompassed the entire structure.  In all of the images notice that in some of the lower flowers the two side petals have split apart to reveal a lighter pink interior.



In the lower part of the flower-head on the left below, lupine flowers have reached their mature appearance.  A closer view of one of these flowers can be seen on the right.


Even at this late stage, the flower-head’s tip is as immature as the bud-stage shown at the beginning of the article.


In contrast, the central section is in full bloom.


Individual flowers are supported by narrow diameter stalks connected to the main stem.


Lupines possess the ‘typical’ pea-flower shape.



Consider the flower just to the right of centre, at the bottom of the image that follows.  The large oval petal at the flower’s top is called the banner.  In the flower immediately above, the two halves of the banner are folded down on both sides of a structure formed by the wings of the flower.  In the flower at the top of the image, the folded banner is tightly in contact with the wings.  More detailed views will show these structures more clearly later in the article.


In the four images that follow, the banner has folded way back on both sides.  This is the final look of a lupine flower.



The side view of a flower shows the banner at its top, and one of the two wings that enclose its reproductive structures.


Enlarged images of a wing can be seen below.  The one on the left is pristine, but the older one on the right has evidence of some sort of blight.


Several images follow that show the striking contrast between the colourful blooms, and the plant’s dark green leaves.




The two wings positioned beneath the flower’s banner are separate entities that appear to form a container with no openings.


Close examination of the flower shown here reveals a gap that has formed at the top front of the wing container.


If one of the wings is removed, a strangely shaped structure called the keel is revealed.  Both the flower’s stamens and pistil are contained within this keel.


In fact, if you look closely, you can see the bright yellow pollen grains within the keel.


Beneath the keel is one of the sepals mentioned earlier in the article.


The sequence of three images below, taken with increasing magnification, shows the top of the keel, and bright yellow pollen grains that adhere to it.  When an insect alights on the wings of the flower, pressure is applied to the keel.  This pressure causes the top of the keel to separate into its two separate sections, leaving a gap or opening.  One of the insect’s appendages, or part of its body can then come into contact with the constituents of the keel container – pollen covered anthers and stigma.



In the following image, the two sections of this keel container have been removed to show the contents.  A single long pistil is visible, as are a number of stamens.


Here both wings and keel have been removed.


The first image below shows that stamens come in two lengths – short and long.  The upward curving pistil is also visible in this image.  The remaining three images show higher magnification views of pollen encrusted anthers and their supporting filaments.




Views of a flower’s pistil, with the stigma supported by the style, can be seen below.


Here is what a flower-head looks like about a week after the bud stage.  It is a view well worth waiting for!


Next we’re going to look at lupine leaves.  The leaflets, to start, are packed together as shown below.


As the leaves open, it is apparent that the approximately 12 leaflets are arranged in a fan shape.  This shape is referred to as digitate (like the fingers of a hand).  Now that the leaflets have fanned out into their final positions, there is one more development that must occur. The leaflets have been folded in half lengthwise, and they must unfold.


The images that follow show the appearance of the mature leaves.






Each leaflet is joined to the main stalk by its extremely prominent under-surface vein.


The leaflet’s under-surface is liberally covered with fine hairs.


Finally, here are some additional views of the very large potted plant that was the subject of this article.






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.


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.