Black Beauty and Iowa each produce deep purple flowers. Both the vibrant colors and the nectar supply of the heliotrope are excellent attractants for the butterfly. There are over 600 species of true asters, offering the butterfly gardener an almost unlimited choice of which ones to plant. Asters vary greatly both in color and shape, ranging from alpine varieties only six inches high to open branching plants of six feet. The tall species are ideal for back borders, whereas the compact varieties make very showy front borders for flower beds.
Asters also thrive in all planting zones.
Their flowers are either white or shades of red, pink, lavender, purple or blue, with most having yellow centers. Asters are resistant to most insects and plant diseases. This is a real plus, since the use of chemical pesticides is not appropriate for butterfly gardening. This unique flower attracts both caterpillars and butterflies. There are about 250 species of penstemon, with most being native to the western part of the United States from Canada to Mexico.