Hardiness of Mace Yarrow

Mace Yarrow (Achillea decolorans) is listed as a tender perennial. How far north is it in fact winter hardy?

We do not have a hardiness zone rating for mace yarrow, but we believe it to be hardy in zones 7-9. It has not been grown long enough across North America yet for a reliable zone rating. L.H. Bailey's "Standard Cyclopedia of Horticulture" (1922) says that it is a native of Europe. It is not mentioned in L.H. Bailey's "Hortus Third" (1976), which suggests that the plant was not commonly cultivated.
One of the few books to mention this plant is Dorothy Hewer's "Practical Herb Growing" published in London by G. Bell and Sons in 1941 (revised by Kay Sanecki in 1969). Here is what she says about mace yarrow:
"This little plant, growing to about 1-1/2 ft. [45 cm] in height, with white flowers rather like those of yarrow, has very aromatic, dark green, toothed leaves. It is not the 'mace' of commerce, which consists of the aril of the fruit of a myristicaceous nut, but the aromatic leaves are used to flavour soups and salads. It is propagated by division."
We think this plant deserves greater popularity. It is easy to grow, is highly aromatic and it invites creative use in the kitchen.