Yarrow (Achillea) is a hardy summer-blooming perennial for the sunny garden. There are many hybrids available and color choice is extensive, ranging from sulphur yellow to burgundy. Foliage texture and color vary as well. For these reasons, yarrow can be a versatile element in the landscape. Plant in well-drained soil and shear back the plant after flowering to rejuvenate foliage and encourage re-bloom. Yarrows are great for dried flower arrangements.
The white-flowering common yarrow (Achillea millefolium) is a perennial herb found in every region of the United States, according to the USDA/Natural Resources Conservation Service. It grows in meadows and along highways, and care should be taken not to grow it where it can crowd out other plants. According to the Missouri Botanic Garden, the second part of this yarrow's botanical name, millefolium, means thousand-leaved, which describes its fern-like foliage. The University of Illinois lists powdery mildew and botryttis as problems.
Common Yarrow Hybrids
The common yarrow hybrids share the same aromatic fern-like foliage as their parent, but are taller, more colorful and are better garden plants. They have the common yarrow's drought tolerance, spreading habit and can thrive in any well-drained soil, according to the Missouri Botanic Garden Colors range from reds to orange to pinks. If not cut back, they have a tendency to flop or "lodge," as the Missouri Botanic Garden describes the problem. Dividing every two to three years is recommended.
Other Yarrow Hybrids
Other yarrow hybrids, such as appleblossom and terracotta, share many of the traits associated with the common yarrow. The foliage is green, fern-like and has a strong aroma. Flopping occurs if left untended, especially for varieties that reach 3 feet tall, such as the hybrid yarrow fireland. The Missouri Botanic Garden also recommends dividing these varieties every two to three years. They will spread vigorously as well.
Fern-leaf yarrows (Achillea filipendulina) are yellow-flowered clumping forms. They range in height from the Achillea filipendulina gold coin dwarf at 15 inches to the gold plate at nearly 5 feet, according to the Missouri Botanic Garden. Staking is recommended for the taller varieties. The foliage is green or gray-green and aromatic. Achillea filipendulina alt gold is a true reblooming variety. These varieties also may get powdery mildew, advises the University of Illinois Extension.
Yellow-Flowered Varieties with Silver Foliage
Yarrows with silver foliage and yellow flowers offer great contrast in the garden. They are clumping varieties and therefore are somewhat tidier than the spreading forms. Achillea Coronation gold is an older variety. Achillea moonshine has a thicker and more silvery foliage. Achillea anthea' is a moonshine hybrid but with paler yellow flowers and is shorter, so may not need staking. According to the Missouri Botanic Garden, moonshine may suffer in the heat but anthea keeps fresh-looking foliage and flower color remains nice.
There is a rock-garden form of yarrow (Achillea tomentosa, aurea) with gray foliage and sulphur yellow flowers. According to the Missouri Botanic Garden the plant, grows to a foot at most and is called wooly yarrow
Stephanie Cohen yarrow (Achillea siberica) has pink flowers and a foliage texture and shape that is unlike other yarrows. The color is a dark glossy green and the leaves are needle-shaped.