The classifications listed came from Gray's Botany of the Northern United States. Achillea millefolium was named by Linnaeus. (I am not sure where the holotype of this species is, but Reed Crook suggested that it might be in the Linnaean Herbarium.)
Class: Dicotyledonous
Subclass:
Angiospermae
Order: Compositae
Suborder: Tubuliflorae
Family: Compositae
Genus: Achillea
Species: A.
millefolium
Description: According to Harned, this is the largest family of flowering plants. There are over 10,000 widely distributed species of this family. Most are herbs with compound flowers, and florets arranged in tight heads upon a common receptacle. They usually have 5 stamens with their anthers rolled into a tube around a style. The limb is made of bristles, scales, or teeth (Harned, 1936).
Identification: The following key is presented by Harned in Wild Flowers of the Alleghanies. However, this key has been shortened to strictly serve as a method to identify plants as members of the family Compositae.
A. Plants reproducing by seeds each containing
an embryo.
B. Ovules and
seed exposed on unclosed bracts; trees and shrubs
(Gymnospermae)
B. Ovules and
seeds contained in an enclosed ovary; herbs or woody
plants (Angiospermae)
C. Plants without true stems and leaves...Lemnaceae
C. Plants ordinary, leafy.
D. Ovary inferior.
E. Herbs, rarely somewhat woody at base.
F. Leaves alternate or basal.
F. Leaves opposite or verticillate.
G. Flowers in umbels...Araliaceae
G. Flowers in involucrate heads.
H. Stamens separate or slightly united.
H. Stamens syngenesious...Compositae
Description: Gray describes members of the genus Achillea as having heads with many flowers. The rays are few and fertile. The involucre is inimbricated. Receptacles are chaffy and flat. Achenia are oblong, flattened, and margined. Pappus are absent. These plants are perennial herbs with small corymbose heads (Gray, 1848).
Identification: Harned presents this key for identifying the genus Achillea (from other genera in the family Compositae) in Wild flowers of The Alleghanies. However, this presentation of the key has been modified to serve as a method for identifying a member of the genus Achillea.
1. Flowers of the head tubular, or only
the marginal ones ligulate; juice not
milky
2. Involucre of the
pistillate flowers closed and woody; heads unisexual,
not radiate, the staminate and the pistillate heads very different in
appearance.
2. Involucre not closed
or woody.
3. Heads without rays.
3. Heads with ray and disk flowers.
4. Pappus of awns.
4. Pappus of scales, which are sometimes deciduous.
4. Pappus capillary, receptacle not chaffy.
4. Pappus none or a mere crown.
5. Receptacle not chaffy; rays white or pinkish
5. Receptacle chaffy.
6. Rays yellow.
6. Rays white.
7. Heads large, 13-30 mm in diameter; achenes
terete...Anthemis
7. Heads small, 3-7 mm in diameter; achenes
flattened...Achillea
Description: These
plants have erect stems that are about 12-30 inches tall. However,
if the plant is sprayed continuously with salt water and coastal winds
it will be shorter (Horn, 1993). The stem is strong, upright, ridged,
and covered with soft woolly hairs. At the top of the stem, flowers
grow grow together in flat heads (Carey, 1950). The leaves are strongly
scented and divided into many small segments. The head is made up
of white or pink flowers. The center of the head is composed of small
tubular flowers (Horn, 1993).
Identification: The Appalachian Mountain Club's Field Guide to Mountain Flowers of New England provided this scheme for identifying similar species within the genus Achillea. There are several characteristics that can be used to distinguish between these plants. Achillea millefolium has a stem that can range from smooth to cobweb-like, whereas A. lanulosa has a heavily woolly stem. Both of these species have involucral bracts that are colorless to light brown. A. borealis has dark brown to black margins on the involucral bracts. It also has fewer leaves on its stem (Appalachian Mountain Club, 1977). A. ptarmica and A. sibirica can be separated from A. millefolium because their leaves are subentire, serrate, or incised. They are never pinnatifid. The leaves of A. millefolium are pinnately-dissected and have narrow rachis (Scoggan, 1979).
The success of this plant can
be credited to fact that it inhabits neglected patches of the earth, can
tolerate droughts, and has a long blooming season. The long blooming
season helps the plant to avoid competition for insects (Blanchan, 1901).
Insects cross-fertililize Achillea millefolium by crawling over
the clusters of disk-florets (Harned, 1936). For this reason, the
plant uses most of its energy on flower production (Blanchan, 1901).
The plant can reproduce by vegetative and sexual means (Kannangara, 1985).
Vegetative spread is rapid, and seed reproductive allocation is low.
Most races of this species (in North America) are tetraploid and hexaploid.
Conditions for germination are optimal when seeds are exposed to continuous
light and are sown on the surface of the soil (Warwick, 1982). Experiments
have shown that these seeds can germinate after chilling, coat pricking,
exposure to high nitrate concentrations, and temperature alterations (Kannangara,
1985). In the winter, the herbs tend to be dormant. They survive
on carbohydrates that are stored in the plant's roots. During mild
winters, the plant can retain some of its leaf content (Warwick, 1982).
The herb grows in a wide variety
of climates and habitats because of its deep root system. This feature
allows the herb to adapt to many soil types of different moisture concentrations.
A plant with a lower moisture concentration in its soil will usually have
smaller leaves and flowers than a plants that has very moist soil.
Its branched rhizome system provides a means for the plants to spread
laterally. They spread about 7 to 20 cm per year. (Warwick,
1982). It is commonly found from late spring to fall (Newcomb, 1977).
A specimen in the University of Georgia Herbarium was found in Walton County,
GA on April 25, 1992. It was collected along Highway 81 near the
Appalachee River. A more recent specimen (also in the UGA Herbarium)
was found in Rabun County, GA on June 1, 1996. This species is very
common throughout Georgia. In very dense situations, the majority
of the plants are vegetative and do not produce flowers. Of the plants
that do produce flowers, most of them do not produce seeds. The populations
are regulated by seed production, mortality, and plasticity (Warwick, 1982).
The herb can be used for many
things. In Sweden, it is used to make an extremely intoxicating beer
(Harned, 1936). It is put in bridal wreaths because the maidens wearing
them are believed to possess a mystical charm relative to their married
life. However, some people used to believe that the herb could induce
nosebleeds (Blanchan, 1901).
Life
Cycle and Habitat
Order
Achillea millefolium
Achillea millefolium is often found in recently disturbed areas such as open, dry fields (Kricher, 1988). It can also be spotted quite frequently along banks and roadsides (Blanchan, 1901). It inhabits wastelands throughout North America (Dean, 1973). Physical conditions should be variable and extreme (Kricher, 1988).
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The genus Achillea was
named for the Trojan warrior, Achilles, because he was the first to discover
the healing virtues of the plant. He used the herb to heal
the wounds of his soldiers (Carey, 1950). In ancient Greece, the
plant was thought of as a witch's herb that could be used to make a tea
that could cure various ailments (Orr, 1974). Oils from the plant
are ingredients in home remedies for coughs, bladder disease, kidney disease,
and stomach ailments. The leaves of the plant can be used in salads
and soups. They can also be used as a tobacco substitute. The
roots were used as an anaesthetic to relieve toothaches (Warwick, 1982).
Achillea millefolium
contains potential allergens that can cause irritations, rashes, allergic
contact dermatitis, and eczema (Tampion, 1977).
Medical Uses
Everything
You Need to Know
1. Appalachian Mountain Club. 1977.
Field Guide to Mountain Flowers of
New England.
Appalachian Mountain Club. Boston, MA
2. Batson, W.T. 1984. Genera
of the Plants of Eastern North America.
University of South
Carolina Press. Columbia, SC
3. Blanchan, Neltje. 1901. Nature's
Garden. Doubleday, Page & Co. New
York, NY.
4. Carey, M.C. 1950. Wild
Flowers at a Glance. Pellegrini and Cudahy.
New York, NY
5. Dean, B.E., A. Mason, and J.L. Thomas.
1973. Wildflowers of Alabama
and Adjoining States.
University of Alabama Press.
6. Gray, A. 1848. Botany
of the North American United States. James
Munroe & Co.
London
7. Harned, Joseph E. 1936. Wild
Flowers of the Alleghanies. Press of the
Sincell Printing Co.
Oakland, MD.
8. Horn, E.L. 1993. Coastal
Wildflowers of the Pacific Northwest. Mountain
Press Publishing Co.
Missoula, MT
9. Kannangara, H.W. and R.J. Field.
1985. Weed Research. Blackwell
Scientific Publications.
Oxford.
10. Kricher, J.C. and G. Morrison.
1988. A Field Guide to Eastern Forests.
Houghton
Mifflin Co. Boston, MA
11. Newcomb, L. 1977. Newcomb's
Wildflower Guide. Little, Brown and
Co.
Boston, MA
12. Orr, R.T. and M.C. Orr. 1974.
Wildflowers of Western America.
Chanticleer
Press, Inc. New York, NY
13. Radford, A.E., H.E. Ahles, and
C.R. Bell. 1968. Manual of the Vascular
Flora
of the Carolinas. University of North Carolina Press. Chapel
Hill, NC.
14. Scoggan, H.J. 1979. The
Flora of Canada. National Museum of Natural
Sciences.
Ottawa.
15. Tampion, J. 1977. Dangerous Plants. David & Charles. England.
16. Torrey, John. 1838. A
Flora of North America. Wiley and Putnam. New
York, NY
17. Warwick, S.I. and L. Black. 1982.
"The Biology of Canadian Weeds."
Canadian
Journal of Plant Science. Agricultural Institute of Canada.
Ottawa.
I would like to express thanks to:
Reed Crook for his help in the University of Georgia
Herbarium
Morgan Smith for scanning images