Gentians are tropical garden plants that in cooler climates are popular houseplants or garden annuals. There are many varieties of gentians; one of the most common is the Persian violet (Exacum affine), also known as the German violet. It has violet blue petals and a yellow center. It grows only to a height of about 6 to 12 inches tall and makes an excellent groundcover, if desired. Purchase and grow gentian Persian violets from seed or as small plants.
Decide how many plants or seeds to purchase. Gentian Persian violets are spaced 6 to 12 inches apart so buy enough plants accordingly. For seeds, buy at least three to five seeds for every plant you want to grow because not all seeds will grow well.
Buy gentian Persian violet small plants in the spring or summer when nurseries usually have them in stock. Local nurseries may have them, but most likely you'll have to purchase them online or through a catalog, and can do so year-round. Look for plants that appear healthy and disease- and pest-free.
Know that seeds sown in the winter bloom in the summer and seeds sown in the fall bloom in the spring if you are going to transplant them outdoors. For outdoor seed planting, in USDA plant hardiness zones nine and cooler, plant seeds in the spring or early summer when temperatures consistently reach 70 F. In warmer zones, you can also sow gentian Persian violet seeds in the fall.