This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Perennials with alternate simple or compound leaves. Flower-heads small, corymbose; involucral bracts oblong, often brown and scarious. Receptacle paleaceous. Ray-florets few, sometimes relatively large and showy. Pappus none. The species are estimated at fifty, dispersed over Europe, temperate Asia, and North America. The name is of classical origin.
Fig. 138. Achillea filipendulina. (1/4 nat. size.)
1. A. Millefolium. Yarrow. - The pink- or purple-flowered varieties of this common weed are equally effective with any of the other species and of long duration. The leaves are tri-pinnately divided into numerous linear segments and the flowers usually white.
2. A. filipendulina (fig. 138). - This is very near the preceding but rather taller and having less finely-cut leaves, and pretty bright yellow flowers.
A. AEgyptiaca and A. tomentosa are dwarf tufted species with finely-cut cottony leaves and yellow flowers.
3. A. Ptdrmica. Sneezewort.- The only other native species. The leaves are simple and serrulate, the ray-florets larger, and the flower-heads larger and less numerous. There is a double white variety of this worthy of cultivation.
4. A. Glavennae. - A dwarf species belonging to the same group as the last. It grows about 6 inches, and is densely clothed with a white hoary tomentum. Leaves bipinnatifid. Segments broader than in the other species enumerated.