Vinca, scientific name Catharanthus, has the common names periwinkle and Madagascar periwinkle. Vinca minor and Vinca major, which resemble periwinkles but are technically different plants. Vinca flowers during the summer months and grows either upright or as a short vine. Because of their intolerance for cool temperatures, vinca seeds must be planted indoors in the early spring and transplanted outdoors once temperatures warm.
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Wait until 10 to 12 weeks before the last-expected frost in your region to sow the vinca seeds.
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Fill a seed tray with a specialized seed-starting potting soil. Fill each compartment until it is 3/4 full of the mixture.
Water the soil mixture until it is damp all the way to the bottom of each compartment.
Place three to four vinca seeds on top of the soil in each compartment and then cover all of the seeds with another 1/4-inch layer of the soil mixture. Press down gently on top of the soil with your fingers.
Fill a spray bottle with water and spritz the top of the soil to moisten it until it appears visibly damp.
Insert the entire seed tray into a black trash bag and set the bag on top of a heat mat. Plug in the heat mat and set the thermostat to 77 degrees F.
Wait until the seeds germinate which takes approximately one to two weeks. Remove the heat mat and the trash bag and place the seed tray in bright sunlight.
Water the soil only when it is completely dry to the touch.
Apply a 10-4-3 liquid plant fertilizer 10 days after germination using the amount specified by the manufacturer.
Transplant each seedling to a 2 1/2-inch diameter plant pot when it reaches 2 inches tall. Place the pots back into the sunny location.
Transplant the vinca plants outdoors when soil temperatures rise above 65 degrees F.