A very popular plant for dried flower arrangements is the silver dollar plant. Botanists classify the plant as Lunaria annua when it is an annual plant and as Lunaria biennis for biennial plants. Other common names are honesty or money plant, penny flower, and bolbonac. Many gardeners consider the silver dollar plant to be attractive most of the year. It has striking foliage, especially when variegated, and lovely flowers.
Technically, L. annua and Lunaria biennis belong to the Brassicaceae family. Native to Europe, the plant grows easily in many places where the temperatures are similar to the United States Department of Agriculture (USDA) hardiness chart's zones five through nine. Some gardeners in zones four and 10 or 11 have successfully grown the flower, though it often needs special care outside of its comfort zones. In the late 1500s to the early 1600s, famous herbalist John Gerard raised the silver dollar plant in his English garden at Holborn in central London.
The leaves of the silver dollar plant generally are ovate to heart shaped. They are coarsely toothed and light to mid-green. Usually the leaves grow to be about 6 inches (15 cm) long. Some varieties, such as 'Alba Variegata,' have variegated leaves. The leaves of 'Alba Variegata' and 'Variegata' are very similar. Whereas 'Alba Variegata' has white flowers, 'Variegata' has pretty purple or reddish purple flowers.
Most of the plants bloom in late spring. The blooms generally are cross-shaped and white to light purple in color. 'Munstead Purple' sports deep reddish purple flowers. Individual blossoms often are up to 0.5 inch (1.5 cm) across. Masses of these blossoms are borne in broad, leafy racemes that measure up to 7 inches (18 cm) long.
After the blooming period, the silver dollar plant sets on its flat seedpods that usually measure 1 to 3 inches (2.5 to 8 cm) across. They are round and brown. The treasured silver dollars are inside. The outer walls must fall off or be removed to reveal the silvery inner walls.
Many gardeners raise the silver dollar plant in a flowerbed or at the back of a border planting. The plant typically reaches heights of 36 inches (90 cm), with a spread of 12 inches (30 cm). In some climates, people raise it as a houseplant, greenhouse plant, or a container plant. If a grower raises it as a container plant, he may move it to the shade during the hottest parts of the day in tropical settings. In colder climates, she may move it to warmer areas in order for it to survive cold temperatures.