Coreopsis, commonly known as Tickseed, is a garden favorite celebrated for its extended bloom period and cheerful, daisy-like flowers. This resilient genus includes annual, perennial, and tender perennial varieties, offering a wide spectrum of colors from classic yellow and gold to pinks and reds. Coreopsis is prized for its adaptability and ability to thrive in sunny locations with minimal care. Increasing your stock of these plants can be achieved reliably through three distinct methods: starting from seed, dividing established clumps, or rooting stem cuttings.
Starting Coreopsis from Seed
Propagating Coreopsis from seed is an economical way to produce a large number of new plants, though the process requires careful management of light and temperature. For many perennial varieties, such as Coreopsis grandiflora or Coreopsis lanceolata, a period of cold stratification is necessary to break dormancy and trigger successful germination. This biological process mimics the natural winter cycle the seeds would experience outdoors.
To achieve this indoors, the seeds should be mixed with a damp medium, like sand or peat moss, placed into a sealed plastic bag, and stored in a refrigerator for approximately 30 days. Once stratified, or for varieties that do not require cold treatment, seeds can be started indoors six to eight weeks before the final expected frost date. Use a sterile seed-starting mix in trays or containers, ensuring it is thoroughly moistened before sowing.
Coreopsis seeds are minute and require light to germinate, meaning they should be surface-sown rather than buried deeply. Gently press the seeds onto the surface of the soil and cover them with only a very thin dusting of vermiculite or fine soil, no more than 1 millimeter. Maintain a consistent soil temperature near 70°F (21°C), providing 12 to 14 hours of supplemental light daily.
Germination can occur quickly, often within one to three weeks, provided the soil remains consistently moist. Once seedlings develop their first set of true leaves, it is important to thin them to prevent overcrowding, which improves air circulation and reduces the risk of damping-off disease. Before transplanting the young plants into the garden, they must be gradually acclimated to outdoor conditions over a period of seven to ten days in a process called hardening off.
Propagating Coreopsis by Dividing Mature Plants
Division is the preferred method for propagating perennial Coreopsis varieties, as it simultaneously increases plant numbers and rejuvenates older, less vigorous clumps. Perennial Coreopsis tends to be relatively short-lived, and division every three to five years helps maintain the plant’s health by preventing the center of the clump from dying out. The most opportune time for separation is in the early spring, just as new growth begins to emerge, or in the early autumn after the main flush of flowering has completed.
Begin by carefully digging up the entire plant, using a garden fork or spade to lift the root ball. Once removed, gently shake or rinse the soil away from the roots to better visualize the individual sections and growth crowns. A healthy clump should be separated into smaller pieces, each possessing a robust portion of roots and at least two or three new growth buds or shoots.
A clean, sharp knife or spade should be used to slice through the dense crown and root mass. The old, woody center of the original plant, which is unproductive, should be discarded. Immediately replant the newly separated divisions into prepared soil at the same depth they were previously growing.
The planting area should be amended with organic matter to ensure good drainage, as Coreopsis dislikes heavy, waterlogged conditions. After replanting, the divisions must be watered thoroughly to settle the soil around the roots and eliminate air pockets. Consistent moisture is necessary for the first few weeks to encourage the rapid establishment of the new root systems.
Rooting Coreopsis from Stem Cuttings
Propagating Coreopsis using stem cuttings guarantees the new plant is a genetic clone, which is particularly useful for reproducing specific hybrid cultivars. The best time to take these cuttings is during late spring or early summer when the plant is in a phase of active growth but before the stems have hardened into a woody state. Select healthy, non-flowering stems that are semi-softwood, meaning they are firm but still pliable.
The cutting should be a segment about four to six inches long, taken with a clean, sharp blade, making the cut just below a node—the point where a leaf joins the stem. Remove all but the top two or three sets of leaves to reduce water loss, leaving the stem bare below the foliage crown. Dipping the cut end into a powdered or liquid rooting hormone can significantly increase the success rate and speed of root formation.
The prepared cuttings should then be inserted into a sterile, well-draining rooting medium such as a mix of peat and perlite or coarse sand. Ensure at least one node is buried beneath the surface of the medium. The container should be covered with a clear plastic dome or bag to create a mini-greenhouse environment.
Place the cuttings in a location that receives bright, indirect light and maintains a warm temperature, ideally between 60°F and 65°F (15°C and 18°C). Roots will form within several weeks.