Achillea, yarrows |
Single flower head of Achillea ptarmica - the sneezewort
Flower heads of Achillea
millefolium, the common yarrow,
usually they
are white.
Achillea filipendulina, the fernleaf yarrow, blooms yellow, as here, the cultivar 'Credo'
The
willowleaf yarrow (Achillea
salicifolia)
occurs
only in the eastern part of Germany
100 to 200 species exist in this genus, depending on the classification, and can be found in sub-tropical, temperate and arctic areas in North America, northern Europe and northern Asia.
These are usually pleasantly scented herbs and subshrubs, often with a rhizome (rootstock). They usually form erect, robust stems, which may be branched. The basal leaves often wither before flowering, the stem leaves are alternate and like the basal leaves often frequently pinnatifid, rarely simple. The lamina is linear to linear-lanceolate.
The flowers are arranged in small heads with 3 to about 12 mostly female ray florets and 0 (rarely) to over 75 hermaphrodite disc florets. The ligules are roundish, usually white, but sometimes yellowish, reddish or purple. The disc florets are whitish, gray, reddish or yellowish. The fruits (achenes) are elongated and flat, often with 2 lateral ribs.
The flower heads are surrounded by a hemispherical or bell-shaped involucre. The phyllaries are arranged in 1–4 rows. The flat or slightly curved receptacle shows respectively one palea per disc floret. The paleae are membranous and slightly to strongly folded up.
Floral formula: |
↓ K0 C(5) G(2) inferior
and * K0 [C(5) A5(connate)] G(2) inferior |
The flower heads are arranged in seemingly umbellarly inflorescences, so they are sometimes mistaken for Apiaceae. If one look closely at the inflorescence, one realizes that it is a panicle (irregular branches). One speaks therefore of a umbel-like panicle (corymb).
Yarrows as host and food plants
Yarrows are food plants of various insects. Stictopleurus punctatonervosus sucks mainly saps of different Achillea species. The caterpillars of Dewick’s plusia (Macdunnoughia confusa), a small moth, feed on yarrow and nettle. Caterpillars of the genus Gillmeria need as food plants yarrow or tansies.
But not only animals, even a plant feeds on the yarrow. The rare yarrow broomrape (Orobanche purpurea) is a root parasite. It extracts its host plant water and nutrient salts because itself forms no chlorophyll.
Historical publications
According to tradition by Pliny the Elder (approx. 23–79. AD.) the Greek hero Achilles healed King Telephus, who was wounded in the Trojan War, with a plant (herb of Achilles).
Pedanios Dioskurides (1st century AD.) described Achilleios as a plant with spindle-shaped branches that was a span tall or longer. At these would grow delicate leaves, which often had oblique cuts, similar to the coriander. They were slightly bitter and sticky and possessed a strong, pleasant, medical scent.
The inflorescence was round and the flowers white, dark red, or yellow. Achilleios would only grow on good soil. Its inflorescence would, if minced, stop bleeding and inhibit inflammation. A tea would help against diarrhea and as a sitz bath against discharge in women.
Meaning of the species names
- millefolium: lat. millefolius = thousand-leaved (refers to the finely divided leaves)
- ptarmica: gr. ptarmos = sneezing (refers either to the spiciness of the roots or on the leaves, which should trigger sneezing if plugged into the nose)
Interesting notes
- For the Chinese oracle "I Ching" were used 50 rods, made of robust stems of the Siberian yarrow (Achillea sibirica), which had grown at sacred locations.
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There are several cultivated varieties of yarrow for example with yellow, red or double flowers. The garden plants can cross with wild species, which makes the determination, that often is already very difficult, especially at the common yarrows, not any easier.
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Like the ground-ivy (Glechoma hederacea) yarrow has been used before hops for flavoring and preserving beer.