Celosia, commonly known as cockscomb or plume flower, is an annual celebrated for its vibrant colors and flower textures. Since these plants are sensitive to cold, starting them indoors is an effective method to ensure a long, successful blooming season. This guide provides the process for successfully starting Celosia seeds inside your home until they are ready for the garden.
Preparing for Seed Starting
Celosia seeds should be started indoors approximately six to eight weeks before the average last expected frost date. This timing allows the seedlings to reach an appropriate size for transplanting once outdoor conditions are reliably warm.
Gathering materials beforehand is helpful. You will need a sterile seed starting mix, which is lighter and finer than regular garden soil, along with clean planting trays or containers. A plastic humidity dome and a heat mat help create the ideal environment for germination.
Step-by-Step Indoor Sowing
Thoroughly moisten the seed starting mix before placing it into the trays. The mix should be damp, like a wrung-out sponge, but not waterlogged, which prevents seeds from being washed away during initial watering. Celosia seeds are small and require exposure to light to trigger germination.
Because light is required, the seeds should be surface-sown directly onto the prepared soil mix. You may cover them with a light dusting of fine vermiculite or soil, ensuring the covering is no more than an eighth of an inch deep. This helps anchor the seed without blocking the necessary light. Aim to space the seeds roughly one to two inches apart within the tray.
After sowing, cover the tray with the humidity dome to trap moisture. Place the covered tray on a heat mat to provide warm temperatures, ideally between 70 and 80 degrees Fahrenheit (21 and 27 degrees Celsius). Within eight to fourteen days, you should observe the first sprouts emerging.
Caring for Young Celosia Seedlings
Once the first seedlings emerge, immediately remove both the humidity dome and the heat mat. Keeping young plants too warm or humid after sprouting encourages fungal diseases, such as “damping off.” At this stage, the seedlings require a strong light source to develop compact stems.
Place the seedlings directly under a grow light, positioning the source just a few inches above the foliage. Provide strong light for fourteen to sixteen hours daily to prevent the plants from stretching excessively, a condition known as etiolation. This promotes the development of thick, sturdy stems.
Use bottom watering by placing the tray in a shallow container of water for about 15 minutes, allowing the soil to wick moisture upward. This encourages deeper root growth and keeps the soil surface drier, preventing fungal issues. Once the seedlings develop their second set of true leaves, they are ready for thinning.
To thin the plants, snip the weaker seedlings at the soil line, leaving only the strongest plant in each spot. This practice ensures adequate air circulation and reduces competition for nutrients. When the seedlings are about three to four weeks old, begin feeding them with a half-strength, balanced liquid fertilizer.
Hardening Off and Transplanting Outdoors
Before moving Celosia outdoors, they must undergo hardening off, which acclimates them to outdoor conditions. This process toughens the plant tissues, preparing them for wind, sun, and fluctuating temperatures. Begin hardening off seven to ten days before planting, after all danger of frost has passed.
On the first few days, place the seedlings outside in a shaded, sheltered area for only one to two hours, protected from strong wind. Each day, increase the duration outside and gradually expose them to more direct sunlight. After about a week, the Celosia should tolerate a full day outside, provided nighttime temperatures remain above 50 degrees Fahrenheit (10 degrees Celsius).
The final planting location should receive full sun for at least six hours daily. Celosia thrives in well-draining, moist soil rich in organic matter. When transplanting, carefully remove the seedlings from their trays and space them six to twelve inches apart, depending on the variety. Immediately water the newly transplanted Celosia to settle the soil around the roots and reduce transplant shock.