Several factors can make a flower rare. In some cases, the rare flower only grows in a limited area. In other cases, the flowers are rare because the seeds are not hardy and only a small percentage will actually germinate. Rare flowers can be found and grown in the home garden in limited areas of the United States.
Lion's ear (Leonotus leonurus) is also known as wild dagga or lion's tail, and is a member of the mint family. The plant grows up to 6 feet tall with a spread of from 2 to 3 feet with lance-shaped leaves that grow from 2 to 4 inches long. The 2-inch long, orange-red flowers are tube-shaped, bloom from summer through the early part of the winter and grow in 4-inch wide clusters. The plant is a native of South Africa and likes full sun and a dry soil. Lion's ear is hardy in USDA Zones 9 through 11 and is a favorite of butterflies and hummingbirds.
Purple heart (Tradescantia pallida) is also known as purple queen or purple-heart tradescantia, and is a member of the spiderwort family. The plant is a ground cover with leaves that are a deep purple on top and violet-pink on the bottom, growing to be about 3 to 5 inches long and 1 inch wide. The pale orchid-pink flowers are less than 1 inch wide and bloom in warm weather, but only open in the morning. The plant is native to eastern Mexico and likes full sun and a rich, sandy soil. Purple heart is hardy in USDA Zones 8 to 11 and is a good choice for a rock garden.
Parrotlily (Alstroemeria psittacina) is also known as parrot flower, red parrot beak, New Zealand Christmas bell, Inca lily and Peruvian lily, and is a member of the amaryllis family. The plant grows up to 30 inches tall with pale-green leaves clustered at the tips of the stems. Clusters of red, yellow-green edged, 1 to 2-inch long flowers appear in the early summer. The entire plant will become straw colored before it goes dormant for the winter. Parrotlilies like full sun in the milder climates and partial shade in the hottest climates, as well as a moist and well-drained soil. The plant is hardy in USDA Zones 7 through 10.