The Germination of Periwinkle Seeds

Germination

• A seed is germinating when the plant begins to grow, extending roots and leaves. Catharanthus requires a warm, moist environment to germinate. The Colorado State University Cooperative Extension recommends the following steps: Sow seeds indoors 10 to 12 weeks before the average time of the last frost. Fill a shallow tray with seed-starting mix, moisten and let drain. Sow seeds in rows and cover with 1/4 inch of the mix, then press down lightly and moisten the surface with water. Because Catharanthus requires total darkness to germinate, place the container in a black plastic trash bag. Keep the tray in a location with a temperature range of 65 to 75 degrees Fahrenheit. Roots and leaves will emerge in two to three weeks, according to Cornell University Home Gardening.

After Germinating

• When germination begins, remove the plastic bag and place the container in a sunny window in a location at 70 degrees Fahrenheit or higher. Avoid overwatering -- Catharanthus likes dryer conditions -- and water only when the planting medium dries but before the plants wilt. To help seedlings thrive, the Colorado State University Cooperative Extension recommends the following steps: Fertilize approximately 10 days after germination with a water-soluble fertilizer low in phosphorus and with most of its nitrogen from a source other than ammonium nitrate. When seedlings are about 2 inches tall, cut down all but the strongest plants, and plant those in flats approximately 2 inches apart. When three to four true leaves sprout, transplant to individual 2 1/2-inch pots . Place in a sunny location, and fertilize after two weeks. Transplant outdoors when soil and air temperatures remain above above 65 degrees Fahrenheit.

Uses

• Catharanthus takes longer to flower when started from seed, compared to plants from garden centers. It produces small flowers in soft hues ranging from white, salmon and lavender to rose-purple and bicolor, with shiny deep green leaves. Catharanthus flowers throughout summer, including its hottest weather, until frost. The plants grow in a rounded mass, 1 or 2 feet in height and width, although some newer varieties are wider and lower.

  Catharanthus requires little maintenance and works well in beds, borders, containers and as ground cover.

Planting

• Plant Catharanthus in slightly acidic, well-draining soil with a pH of 6 to 6.5 in a location receiving full sun -- six to eight hours a day -- plus some midday shade in the hottest regions of the country. It tolerates clay and sandy soils. Dig the bed to a depth of about 6 inches, and add a 1-inch layer of compost. Set plants in the ground at the same level they were in the pots, and firm soil around the roots. The Colorado State University Cooperative Extension recommends spacing plants 8 to 12 inches apart for border edging, at 6 to 8 inches for ground cover and at 12 to 14 inches for naturally trailing varieties. Keep Catharanthus on the dry side -- not watering more than two or three times after planting -- to prevent root rot, the University of Florida Cooperative Extension Service recommends.