View of a Hybrid Yarrow
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
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
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.
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
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
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
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
Europe and Western Asia. Today it grows in temperate regions
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
A Flower Garden of
A complete graphical index of all
of my flower articles can be found here.
The Colourful World of
A complete graphical index of all
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the June
2011 edition of Micscape.
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