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Brief Summary

    Achillea ptarmica: Brief Summary
    provided by wikipedia

    Achillea ptarmica, the sneezewort, sneezeweed, bastard pellitory, European pellitory, fair-maid-of-France, goose tongue, sneezewort yarrow, wild pellitory, or white tansy, is a European species of herbaceous perennial flowering plant in the genus Achillea. It is widespread across most of Europe and naturalized in scattered places in North America.

    Achillea ptarmica has loose clusters of showy white, flower heads that bloom from June to August. Its dark green leaves have finely toothed margins. Like many other plants, the sneezewort's pattern of development displays the Fibonacci sequence.

    The name ptarmica comes from the Greek word ptairo (=sneeze) and means 'causes sneezing'.

Comprehensive Description

Morphology

    Comments
    provided by eFloras
    Achillea ptarmica is naturalized from Eurasia. "Double-flowered" plants originated as cultivars; apparently, they persist outside of cultivation.
    Description
    provided by eFloras
    Perennials, 30–60+ cm (rhizomatous). Stems 1, erect, branched distally, proximally glabrate, distally villous or tomentose. Leaves sessile; blades linear to narrowly lanceolate, 3–10 × 3–5 mm, (bases slightly clasping, margins usually serrulate, rarely subentire), faces glabrous or sparsely hairy on midveins adaxially. Heads 3–15+, in simple or compound, corymbiform arrays. Phyllaries 25–30+ in ± 3 series, (light green, midribs yellowish, margins light brown) lanceolate to oblanceolate, faces tomentose. Receptacles flat to slightly convex; paleae oblanceolate, 3–4 mm. Ray florets 8–10(–13), styliferous and sterile (45–70, pistillate, fertile, in horticultural doubles); corollas white, laminae suborbiculate, 4–5 × 4–5 mm (5–7 × 3.5–4.5 mm in doubles). Disc florets 45–75+ (sometimes 0 in doubles); corollas grayish white, ca. 3 mm. Cypselae 1.5–2 mm. 2n = 18.