As ornamentals, yarrows offer everything from 2-inch, mat-forming evergreen ground covers to 4- to 5-foot-tall flowering specimens for the perennial border. In considering the various species, I like to classify them according to their native habitat and growth habit. Those of alpine origin are generally low growing (flowering height about 10 inches), whereas those native to lower elevations are more vigorous and invasive and from 2 to 5 feet tall in flower.
Alpine yarrows. Many of the alpine yarrows are excellent candidates for a rock garden, for low edging to a border, or for a small-scale, dramatic ground cover, especially among stepping stones. All cherish sun and well-drained soil, and all are long-lived and tolerant of severe cold. Although wet winters can be detrimental to the silver-foliaged species, the damage can be minimized by planting them so that their foliage spills over rocks or gravel and thus dries quickly when it does get wet. Most of the alpines bloom in late spring and early summer, but some will continue well into late summer. If prevented from flowering, they are a good choice for miniature landscapes or model railroad gardens. Several of the alpine species are used in their native countries to impart a bitter, aromatic flavor to herbal liqueurs, which is said to make the drink more intoxicating.
• Silvery Yarrow (A. umbellata, usually offered as A. argentea)
The delightful evergreen silver filigree foliage of silvery yarrow forms a small mound or cushion topped by pretty little pure white daisies on 6-inch stems, which keep well in a fresh bouquet. Native to southern Greece, it prefers alkaline soils and is hardy to Zone 4.
• A. x jaborneggii
This hybrid (its parents are A. clavennae and A. erba-rotta subsp. moschata) is much like silvery yarrow, but the foliage is a little greener in spring. It, too, forms a dense evergreen mat with fine white flowers.
• A. x lewisii ‘King Edward’ (sometimes offered as ‘King Edward IV’, VII, or VIII!)
This attractive cross between A. clavennae and A. clypeolata forms a prostrate carpet of woolly gray-green foliage with lemon yellow flowers from June to August.
• Woolly Yarrow (A. tomentosa)
Woolly yarrow’s bright golden yellow flowers on 4- to 6-inch stems contrast strikingly with its finely cut, woolly silver foliage; when bruised, the leaves are delightfully aromatic. It blooms from late May through the summer and needs a lean, dry soil with perfect drainage. A gravel mulch will enable the foliage to dry rapidly where winters are wet. The woolly foliage is a magnet for disease in hot, humid areas. This species is native to temperate Europe. ‘Aurea’ (perhaps synonymous with ‘Maynard’s Gold’) has deep golden flowers and spreads rapidly; ‘Moonlight’ is a mat-former with foliage only 1 to 2 inches tall but with foot-long flower spikes of pale yellow flowers in June and July.
Yarrows of lowlands. When I first began growing herbs twenty years ago, yarrow flowers came in dirty white, pinkish red, or mustard yellow. Since then, thanks to intensive breeding programs, especially in Germany and England, the color range of this group of yarrows has been expanded to include pastels, warm muted shades, and dark tones. The new hybrids are also shorter, more compact plants that are useful in the perennial border.
• Common Yarrow (A. millefolium)
Common yarrow is native to temperate Europe, western Asia, and North America; the Old World form has also naturalized in North America along roadsides, in vacant lots, and perhaps in your own backyard. Flowers are usually gray to white but may be pinkish at higher elevations.
Today’s yarrows are receiving well-deserved appreciation for their ornamental value.
Besides offering an exciting range of flower colors, the improved cultivars are generally less invasive than the species. (Don’t let them go to seed, though, or they may revert to the species!) I’ve found that after working among plants of common yarrow or its cultivars for a while, my wrists begin to itch and break out in a mild rash (but it’s a handy excuse to get out of weeding the yarrows).
• Fern-leaf yarrow (A. filipendulina)
This species, native to the Caucasus and Asia Minor, is a handsome plant that forms a large clump of deeply cut, feathery, soft green foliage. It grows up to 5 feet tall with strong, leafy flowering stems and large, lemon yellow flower heads that are excellent either fresh cut or dried. (Fresh flowers will last longer if the lower leaves are stripped off.) You may need to stake plants or remove some of the flower heads when in bud to keep the stems from flopping from the sheer weight of the flower heads. They do best in full sun and cool climates. Because the center of the clump tends to die out after a few years, I divide plants at least every three to four years, saving the more vigorous outer sections and discarding the middle. The cultivars offer more flowers and stronger stems than the species. ‘Gold Plate’ (sometimes called ‘Big Head’) has golden yellow flowers and the largest flower head of all the yarrows–it’s 6 inches in diameter. ‘Parker’s Variety’ has slightly smaller yellow flowers on 3- to 4-foot stalks.
• Maudlin, Sweet Milfoil, Sweet Nancy (A. ageratum)
Native to Italy and Spain, this attractive yarrow was introduced into En-gland in 1570. The leaves are aromatic and sweet smelling but have a distinctly bitter taste. The yellow tansylike flowers are borne in dense, rounded clusters on 18-inch stems; they were once used to flavor ales and as an ingredient of “sweete washing water”.
• English Mace, Garden Mace (A. decolorans)
This species is one of the few yarrows known for its culinary use. The narrow, sharply toothed green leaves have a distinctive nutmeg or mace scent; small quantities of the finely minced leaves add a unique piquancy to potato salads, soups, stews, and cheese dishes. Like
A. ageratum, this species is a hybrid of A. ptarmica. It was introduced into En-gland from Switzerland in 1798. It spreads slowly and sends up 18- to 24-inch stalks bearing loose clusters of white or cream-colored flowers with a darker center. The flowers were once used to treat stomach disorders. ‘W. B. Childs’ is an excellent noninvasive cultivar that likes a moisture-retentive soil in either sun or partial shade.
(Although The New Royal Horticultural Society Dictionary of Gardening considers A. ageratum and A. decolorans synonymous, plants with these names that I’ve purchased are distinctly different. I have retained the old species names here because that is how they are listed by mail-order nurseries in the United States.)
• Sneezewort (A. ptarmica)
The green leaves of this species are long and linear, unlike those of most other yarrows. In the wild, it thrives in moist, even boggy soils. The leaves were once used to add bite to salads. In cultivation at least since 1542, this herb when dried and powdered was taken like snuff “to cleanse the head of rough slimy humours,” according to the En-glish herbalist Culpeper. The rhizomes were a remedy for fatigue and urinary disorders. The loose clusters of white ray flowers with central disks of dingy white, in bloom from July to September, were infused in bathwater for their relaxing effect.
Double-flowered forms have been known since the sixteenth century; today, double forms are grown almost exclusively because their pure white flowers on stout stems are particularly appealing as filler in flower arrangements. (All of the double-flowered cultivars produce a few single flowers as well.) All are vigorous spreaders, tolerating a wide variety of soil conditions. To keep them looking their best, grow them lean and mean–save the fertilizer for other herbs.
‘Angel’s Breath’ is 18 inches high with many small, buttonlike white flowers on a compact plant. ‘The Pearl’ (also called ‘Schneeball’ or ‘Boule de Neige’) is the oldest and best-known double-flowered form, with neat white buttons on 2-foot branching stems. ‘The Pearl Superior’ is a related cultivar which is said to flower from seed in as little as three months. ‘Perry’s White’ is perhaps whiter than the preceding cultivars, and its stalks are longer (up to 30 inches) but less rigid. Its rays are a bit more rounded than those of ‘The Pearl’, and the flowers open slightly earlier.
• Some Outstanding Hybrids
Yarrows both in the wild and in the garden hybridize freely. Many of today’s garden yarrows have their origins in these crosses, whether intentional or otherwise. A. ‘Coronation Gold’, one of the finest large yellow-flowered yarrows, was a chance cross found in an English garden in 1952. It was one of the first yarrows that I planted in my herb garden because it does well in cool summers and doesn’t “run” as much as common yarrow and its cultivars do. With its huge, soft gray-green leaves, it is one of the best yarrows for winter foliage color and beauty. This yarrow is shorter than A. filipendulina and has better branching flower stems that require no staking.
The Galaxy Hybrids, developed by German plant breeders, offer a wide range of flower colors, including rich crimson, pinks, peach, and tawny yellow. Although their foliage is similar to that of common yarrow, the flower heads are much larger and their stems much sturdier. The flower colors do tend to fade rapidly in hot weather, but the combination of both fresh and faded flowers on the same plant simultaneously is very attractive.
A. ‘Moonshine,’ a cross from Alan Bloom of Bressingham Gardens in En-gland, is a beautiful silver-foliaged, long-blooming compact plant–probably the finest silver-foliaged yarrow yet. The flat flower heads are a bright sulfur yellow that dry to a gray-yellow. I grow this cultivar near a purple sage, and the color and foliage contrast are spectacular. If I had to choose just one of the yellow-flowered yarrows, it would be this one. It needs dividing every two to three years and must have excellent drainage. Unfortunately, where summers are hot and humid, ‘Moonshine’ often simply “melts” away.
Today’s yarrows are receiving well-deserved appreciation for their ornamental value. I use the taller-growing species to provide a natural and colorful vertical balance in the garden. The large flower heads seem to add a mid-border “cap” to the design, while the gray-green or silver foliage unifies diverse color schemes. There’s something simple and straightforward about yarrows that reminds me that for all our new modern-day gardens and fancy cultivars, we are not far from the field or mountainside where they all first originated.
Andy Van Hevelingen and his family grow herbs in Newberg, Oregon. He is a frequent contributor to The Herb Companion.