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By Todd Boland (Todd_Boland)
(Editor's Note: This article was originally published on December 26, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.) It is not very often that a common roadside weed becomes a garden ornamental, but the lowly yarrow is one shining example. The common yarrow, Achillea millefolium, is native throughout the northern hemisphere. While yarrow is native to North America, it is the European subspecies that is the common weed also roadsides, waste places and unfortunately, our lawns. The wild form, with its rather dull white flowers, is hardly ornamental. However, the first inklings that this species could have ornamental potential arose from naturally occurring pink forms. Plant breeders started breeding pink forms to pink forms and lo and behold, darker pink shades arose. So not surprisingly, the first ornamental cultivars were various pink to cherise shades.
The natural wild forms of common yarrow Achillea millefolium is not the only yarrow species; in fact there are about 65 species within the genus. Most have no garden value but there are a few exceptions. Appearing similar to the common yarrow are A. filipendulina and A. clypeolata. These two Eurasian species have more silvery hairs than the common yarrow, but more importantly, have bright yellow flowers. They also do not appear to be as invasive. There are several named selections from these two species and their hybrid offspring including A. taygetea, ‘Moonshine', 'Coronation Gold', 'Cloth of Gold' and 'Anthea'.
Examples of yellow-flowered yarrow include 'Moonshine' (top left), ''Anthea' (top right), 'Coronation Gold' (lower left) and 'Cloth of Gold' (lower right) Plant breeders, who are always pushing the bounds of genetic mixing, managed to cross these yellow cultivars to the pink and white common yarrow, and a star was born! From these breeding experiments arose the multitude of modern-day yarrow cultivars; 'Summer Pastels', 'Paprika', 'Cerise Queen', 'Terracotta', 'Apricot Delight'...and the list goes on. There are now well over 30 named cultivars of yarrow, which extend the colour range from white, pink, red, orange, yellow and innumerable shades in between. About the only colours not found are shades of violet and blue. Most of the modern hybrids have also lost their invasive tendencies, not to say they are not vigorous plants for indeed they are!
Examples of modern-day yarrow include 'Terracotta' (upper left), 'Orange Queen' (upper middle), 'Red Velvet' (upper right), 'Strawberry Seduction' (lower left) and 'Summer Pastels' (lower right) At this point I should also introduce three other reasonably popular Achillea species; A. tomentosa, A. clavennae and A. ptarmica. The previous two species are often called the dwarf yarrows. Both forms low mats of finely-divided, silvery-silky leaves with upright flower stems 20 to 40 cm in height. Achillea tomentosa has yellow flowers while A. clavennae has large white flowers. Both are ideal subjects for the front of the border or the rockery. Achillea ptarmica is often called sneezewort. This plant looks quite different from the typical yarrow. It has narrow, smooth leaves and large individual flowers compared to typical yarrow. The most popular cultivar is 'The Pearl' with double white flowers on stems upwards to 150 cm. This species can run by underground stolons so do not plant it next to shy neighbors.
Other Achillea species include A. clavennae, A. ptarmica 'The Pearl' and A. tomentosa Culture is easy for yarrow. They simply need full sun and well-drained soil. They seem to thrive in alkaline or acidic soil and certainly do not require rich, fertile soil (thanks to their weedy past). They are very drought- and salt-tolerant so are suitable for xeric gardens as well as seaside gardens. They are bothered by few pests and diseases. Hardiness is not a problem as they can easily survive zone 3 and even into zone 2. The blooming season lasts for weeks and their flowers may be hung and dried for use in dried-flower arrangements. Some selection have very silvery-foliage which lends them interest throughout the entire growing season. Overall, they are tough plants. We just have to get past their weedy heritage. Yarrow, you've come a long way, baby! I have many people to thank for the use of their pictures: bootandall ('Terracota'), Calif_Sue ('Red Velvet'), Gindee77 ('Moonshine'), Happenstance ('Coronation Gold', 'Orange Queen'), jg48650 ('Pretty Belinda', A. tomentosa), kimmy222 ('Strawberry Seduction'), kniphofia (A. ptarmica 'The Pearl'), poppysue ('Anthea') and saya ('Cloth of Gold' and 'Summer Pastels').
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