Red Creeping Thyme (Thymus serpyllum ‘Coccineus’) is a low-growing, mat-forming perennial known for its dense, dark green foliage and red or magenta-pink flowers. This aromatic ground cover releases a pleasant, herbaceous scent when brushed or walked upon, making it popular for rock gardens and paths. Planting this variety from seed requires specific conditions, as the tiny seeds need light for successful germination. Starting these slow-growing plants indoors provides the controlled environment necessary before they are ready for the outdoor climate.
Preparing the Planting Environment
The success of Red Creeping Thyme depends on selecting and preparing the location. This Mediterranean native requires a full sun location, receiving at least six hours of direct sunlight daily to promote dense growth and flowering. While it tolerates partial shade, insufficient sun reduces the intensity and abundance of blooms.
The plant thrives in lean, well-draining conditions and is prone to root rot in heavy ground. The soil should be sandy or gravelly loam with a neutral to slightly alkaline pH (6.0 to 8.0). Amending a compact or clay-heavy site with coarse sand or fine gravel improves drainage and mimics the plant’s preferred rocky habitat.
Seeds should be started indoors six to ten weeks before the average last frost date. This early start is necessary because the seedlings develop slowly, requiring a longer period of sheltered growth before transplanting outside.
Starting Thyme Seeds Indoors
Select a clean, shallow seed-starting tray and fill it with a sterile seed-starting mix. Using a sterile medium prevents “damping off,” a fungal disease that destroys young seedlings. The mix should be thoroughly moistened before sowing to maintain consistent moisture levels during germination.
The tiny Red Creeping Thyme seeds must be surface-sown, as they require light (photoblastic) to germinate. Scatter the seeds lightly across the surface of the moistened mix and gently press them down to ensure good seed-to-soil contact without covering them. A light dusting of fine vermiculite can be applied to help retain surface moisture without blocking the light.
After sowing, use a gentle misting bottle to water the surface. Cover the tray with a clear plastic dome or plastic wrap to create a humid microclimate. Place the tray where the soil temperature is 65–70°F for optimal germination, which takes between 14 and 28 days.
Caring for Seedlings Until Transplant
Once sprouts emerge, remove the humidity dome to allow air circulation and prevent fungal growth. The seedlings require intense light to develop strong stems. Position the trays under a grow light system or in a bright, south-facing window.
Watering must be done carefully to avoid disturbing the root systems. Bottom watering, where the tray sits in a shallow pan of water until the soil surface is moist, is recommended. Alternatively, use a fine misting bottle to keep the soil consistently moist but never soggy.
When the seedlings develop their first set of true leaves, they are ready for thinning. Use small scissors to snip off the weaker seedlings, leaving only the healthiest plant in each cell or spaced about an inch apart. Providing good air circulation helps strengthen the stems in preparation for the outdoor environment.
Moving Seedlings Outdoors
Acclimating the plants to the outdoor elements is done through “hardening off.” This step prevents transplant shock, which occurs when seedlings are exposed to direct sun, wind, and fluctuating temperatures. The hardening off period should last seven to ten days, starting after the threat of the last frost has passed.
Begin by placing the trays outside in a sheltered, shaded location for one to two hours. Over the next week, increase the time the seedlings spend outdoors, introducing them to direct morning sun, wind, and cooler evening temperatures. This slow introduction allows the plant tissue to thicken and adjust.
After hardening off is complete, the thyme seedlings can be transplanted into the prepared outdoor location. Gently remove the plants from their containers, handling the root balls with care, and set them into the ground spaced six to twelve inches apart. Water the newly planted seedlings after transplanting to settle the soil around the roots.