Just Yarrow?

What is the Latin name for yarrow? Achillea millefolium, most of you will answer -- everybody knows that. Unfortunately, things are less simple than they appear. There is a good deal of confusion surrounding this name, confusion that increases as time goes on. The aim of this article is to discover why this is so, what importance it has, and whether there is anything we can do about it.

Besides Achillea millefolium there are a number of other Achillea species, particularly in Europe, but also in other parts of the world. This in itself is not a reason for confusion, since there are often many species in a genus, but the fact that A. millefolium has been widely used as a medicinal plant for hundreds of years, and that it has many therapeutic applications, has made it a subject of great common interest and created ample opportunity for confusion as far as the nomenclature is concerned.


Influence of Natural Factors

Several factors are responsible for this confusion, some natural and some human. Natural factors include the following:

1. The fact that the difference between the species is often minimal, which of course can easily lead to mistaken identity.
2. The adaptability of the plant to its environment with often slight morphological changes. For the common herb collector, and certainly for those in the past, this makes it difficult to tell the species apart; many collectors were probably not even aware that there are different species.
3. There are quite a number of subspecies, often difficult to differentiate between, sometimes with a similar medicinal action, sometimes with more, fewer, or totally different actions.
4. By no means all species are used medicinally.
5. Natural crosses may occur, and these are generally very difficult to detect.
6. The presence of polyploidy. The normal chromosome number for Achillea is 9, and therefore the diploid number is 18, but apart from diploid, we also have tetraploid (2n=36), hexaploid (2n=54) and octaploid species (2n=72). Polyploidy can change a plant's chemical composition, and in the case of the Achillea species it certainly does. For instance, the volatile oil of tetraploid species contains chamazulene (up to 45-50%), while diploid, hexaploid or octaploid species contain no chamazulenes, but can have substantial amounts of à- and/or á-thujone. Apart from the composition of the oil, there may be variations in the proportions of other constituents, some of which may only occur in certain plants. Since the chromosome number cannot be determined by simply looking at the plant, but only by microscopical examination, the factor of polyploidy alone gives plenty of scope for confusion.

Influence of Human Factors

In addition to the natural factors mentioned above, two human factors have also helped to complicate matters.

The Botanist

Factor No. 1 is the botanist. Although one of the botanist's tasks is to bring order and system into the plant world, the lack of communication between botanists in different countries or regions -- at least in former times -- has often resulted in the same plant being given more than one botanical name. This has inevitably led to confusion, particularly with a plant so frequently used in folk medicine as Achillea.

Note the following passage from the Flora Europaea:

Achillea millefolium L. is a very polymorphic species in which 2 subspecies are recognised. (a) Subsp. millefolium, etc. 2n=54. Throughout the lowland range of the species. (b) Subsp. sudetica (Opiz) Weiss in Koch. The synonym in the German Flora ed. 3,2:1404 (1895) = Achillea sudetica Opiz etc. 2n=54. Mountains of central Europe...Robust plants from C. and S.W. France have been called Achillea monticola Martrin-Donos. PI. Crit. Tarn 31 (1862) 2n=72...A. inundata Kondrat. in Wissjul., Fl. RSS Ucr. 11: 553 (1962), from wet meadows in S. and C. Ukraine, may merit recognition. It is like 24(a) [Achillea millefolium subsp. millefolium] but has stems 60-100 cm;...or it is perhaps a variant of 25 [A. pannonica Scheele].

This information is in itself unremarkable -- except when taken in conjunction with other examples from the literature. The first such example is an article published in 1990, 'Achillea millefolium L. subsp. alpestris (Wimm. and Grab.) Gremli, source de chamazulene' [ 1]. In the introduction the authors mention three (!) subspecies of Achillea, and state that the subspecies alpestris is the same as A. millefolium L. subsp. sudetica (Opiz) Weiss. But the name alpestris, attributable to Messrs. Wimm. and Grab., does not occur in the Flora Europaea and is probably to be found in the French literature on Achillea. Nowhere else is this name mentioned. It is of course only a name, but the title of the article clearly states that alpestris is a source of chamazulene. If alpestris is the same as sudetica, which we know is hexaploid and thus contains no chamazulenes, obviously something, somewhere, went wrong. If, on the other hand, alpestris is tetraploid (2n=36), it can produce chamazulene, but it is then not the same as sudetica.

What is to be done? A practical first step would be to obtain some samples of subsp. alpestris, and count the chromosomes: if there are 36 it is not a subspecies of A. millefolium, and if there are 54 it cannot yield chamazulene; if it nevertheless does, we will be obliged to accept the phenomenon of 'genetic spasticity' and give up counting chromosomes in future!

A second example is furnished by Hagers Handbuch der pharmazeutischen Praxis [ 2], where, in the chapter 'Achillea', some synonyms for the different species are listed. One reads: 'A. asplenifolia Vent. = A. millefolium L. ssp. asplenifolia (Vent.) Weiss = A. millefolium L. vat. asplenifolia (Vent) Fioiri = A. millefolium L. var. crustata Rochel = A. inundata Kondrat.' So one of the synonyms of Achillea asplenifolia Vent. (which is listed in the Flora Europaea under No. 27) is Achillea inundata Kondrat. But according to the Flora Europaea, A. inundata is either a relation of A. millefolium subsp. millefolium (see above) or of A. pannonica. If it belongs to subsp. millefolium it should have 2n=54, or if it belongs to A. pannonica 2n=72, but if it is a synonym for A. asplenifolia it will have only 18 chromosomes (2n=18). It is obvious that there is a little confusion here!

The Chemist

The second human factor with a bearing on this problem is the work of the analytical chemist, the pharmaceutical chemist, the pharmacologist, etc. A survey of the literature shows quite clearly that the botanist and the chemist are two totally distinct manifestations of the human race, living in different worlds.

Out of 25 research papers, drawn from all over the world, on the chemical analysis of Achillea plants, 15 did not mention which Achillea specimen was involved. They simply stated 'belonging to the Achillea complex', 'A. millefolium complex', or just 'yarrow'. No plant specimens were deposited. Even given the outstanding analytical work done to determine the constituents, the failure to supply specimens reflects a lack of scientific rigour; in some cases it renders the work completely useless, and even increases the existing confusion.


Does all this matter? Perhaps not, if one is interested only in the academic aspects of taxonomy and chemical analysis. But for the phytotherapist these distinctions are crucial. Until recently herbal practitioners, who were and are chiefly interested in the action(s) and medicinal uses of a plant, were often unaware of the importance of knowing its exact botanical name or the chemistry and pharmacology of its active constituents. This situation is changing as phytotherapists come to realize that the traditional actions of a plant are due to the presence of certain constituents, which in turn depends on the type, species, or variety being used.



To treat somebody with yarrow for an inflammatory disorder when the plant has not a trace of chamazulene, or for amenorrhoea when there is little or no thujone present, may lead to therapeutic failures, undermining patients' confidence in phytotherapy.

The irony of the situation we now find ourselves at the end of the twentieth century is that phytotherapy is expected to apply GMP and quality control -- its products neatly analysed and standardized -- while we don't even know which species we are dealing with! Of course, in former times, when the herbalist either grew his own herbs or collected them locally from the wild, he could count on always being able to obtain the same plant, or species of plant, and therefore knew, as a result of many years' experience, what that particular plant did for his patients. In the modern world, however, most phytotherapists buy their herbs, directly or indirectly, from a wholesaler. If wholesalers are asked what kind of yarrow they supply, the reply is generally 'A. millefolium', and further enquiries about Achillea's different species, subspecies, etc., will usually elicit the response that all the material sent from different parts of the world is the same and is 'just yarrow'. Suppliers can hardly be blamed for this, as no one has ever questioned this basic assumption. Of all the articles on yarrow, only one review article on millefolium -- by Chandler et al. in 1982 -- has been published [ 4]. This gave a very thorough overview of what had been published about Achillea in the previous 20 to 30 years, acknowledged the general confusion, but offered no solution to it. Earlier, Wolfgang Spaich [ 5] reviewed Achillea in his book Moderne Phytotherapie (1977), and cited numerous German authors, none of whom mention the problem under discussion. Again, recent textbooks like Weiss's Herbal Medicine [ 6] or Wichtl's Teedrogen [ 7] simply mention Achillea millefolium as such, without the slightest hint that there may be other species. Even the most up-to-date German textbooks, such as Steinegger and Hänsel's Lehrbuch der Pharmakognosie und Phytopharmazie [ 8], say nothing about different species, subspecies or varieties. Tables 1-3 and Box 1 give an overview of the existing sp ecies, subspecies and medicinal varieties of Achillea.




How is one to resolve the confusion surrounding Achillea? The best solution from the phytotherapist's point of view would be to have a guaranteed supply of pure Achillea millefolium subsp. millefolium (2n=54) and of a species containing chamazulene such as Achillea collina (2n=36). Ideally, a comprehensive collection of all the different species should be established in order to study morphology and chemical analysis -- though this again is fraught with difficulty, as many species adapt themselves to new surroundings, in the process changing not only their morphology but their constituents as well. The following example illustrates this point [ 9]. Research workers from the Faculty of Science in Lisbon, Portugal, were working on the composition of a volatile oil obtained from Achillea millefolium subsp. millefolium which was growing in the Lisbon Botanical Garden. However, they found that the oil of other plants obtained from the species in Lisbon but grown in the north of Portugal was substantially different from the oil obtained from the Lisbon plants.

Given the occurrence of such chemotypes, another possibility is to have several collections in different habitats, specific for lowland, mountainous and alpine species and species favouring a dry or wet habitat. These then could be identified, the chromosome number established, and the chemical make-up analysed.


It is hoped that, by bringing the problem to public attention, this article will prompt a greater research effort towards resolving it. Such an effort is all the more urgent in that yarrow is a very important herb for phytotherapists. Its medicinal virtues cannot be better illustrated than by the following anecdote from Coffin's A Botanic Guide to Health (1859) [ 10]:

An itinerant speaker, of the Society of Friends, who professed some knowledge of medicine, was asked what would cure a cold. He answered, 'Take a pint of yarrowtea made strong on going to bed and put a hot brick on thy feet, wrapped in a wet cloth with vinegar and thou wilt surely be well in the morning.' This, to the inquirer, seemed very rational, for he knew from experience that sweating was good for a cold. Not satisfied, he next asked the old gentleman what he would recommend for rheumatism. The answer was, 'Take a pint of yarrow-tea made hot on going to bed, with a hot brick at thy feet as before and thou wilt soon be well.' Being asked what would expel worms from children, he answered as before, 'Give them a strong tea of yarrow and put a warm brick to the feet and they will be cured speedily.' Our brother's patience was fairly taxed by being asked remedies for every disease that could be brought to mind; the answer invariably was, 'A strong tea of yarrow, with a hot brick wrapped in a cloth wet with vinegar applied to the feet and health would soon be restored.'

Comical as the old Friend's advice may appear to many, we have since proved the correctness of most of his sayings and are of the opinion that, if yarrow was the only medicine sold at the drug shops there would not be one quarter of the disease that there is at the present time.

Many modern authors might agree. According to Spaich [ 5], 'It is nearly impossible to bring all the therapeutic uses of Achillea millefolium under one common denominator.' And indeed, the present-day phytotherapist knows from experience the wide field of application of this herb and, consequently, the importance of clearing up the existing confusion. A note for the practising phytotherapist: the yarrow we are generally using in the United Kingdom, Ireland, the Netherlands, Belgium, Germany and Denmark is probably Achillea millefolium subsp. millefolium (2n=54). As long as it is locally collected -- for no one can be sure of the species of imported material -- it is just yarrow.

(1.) Carnat, A.P.; Lamaison, J.L. Achillea millefolium L. subsp. alpestris (Wimm. and Grab.) Gremli, source de chamazulene. Plantes médicinales et phytothérapie, 24(4): 238-41 (1990).

(2.) Hansel, R.; Keller, K.; Rimpler, H.; Schneider, G. Achillea. Hagers Handbuch der pharmazeutischen Praxis, Vol. 4, pp. 45-54.1992.

(3.) Kastner, U., et al. New Proazulenes of Different Taxa Belonging to the Achillea millefolium Group. Planta medica, 57 (Suppl. 2) (1991).

(4.) Chandler, R.F.; Hooper, S.N.; Harvery, M.J. Ethnobotany and Phytochemistry of Yarrow, Achillea millefolium, Compositae. Econ. Botany, 36:203-23 (1982).

(5.) Spaich, W. Achillea millefolium. Moderne Phytotherapie. Haug Verlag, Heidelberg, 1977.

(6.) Weiss, R.F. Herbal Medicine, pp. 92, 315. Beaconsfield Publications, Beaconsfield, 1988.

(7.) Wichtl, M. Teedrogen, pp. 430-32. Wissenschaftliche Verlagsgesellschaft, Stuttgart, 1989.

(8.) Steinegger, E.; Hansel, R. Lehrbuch der Pharmakognosie und Phytopharmazie. 4th edn, pp. 317-79. Springer Verlag, Heidelberg, 1988.

(9.) Fiqueiredo, A.C.; Barroso, J.G.; Pais, M.S.S. Composition of the Essential Oils from Two Populations of Achillea millefolium L. spp. millefolium. Journal of Chromatographic Science, 30:392-95 (1992).

(10.) Coffin, A.I. A Botanic Guide to Health, pp. 88-89. London, 1859.

The British Journal of Phytotherapy.


By Hein Zeylstra

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