This is a combination of plants we ended up with purely by accident, a clump of Asclepias tuberosa and an unknown white variety of  Achillea millefolium.   We started with a couple plants of each growing side by side.  They are both hardy plants that spread quickly.  After just a couple of years, we now have a large clump of both plants that mixed in together.  They flower at the same time and the bright orange flowers of the Asclepias complement the flattened white flower heads of the Achillea.

Both of these plants are excellent perennials for attracting butterflies.  Achillea, commonly called yarrow, is one of the most visited flowers in our garden.  Asclepias tuberosa, also known as butterfly weed, belongs to the milkweed family.  Milkweed leaves are the sole food source for the caterpillars of the monarch butterfly.  The milkweed flowers are frequently visited by many types of butterflies and we often find the foliage full of monarch butterfly caterpillars.