Dianthus, a genus including popular garden varieties such as Pinks, Carnations, and Sweet William, is valued for its fringed petals and spicy, clove-like fragrance. These flowering plants are a staple in perennial borders and containers, offering a diverse range of colors and forms. Propagating dianthus allows gardeners to multiply a favorite variety, preserve the exact traits of a hybrid plant, or increase the number of flowers in a landscape. Propagation can be accomplished through seeds for genetic variation, or via cuttings and division for cloning the parent plant.
Starting Dianthus from Seed
Propagating dianthus from seed is the most common method, especially for annual and biennial types. Seeds are best started indoors six to eight weeks before the final frost date. Fill trays with a sterile, moist seed-starting mix that is well-draining yet retains moisture. Dianthus seeds require light for germination, so press them lightly into the surface and cover with only a very thin layer of fine vermiculite or soil.
Maintain a consistent temperature range of 65–72°F (18–22°C) for quick results, with germination occurring within seven to fourteen days. After seedlings emerge, place them under grow lights or in a sunny window to prevent them from becoming elongated. Once the seedlings develop their first set of true leaves, they can be carefully transferred into individual cells or small pots to promote continued growth.
Propagating via Softwood Cuttings
Taking softwood cuttings is the most reliable vegetative method to clone perennial dianthus varieties, ensuring the new plants possess identical characteristics. The best time to take cuttings is during mid-summer, selecting non-flowering shoots from the current season’s growth. Use a sharp, sterilized blade to take a two- to three-inch cutting, making the cut just below a leaf node.
Strip the leaves from the bottom half of the stem to prevent rotting once inserted into the rooting medium. Dipping the cut end into a powdered or liquid rooting hormone can accelerate root formation and increase the success rate. Insert the prepared cuttings into a highly porous medium, such as perlite and peat moss, ensuring at least one bare node is beneath the surface.
To maintain the high humidity necessary for rooting, place the tray of cuttings inside a clear plastic bag or a mini-greenhouse setup. Position the cuttings in a bright area that receives indirect sunlight. Intense, direct sun can scorch the foliage before roots have formed, but new roots typically develop within six weeks.
Clump Division and Simple Layering
Clump Division
Clump division is a practical method for mature, clumping dianthus varieties and revitalizes older plants dying out in the center. This process is best performed in early spring before new growth begins or in autumn after flowering concludes. Carefully dig up the entire plant, securing as much of the root ball as possible.
Separate the root mass into smaller sections using a sharp knife or clean spade, ensuring each piece retains healthy roots and foliage. Replant these divisions immediately at the same depth as the original plant, then water thoroughly to settle the soil. Dianthus benefits from this division every three to five years to maintain vigor and prolific blooming.
Simple Layering
Simple layering offers a method for propagating new plants directly in the garden, most effective in midsummer. Select a long, flexible, non-flowering stem and gently bend it down to touch the soil near the parent plant. To encourage rooting, make a small, shallow cut lengthwise through a node where the stem meets the ground. Secure the wounded section to the soil with a landscape pin or hooked wire and cover it with a light, well-draining soil mix, leaving the stem tip exposed.
Caring for Newly Propagated Plants
Once seedlings or rooted cuttings are sturdy, they must be gradually prepared for their permanent outdoor environment. This acclimatization process, known as “hardening off,” involves incrementally exposing the young plants to outdoor conditions over seven to ten days. Initially, plants are placed in a sheltered, shaded location for a few hours daily, slowly increasing the duration and exposure to sun and wind.
When the risk of frost has passed, transplant the hardened plants into the garden or larger containers. Set the plants so the crown sits level with the surrounding soil to prevent stem rot. Immediately after transplanting, deep watering is necessary to mitigate shock and help the roots establish contact with the soil.
For the first month, maintain a consistent watering schedule, ensuring the soil remains moist but never waterlogged, as dianthus is intolerant of soggy conditions. Seedlings benefit from a diluted, balanced liquid fertilizer every two weeks starting ten days after emergence. Established perennial dianthus require only a single application of slow-release or organic fertilizer in the late spring to fuel their seasonal display.