Don’t rush to put out vinca plants in the spring. Plants set out too early in cold, wet soil will deliver a sickly performance; after all, these are hot weather annuals. A safe bet is to plant your vincas around the same time you set out your tomato transplants: when evening temperatures average 60 degrees Fahrenheit. Full sun is best, although some afternoon shade is fine, especially in hot southern locations.
Annual vinca is best grown in a sandy loam soil in a full sun location. Although tolerant of drought, it will perform best with weekly water soaked in rather than sprayed from overhead. Vincas are free-flowering and self-cleaning, and no deadheading is necessary.
This is one of the most carefree annual flowers you can grow, with few serious disease or insect problems. In poorly draining soil, stem rot and leaf spots may occur.