A Close-up View of the Wildflower

 "Red Clover"

(Trifolium pratense)

by Brian Johnston   (Canada)

The red clover plant is so common that I suspect most people simply accept its presence in the environment, and seldom take a second glance at this small, but colourful wildflower.  In fact, up - close, the red clover is a thing of great beauty - not only for its striking colouration, but for the uniqueness of its form.  My hope is that the images in this article provide the impetus for you to uproot a plant and have a close look at one of our most ubiquitous wildflowers!

I am constantly on the lookout for information about the wildflowers that I macro-photograph.  Occasionally, I find a particularly obtuse description, that is “meaty” in the scientific sense, but distinctly lacking in the transference of information to the uninitiated.  One of the “best” that I have found refers to the blooms of the red clover.

“….heads mostly terminal, sessile, short-peduncled, usually closely subtended by the stipules of the upper pair of leaves, dense, subglobose to ovoid, 1.2–3 cm long; flowers sessile, 10–15 mm long, rosy purple to creamy-white, erect; calyx-tube campanulate, narrower at base, 10-nerved, pubescent including the inner margin of the throat,.The teeth filiform from a triangular base, sparsely hirsute, porrect, the upper about equaling the tube, the lower almost twice as long; corolla about twice the length of the calyx….”

If the above is perfectly clear to you, perhaps you might want to skip to another Micscape article.  This article is based more on the concept of a “picture being worth a thousand words”.

Red clover belongs to the Fabaceae family, (previously called the Leguminoseae family), which has many members, including the peas, beans and peanuts.  Family members have the ability to take nitrogen from the atmosphere, and with the aid of soil bacteria, make it available to other plants.  The process is called “nitrogen fixation” and is very important to the agricultural industry.

All red clover flowers have a purple-pink colour, but there is considerable variation in the intensity of this colouration.  The images below show a particularly colourful flowerhead.  The bloom, (about 2.5 cm in diameter), is composed of up to one hundred individual flowers called florets.  The images show the main distinguishing characteristic of the species - oval leaflets with a prominent white “V” mark in the center.  This marking is called a chevron.  Notice also that the stem and leaflets are intensely hairy.

The characteristic chevron markings on the leaflets can be seen even more clearly in the two images of red clover buds.  It is unusual to find a specimen as perfect as the one on the right.  It is also unusual (and supposedly lucky), to find four leaflets instead of the normal three!  (The genus name Trifolium translates to “three leaved”.  The species name pratense translates to “meadow”.)

As the flowerhead begins to bloom, florets open in order from top to bottom.

The irregular edge of a leaflet’s chevron is evident in the high magnification photograph below.

Floret density in the flowerhead is also variable.  Some heads, like the one on the left have florets spaced far enough apart, that the underlying structures can be seen.  Others, like that on the right, are packed solid with florets.  (Men often show the same variation in scalp hair density.  Unfortunately, my head now bears a greater resemblance to the flowerhead on the left than to that on the right!)

A closer look reveals the structure of individual florets.  The upper-most petal has a noticeable vertical groove.  This petal forms the “banner” or “standard” of the flower.  Beneath the banner are two lateral petals referred to as “wings”.  It is these wings that cause the flower’s structure to be called papilionaceous, (like a butterfly).  Finally, beneath the wings are two petals joined to form the “keel”.  This keel encloses the reproductive structures of the flower.

Immediately beneath the flowerhead, there are usually three green bracts (modified leaves) with an intricate two-shaded green pattern.  These bracts abruptly taper to a slender tip.  Many hair-like green projections or rods, which themselves are covered with finer hairs, can be seen growing up between the tubular bases of the florets.

Viewed from beneath the flowerhead, these bracts are very attractive.  Notice that all surfaces are covered with long fine white hairs - particularly the stem.  (The stem is more properly called the peduncle.)

Occasionally, as in the bloom shown below, the bracts are some distance down the peduncle.  This allows a clearer view of the hairy green projections between florets.

The images below reveal the dark red vertical stripes that decorate the banner petal of each floret.

Higher magnification reveals a common problem that occurs in the macro-photography of small objects
like the florets of the red clover.  Even using the minimum aperture of the Sony F-828 camera, (f 8), the depth of field is still insufficient to keep all parts of the floret in focus simultaneously.  (The section of each floret that can be seen in the photographs is about 4 mm long.)

If the two petals forming the “keel” of the floret are removed, the reproductive structures hidden beneath are revealed.  Ten brown anthers atop pale green filaments surround the single stigma, and the style that supports it.  The anthers are the male pollen producing organs, while the stigma is the female pollen accepting organ.

A closer view of an anther, using a microscope, reveals its triangular shape.  Several pollen grains can be seen on its surface.

The stigma also has pollen grains adhering to its surface.

A much higher magnification shows that each grain is roughly ellipsoidal in shape and has a longitudinal groove.  The surface is not smooth.

I mentioned earlier that the intensity of colour varies in red clover plants.  Notice the paler shade in the bloom on the right.

Several additional images of this lighter bloom follow.  It is interesting to note in the second image, that the florets have bloomed from bottom to top.  Many unopened florets are visible at the top of the flowerhead (facing the observer).

Even higher magnifications reveal the long tubular bases of the florets.  Notice that the stalks between florets are red-brown in this flowerhead.

A much higher magnification of one of the stalks shows it to be covered with white hairs.

Other similar stalks in a different flowerhead are green, and spotted with red.

Finally, here are three additional images of this extremely common wildflower.

I can remember as a child, pulling bunches of red clover florets from a flowerhead, and sucking on the tubular ends to taste the sweet nectar.  Today, I am older and wiser.  Examining flower parts under the microscope has revealed the many animal denizens, invisible to the naked eye, that inhabit flowers.  The thought of swallowing these creatures has taken all the fun out of such activities - a perfect example of the innocence of youth!

Photographic Equipment

The majority of the photographs in the article were taken with an eight megapixel Sony CyberShot DSC-F 828 equipped with achromatic close-up lenses (Canon 250D, Nikon 5T, 6T, Sony VCL-M3358, and shorter focal length achromat) used singly or in combination. The lenses screw into the 58 mm filter threads of the camera lens.  (These produce a magnification of from 0.5X to 10X for a 4x6 inch image.)  Still higher magnifications were obtained by using a macro coupler (which has two male threads) to attach a reversed 50 mm focal length f 1.4 Olympus SLR lens to the F 828.  (The magnification here is about 14X for a 4x6 inch image.) A few of the photographs were taken with an eight megapixel Canon 20D DSLR equipped with a Canon EF 100 mm f 2.8 Macro lens.  The photomicrographs were taken with a Leitz SM-Pol microscope (using a dark ground condenser), and the Coolpix 4500.


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.

 All comments to the author Brian Johnston are welcomed.

Microscopy UK Front Page
Micscape Magazine
Article Library

© Microscopy UK or their contributors.

Published in the June 2006 edition of Micscape.
Please report any Web problems or offer general comments to the Micscape Editor.
Micscape is the on-line monthly magazine of the Microscopy UK web
site at Microscopy-UK  

© Onview.net Ltd, Microscopy-UK, and all contributors 1995 onwards. All rights reserved. Main site is at www.microscopy-uk.org.uk with full mirror at www.microscopy-uk.net .