I have plenty of periwinkle (probably Vinca minor, or possibly V. major) in my back yard. I will soon attend to building a storage shed there. I would have to clear periwinkle for the shed ground. I would like to transplant that periwinkle to a sloping part of my front grassy/weedy yard that causes me headaches when moving. How do I perform this operation and when is the best time to do that? I am talking about western Pennsylvania.
You will need to dig out the Vinca with roots attached in order to tranplant it, and you should only do that when the winter is over and the ground is not frozen. If the area you want to transplant to dries out frequently during spring/early summer and you are unable to irrigate it frequently until they are established, it's probably best to pot up rooted sections, cut them back to an inch or so and let them grow sufficiently to form a good root system before planting them out. If you transplant to the ground immediately, ensure you have dug over the area where you want to move them to first, cut back the top growth to about 1 or 2 inches, then water in well after planting. You will obviously lose the flowers this year, but they may produce a few later on.