These perennial bring a palette of pastel tones to the summer garden.
Yarrow, or achillea is one of the most colourful perennials we can grow in summer borders. Right now these upright herbaceous perennials with their flat-topped flower heads are able to infuse plantings with a wide array of vibrant and pastel tones. What our native white and pale pink hued species Achillea millefolium might lack in this department the array of vibrant garden forms certainly makes up for in diversity of colour. Deep reds and crimsons, pinks, lilacs, yellows are expanded by a range of more subtle tones, including reddy-brown, biscuit, salmon and peachy tones. What makes them even more attractive is the central boss of flowers (disc florets) are in a different tone, often yellowish to the outer petals (ray florets). Flowers in some varieties attractively fade as they age, creating heads of blossom in multiple tones, and some gardeners keep the spent stems over winter for decoration. Those used for border plantings predominantly grow to around 60cm (2ft) or more tall, clothed in feathery aromatic foliage, spanning deep green, through grey-green to bright silver in some yellow flowered forms, making a lovely contrast.
Achillea prefer moisture retentive, but well-drained soil until they establish, when they become more drought tolerant. Although they will tolerate most soils as long as not constantly wet or droughted they grow best on neutral to chalky ones, than acid. Soil should also be not too rich or over fertilised as this will encourage them to overgrow and flop, also shortening their lifespan, which is around four years. They prefer full sun to do well and keep growth tight. They also need good air-flow to prevent mildew from forming, and so are not good in crowded leafy plantings. Shoots develop from a loose clump of basal buds, which are best lifted and divided every 2-3 years to keep them vigorous. Plants should be cut down to ground level in late winter when new shoots appear.