Although wild forms of yarrow that exhibit unusual qualities (red flowers instead of white, for instance) have been collected in European gardens for at least 600 years, serious efforts to breed new and improved strains only started in the early 1900s. The first breakthrough came with A. x lewisii ‘King Edward', which arrived just in time for Edward VII's coronation in 1902. Still going strong and very popular with rock garden enthusiasts, this Zone 4 variety bears pale yellow flowers on short (20-cm) stems with a spread of 20 to 30 centimetres. It performs best in full sun.
Oddly enough, the next significant yarrow cultivar also has royal associations: A. ‘Coronation Gold' was introduced in 1952 and named in honour of Queen Elizabeth II's accession to the throne. A statuesque plant (90 cm tall by 40 to 50 cm wide), it's crowned with golden yellow flower heads and is often seen partnered with stately purple Salvia nemorosa ‘Lubecca' or S. n. ‘Ostfriesland' a.k.a. ‘East Friesland'.
In the meantime, various cultivars of A. millefolium were being developed, the most famous of which, A. m. ‘Cerise Queen' (introduced by the English rose-breeding firm Harkness), is still widely encountered in gardens and nurseries alike. With the success of ‘Cerise Queen', breeders were anxious to expand the colour palette of the genus beyond white, yellow and red, and the first horticulturist to do so was Wilhelm Kikillus of Germany. In 1986, he launched his Galaxy Hybrids with just four cultivars: the light pink A. ‘Apfelblüte' (a.k.a. ‘Appleblossom'), the cream-coloured A. ‘Hoffnung' (a.k.a. ‘Great Expectations'), the bright red A. ‘Fanal' (a.k.a. ‘The Beacon')—which sports yellow centres—and my personal favourite, A. ‘Lachsschönheit' (a.k.a. ‘Salmon Beauty').
Those four were so successful (all are still available) that others have been added over the years, including A. ‘Wesersandstein' (a.k.a. ‘Wexer River Sandstone'), which is pinkish red, fading to sandy cream, and A. ‘Summerwine', which is dark red. The more recent introductions are slightly shorter (60 by 40 to 50 cm) than their feisty forebears, which are between 75 and 90 centimetres tall with a spread of 45 to 60 centimetres, as breeders responded to consumer demand for sturdier, more compact plants with less tendency to flop.
Other worthy hybrids of A. millefolium include ‘Fire King' (rich red, 60 cm), ‘Lilac Beauty' (lavender, 75 cm), ‘Paprika' (orange-red, 60 to 75 cm) and ‘Terracotta' (rusty orange, 75 to 90 cm). All have a spread of 45 to 60 centimetres.
Lovers of gold tones won't want to overlook the August-flowering A. filipendulina (1.2 m by 45 cm), or its excellent cultivars ‘Altgold' a.k.a. ‘Old Gold' (60 by 45 cm), ‘Cloth of Gold' (1.5 m by 60 cm) and ‘Gold Plate' (1.2 m by 65 cm).
Out of this world
With the advent of the Galaxy Hybrids, other breeders were quick to jump on the yarrow bandwagon, which has resulted in three additional series, all hardy to Zone 3.
Achillea ‘Summer Pastels' Heat and drought tolerant with fade-resistant flowers in shades of lavender, purple, apricot, cream and rose. 260 cm, 1 50 cm
A. ‘Colorado' Bred for heat tolerance and a compact habit in complementary hues of pink, red, yellow, white and apricot. 21 45 to 60 cm
A. millefolium ‘Debutante' Large ivory, rose, salmon, lilac or purple flower heads (to 15 cm across) on short, sturdy plants. These are guaranteed to repeat flower without deadheading or cutting stems down to crown after their first flush of bloom. 245, 1 60 cm.