A close-up view of a lupine hybrid.

Although several lupine wildflower species are said to grow in southern Ontario where I live, I have not seen a single one! (I have looked diligently!) Out of sheer desperation, I was forced to obtain a large pot containing the hybrid blooms that are shown in this article. The large, showy spikes of blue flowers are not only extraordinarily beautiful, but also very large; a mature flower head averages about thirty-five centimetres in height.

Lupines belong to the important family of plants known as the “pea family”, or more correctly the family Fabaceae. They are also sometimes referred to as legumes. Other members of the family include the beans, soybeans, peas, peanuts and sweet peas. Many family members are cultivated as field crops, some are grown as ornamentals, and others occur as wild plants. Most legumes have nodules on their roots that contain symbiotic bacteria that convert, (or “fix”), nitrogen from the atmosphere into forms that are useful to plants. The soil in which a legume grows is actually improved!

The common name lupine, and the genus name lupinus derive from the Latin lupus which translates to “wolf”. Strangely, it was once believed that lupines decreased, (or wolfed), the soil’s fertility. In fact the exact opposite is now known to be true!

What a remarkable transformation occurs as the lupine flowerhead in bud stage develops into the final mature flowerhead seen above. At first, what appear to be pale green buds are tightly packed in a tapered cylindrical structure.

Then, near the bottom of the structure, individual, lighter coloured buds can be distinguished. If you look carefully at the right-hand image, the bottom-most ring of buds have just a hint of their final purple-blue colouration.

A closer look at this developmental stage reveals the faint hue more clearly. What is also apparent is that we have been fooled! The lower, pointed, lighter coloured structures seem to be hairless, while the upper structures are pale green, and hirsute (hairy). In fact, what appeared earlier to be buds, are actually the green, hairy leaflets that completely cover the hairless buds beneath! Several of these leaflets can be seen clasping the bottom of buds in the left image below.

The following photographs show the situation more clearly. The lupine buds have “grown out of” their fixed-size leaflet jackets. Notice in the image at left that the bottom-most buds have become deeper in colour, and that the stalks connecting them to the stem have lengthened. The leaflet at the base of each bud stalk has begun to atrophy, and turn a yellowish-brown colour. Now visible is a ring of pale green sepals (modified leaves) at the base of each bud.

After several days have elapsed, the bottom-most flowers are in full bloom, having achieved their final blue colouration.

Notice in the unopened buds located at the middle of the flowerhead, that only a narrow stripe is coloured blue, and the two “sides” of the bud are white. It also appears that the open flowers have a purplish-blue colour, while the stripe on a bud is a truer blue.

The transformation from leaflet covered bud, to exposed bud, can be seen clearly in the image below.

Newly exposed buds are striking in the subtlety of their colouration. If you look closely, you can see the small leaflets that covered the buds at an earlier stage.

Study the three images that follow to see how the white “sides” of a bud curl back to form the furrowed, white columnar structure that exists above the coloured lower section of a blooming flower. (More about a flower’s structure later.)

You may have noticed in earlier images, that the leaves of the hybrid lupine are divided into (usually) twelve leaflets. These leaflets are arranged in a fan shape that is sometimes referred to as digitate (like the fingers on a hand). At first all of the leaflets are packed together, and they slowly separate over a period of time. The image below shows this process at an early stage.

Once 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.

Here is the centre of a leaf viewed up-close after this process is complete.

Finally, the leaves are revealed in all their radial glory!

When the underside of a leaflet is examined under the microscope, oval structures called stoma and guard cells are revealed. These control the entry of gases into, and out of, the leaf. The image on the right also shows the hairs that grow from the leaflet’s underside.

Hairs growing out from a prominent vein on the underside of a leaflet can be seen in the higher magnification photomicrographs that follow.

A single lupine flower is shown below. The stalk ends in several hairy, greenish-brown sepals that enclose the flower’s base. The topmost white structure is called the banner. Beneath the banner are two veined blue wings. In the image, you can see only the one closest to the camera. A second identical wing is located behind the first. Inside the envelope formed by the two wings is the keel of the flower. The entire structure is said to have bilateral symmetry because the left and right sides are mirror images of one another.

The higher magnification image below shows the sepals more clearly.

Here is one of the wings.

Using the microscope, the cellular structure of a wing becomes visible. Notice the multi-coloured pigments that reside in the wing’s cells.

Strange pale violet bands seem to bridge the gap between the darker blue stripes.

Higher magnification reveals these bands, and also the cells making up one of the stripes.

If the two wings of a flower are removed, the keel becomes visible. The flower’s reproductive structures are contained within this keel. (Remember that the structure above the keel is the banner.)

When the keel is removed, the bright yellow anthers (male pollen producing structures) and their white, supporting filaments can be seen. Also visible is the single, very fine, threadlike style that supports at its end, the stigma (female pollen accepting structure).

Look carefully at the third image below. Five of a flower’s ten anthers are larger than the others. The pollen produced by these oversized anthers is shed into the keel, and forms a pollen mass. This mass is forced up through a pore at the tip of the keel, and onto the lower body of a bee as it lands on the flower.

Photomicrographs of an anther and its filament can be seen below. The flower’s pollen is bright yellow, and has an ellipsoidal shape.

Higher magnification reveals more detail.

Still higher magnification, using phase-contrast illumination, gives the best view of individual pollen grains.

The pistil, comprised of the thin supporting style, and “frayed” looking stigma, can be seen in the image at left below. The stigma itself can be seen in the higher magnification photomicrograph at right.

The stigma is so small that it is difficult to get sufficient depth of field to allow the entire structure to appear in focus. The image on the left shows the hair-like protuberances that help collect and retain pollen grains, while the one on the right shows the pollen grains themselves.

About one week is required for the transformation from the bud-flowerhead, seen on the left below, to the (almost) fully blooming one, on the right.

Although the bud stage is a very compact form, the constantly lengthening flower stalks make the blooming stage very large by comparison. The flowerhead’s base is typically about 12 centimetres in diameter.

This hybrid lupine produces flowerheads with extraordinary structure and colouration!

When viewed up-close, one additional detail can be seen. In the image on the right, the bottom of the white banner has a group of red spots just above the wing section. I wonder whether this is an evolutionary development to help attract bees to exactly the right spot?

The final image shows that near the end of a flowerhead’s blooming period, the flower stalks have grown so long that the bloom appears slightly straggly. In my view, earlier stages are more photogenic.

Approximately 200 lupine species are known worldwide. They have many admirers, including butterflies, bees, hummingbirds, and this macro-photographer!

Photographic Equipment

All of 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.

References

The following references have been found to be valuable in the identification of wildflowers, and they are also a good source of information about them.

Dickinson, Timothy, et al. 2004. The ROM Field Guide to Wildflowers of Ontario. Royal Ontario Museum & McClelland and Stewart Ltd, Toronto, Canada.

Thieret, John W. et al. National Audubon Society Field Guide to North American Wildflowers - Eastern Region. 2002. Alfred A. Knopf, Inc. (Chanticleer Press, Inc. New York)

Little, Elbert L. National Audubon Society Field Guide to North American Trees - Eastern Region. 2004. Alfred A. Knopf, Inc. (Chanticleer Press, Inc. New York)

Kershaw, Linda. 2002. Ontario Wildflowers. Lone Pine Publishing, Edmonton, Alberta,Canada.

Royer, France and Dickinson, Richard. 1999. Weeds of Canada. University of Alberta Press and Lone Pine Publishing, Edmonton, Alberta, Canada.

Crockett, Lawrence, J. 2003. A Field Guide to Weeds (Based on Wildly Successful Plants, 1977) Sterling Publishing Company, Inc. New York, NY.

Mathews, Schuyler F. 2003. A Field Guide to Wildflowers (Adapted from Field Book of American Wildflowers, 1902), Sterling Publishing Company, Inc. New York, NY.

Barker, Joan. 2004. The Encyclopedia of North American Wildflowers. Parragon Publishing, Bath, UK.

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