Can I prune periwinkle plants
I purchased a type of periwinkle plant that can withstand full sunshine and was told to plant them 6 inches apart. I have done that, but the plants look rather tall and skinny. If I pinch off the top, will the plant bush out to full plants? I don't want to kill the plants.
Yes, you can trim your plants.
It seems like your plants just need a bit more time.