Q.Can Flowering Vinca Planted Last Year Be Cut Back In The Spring To Bloom Again?
I live in Phoenix, AZ. I planted white vinca with a red center in a flower bed which gets full sun. It is late January, and it is still blooming, although the blooms are smaller. If I cut them back in March, and apply Miracle Grow, will the continue to bloom this summer? I have had luck with vinca in pots by doing this.

Certified GKH Gardening Expert
Yes, vinca is perennial in your area so it should continue to bloom. It will benefit from shearing and fertilizer as you suggest. Here is more:
https://www.gardeningknowhow.com/ornamental/flowers/annual-vinca/madagascar-periwinkle-care.htm