Buy seedlings in very early spring. Annual dianthus comes in a range of colors from red to white to pink to lavender with various markings on the flowers.
Plant seeds, if that's your choice, indoors about 8 weeks before your region's last average frost date.
Plant seedlings outdoors in full sun to very light shade with good drainage; dianthus does best in places like rock gardens, slopes and raised beds. Plant in very early spring since dianthus does best during cool weather and fades or dies out altogether once temperatures top 80.
Work a spadeful or two of sand into the soil to a depth of at least 18 inches if drainage isn't excellent.
Trim off spent blooms to promote longer flowering.
Pull out plants in fall after frost kills them.