Start carnation seeds indoors during the late winter, and you will be able to transplant your seedlings as soon as any frost danger has passed. Carnation seeds need only a few basics to survive, including pots, soil, water, and light. Once in the ground, your seedlings will continue to grow and will produce beautiful blossoms all summer long. Carnations require a minimal amount of care once planted and will bloom until the first frost.
Carnation seeds need to be planted in a shallow container. While commercial planting or seed trays will work for carnation plants, other options will work as well. Recycled plastic or paper containers like yogurt cups, small milk cartons, or egg cartons work well as small, indoor seed beds for carnations. Potting soil formulated for growing seeds or potting mixes designed for flowers both work well as the growing medium for carnation seeds.
The containers for starting carnation seeds should have a few holes poked in the bottom to allow for drainage. Combining the soil blend with a small amount of water will help keep the dirt in one place and make it easier to cover the seeds. Spoon soil into each cup, then add a few carnation seeds. Top the seeds with a sprinkling of soil, then put in a sunny, warm location. Covering the pots with a loose layer of plastic wrap or with a clear, inverted plastic container will keep the seeds moist and warm.
Once the carnation seeds sprout, the plastic wrap or lid can be removed, and the seedlings can be placed in a sunny room or window. It will take from three to five days for carnation seeds to sprout, depending on how warm they are and how much light they receive. Each cup will have multiple seedlings, and can be thinned out a few weeks after germination.
Once the carnation seedlings are about 2 inches tall, thin them out by pulling all but the biggest seedling in each pot. If the seeds have been planted in a single pot, thin them out to one big seedling every 2 inches. The rejected seedlings can be discarded or added to a compost pile. Allow carnation plants to grow inside until they are about 5 inches tall.
Let the carnations grow indoors until any danger of frost has passed. Every region is different, so consult a zone map to be sure the seedlings don't go outdoors before the frost date has passed. The carnation plants can be placed outdoors during the day to harden up and brought inside at night as needed until the frost date passes.
Choose a sunny garden location and transplant the carnation seedlings. Plant the carnations about 12 inches apart and water as needed; they require a minimal amount of care to survive. Expect to see blossoms throughout the spring and summer, and for those blossoms to taper off in early winter. Carnations are perennials, so they will grow back each year without further seeding.