The Best Time to Propagate Periwinkle

Seed

• Propagate periwinkle by seed in the early spring, as soon as the soil warms to at least 65 degrees Fahrenheit. Carefully prepare the garden bed before planting your periwinkle seeds. Till 3-inches peat moss, 3-inches leaf mold and 1-inch perlite or coarse horticultural sand into the soil to a depth of 6 inches. Rake the garden bed to a smooth finish and apply 1/2-inch water to lightly moisten the soil. Sprinkle the periwinkle seeds evenly over the surface of the soil. Maintain slightly moistened, but never soggy, soil to encourage the seeds to sprout.

Division

• Divide periwinkle plants in the spring or early fall, when temperatures are cool but hard frosts are unlikely. Irrigate the garden bed the day before dividing your periwinkle to soften the soil; apply up to 1 inch of water. Dig the periwinkle, keeping your hand shovel or spade about 4 inches from the base of the plant. Use your hands to gently brush the soil from the root ball. Divide the root ball into sections; each section should have three to four healthy stems. Plant the periwinkle divisions in your garden bed. Amend the soil with peat moss, compost and perlite if necessary to improve nutrition and drainage.

Cuttings

• Propagate periwinkle from cuttings in spring, after the threat of frost has passed. Use sharpened and sterilized pruning shears to take 4 to 6-inch cuttings from a healthy periwinkle plant. Dust the cut end of the periwinkle cuttings in a powered rooting hormone and plant in individual 4-inch pots filled with sterile, well-draining potting soil. Place the pots in a sunny site and water the cuttings frequently to keep the potting soil moist. Transplant the cuttings to your garden bed once they've formed strong root systems and present 2 to 3 inches new top growth.

Layering

• Though the ideal time to propagate periwinkle plants by layering is in the late spring or early summer, gardeners can use the layering method successfully any time the plants are actively growing. Bend one or two periwinkle stems over so that they touch the surface of the soil and secure them there using paperclips. Straighten paperclips into a "U" shape and insert them into the soil at every other leaf joint; the paperclips should press the stems firmly to the soil, but not so firmly that they cut into the stems. Maintain moist soil while you wait for the stems to root. Cut the stems on both sides of the rooted sections and transplant the plantlets to other locations in the garden bed, if desired.