When and how to transplant perennials?

Are they in pots or in ground? If in pots, you can transplant at any time to a bigger pot, and use the right soil keeping the rootball in tact. Depending on the plant, spring and fall are both good times to move in ground perennials. I would Google each plant to make sure you are providing the best care.

I usually transplant in early spring as part of my spring clean up ( I live in zone 5, southwestern Ontario ) but could also do it at this time of the year...I use the spring as a) the plants are smaller and easier to move and b) they then have the whole growing season to re-establish themselves in their new home.

I live in CA zone 9b and plant perennails both fall and spring depending on the plant and the weather. We only have a few months of rain so the ones I know need more water I plant in the fall so they can have a good start before I need to supplement their water more often. Succulents I plant in the spring. The big Sunset Garden book I find very useful for determining when, or even if I should plant something. It's really a useful resource because it has sections by zones as well as general plant info.

I live in the NE zone 5. You can plant and transplant at the end of the growing season. Spring is also another time to do the same. Make sure you give them water everyday after planted.