A Close-up View of a Hybrid Yarrow

Achillea millefolium 'Apple Blossom'

by Brian Johnston   (Canada)

Although the cultivar studied in this article has more colourful flowers than the Common Yarrow, it shares most of its characteristics.  Yarrows in general are perennial plants that produce several stems from a rhizome.  Their leaves are evenly distributed along the stem, with the largest at the base of the plant.  Fern-like, the leaves are grayish-green, woolly and lance-shaped (lanceolate), with the margins deeply dissected.

The genus name Achillea was assigned by the father of botanical nomenclature, Linnaeus.  Achilles, the Greek hero of the Trojan War in Homer’s Iliad, used Yarrow to treat his soldier’s wounds.  Millefolium, the species name refers to the plant’s many leaves (thousand leaves).  Down through recorded history, Common Yarrow has had a reputation for having medicinal properties.  It is probably for this reason that it has a plethora of common names including arrowroot, bad man’s plaything, yarroway, woundwort, thousand seal, stanch weed, snake’s grass, seven year’s love, sanguinary, old man’s pepper, old man’s mustard, nosebleed, noble yarrow, millefoil, milfoil, milefolium, hundred leaved grass, field hops, eerie, devil’s nettle and death flower!

The images that follow show an Achillea millefolium ‘Apple Blossom’ plant in the bud-stage.  Each flower-head is a slightly dome-shaped cluster of flowers, (or buds in this case).  In reality however, each bud opens into a composite flower-head which contains both ray and disk flowers.  This means that the ‘large’ flower-heads are composed of ‘small’ flower-heads, which in turn contain the ray and disk flowers.  The overall height of the plant is about 30 centimetres. 

A new ‘large’ flower-head looks like a fuzzy ball when it first appears at the top of a stalk.

Closer views reveal the maze of fine threads that enshrouds the tightly packed group of very immature buds.  Even at this stage the dark, almost black edges of each composite flower’s sepals are clearly visible.

A plant’s ‘large’ flower-heads don’t mature at the same time, as is evident in the image that follows.

In the upper portion of both images Yarrow composite flower-heads have just begun to bloom.  The whorl of dark-edged sepals that surrounds each composite flower-head definitely adds to its visual impact.

In this species, a flower-head blooms by pushing its whorl of tightly packed ray petals out through the opening at the top of the ring of sepals.

The sequence of images below (taken with increasing magnification) reveals why this cultivar is so popular.  The unfurling red-edged ray petals, seen against a background of bright green leaves, are certainly photogenic!

As the ray petals begin to exit from their protective sepal enclosure, they force the tips of the sepals apart.

It is this stage, that in my opinion, is the most beautiful.  Unfortunately, as we will see later, when the composite flowers are completely mature, their colour is not as brilliant as it is here.

The next sequence of images was taken a day after the last. The ray petals now extend farther out of the whorl of sepals.

Composite flower-heads in the centre of the large flower-head shown in the sequence of images below, are now completely open.  Although they are still attractive, I still think that the bud form of this cultivar is more spectacular.  As you can see in the last few images, a Yarrow composite flower-head’s reproductive structures are extremely well hidden beneath the bases of its ray petals.

Yarrow leaves are arranged spirally around the stem.  Different hybrids have varying degrees of hairiness (pubescence), and this one is obviously at the low end of the scale.  However, its stem, which is very interesting because of its strangeness, is quite hairy.

The stem has rounded longitudinal ridges that are reddish-brown in colour.  Between the ridges are relatively flat strips that are pale green in colour.  Growing from both are very long beige coloured hairs that form a mat over the entire surface area of the stem.

Closer views reveal that there are secondary reddish-brown ridges between the principal ones.  In both images, some of the hairs have formed ‘spikes’ like those in the hair of a teenager!

Three additional images, taken with even higher magnification, show clearly that this is no ordinary plant stem!

As interesting as Achillea millefolium ‘Apple Blossom’ is, I thought that a comparison with the weed ‘Common Yarrow’ might be in order.  Images of one such example can be seen below.

This second example of a Common Yarrow plant is perfect for showing that the genus Achillea is a member of the family Asteraceae, which possesses both ray and disk flowers in a composite flower-head.  Each of the ‘flowers’ in the group is not an individual flower at all, but a group of flowers itself!

The tiny flowers in the central disk are, not surprisingly, called ‘disk’ flowers, and these have extremely small petals in a fused corolla.   If you study one of the composite flower-heads in the image below, you can see that each fused corolla in a disk flower possesses five pointed lobes.  Around the outer perimeter of the composite flower there are ‘ray’ flowers, each of which has a single much larger off-white petal associated with it.

The three images that follow show bright orange tipped tubular structures emanating from the centres of disk flowers. These are pollen covered stamens.

One of these stamens is clearly visible in the image on the left below.  The image on the right shows several pistils emanating from ray flowers.  The visible white stigmas are be bi-lobed.

The leaves of Common Yarrow are indistinguishable from those of the hybrid.

The bud stage however does not show the black edged sepals that added so much to the visual appeal of the hybrid.

Although the stem is similar in structure to that of the hybrid, it is much less colourful.

Finally, here are several photographs of still another Yarrow, this one growing wild in the grass of a nearby park.  Except for the bright red ray flower petals, the plant is identical to the weed looked at previously.

Yarrow was originally native to Europe and Western Asia.  Today it grows in temperate regions worldwide.

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.

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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