Herb Profile: Yarrow Varieties

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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.