I just spent the day moving perennials from my holding bed to other display beds. The saying is if it blooms in the spring move in the fall. If it blooms in the fall, move in the spring. That said, I move plants whenever I want them somewhere else. Try to take as much soil as possible to lessen transplant shock. Plants may wilt or sulk a bit for a few days but if they are kept watered they should be okay.

Sedum, hens & chicks, and creeping thyme all have shallow roots and will move well. Some plants do not like to be moved at all, ie those with a deep tap root.

When it comes to move the plants or lose them, I say move them. If some don't survive, well, they would have been lost anyway. Most will survive with a bit of TLC.

We built a deck on the front of our house last summer in late July. I had to move ALL sorts of perennials during the hottest part of the summer and everyone survived. Just make sure you water them well after the move and keep an eye on them for the first few weeks. But most perennials are pretty resilient.

Kristy :)

I also move things whenever I need to. Try for a cloudy, cool day or at least late afternoon or early evening. Water the plant well earlier that day. Dig the receiving hole first, move the plant, water well. One of the reasons you are watering is to eliminate air pockets around the roots --- roots in air will shrivel up. Protect from sun the next day and water some more. Another thing that can help with some plants is to remove some of the larger, older leaves or even to cut off a third of the plant. Mulch.

Remember that if you dig up and fluff up the soil at the bottom of the planting hole, it will settle and the plant will sink down a bit. So if you have to dig into the soil under where the plant will go (for instance because you have to incorporate compost because the soil is poor), try to correct for this up somehow, perhaps by watering the hole earlier in the day, by pressing the fluffy soil down, or by planting the plant a little high to compensate.

I only fuss this much with plants I think will be sensitive or that I really care about or that will be planted in full sun.

I always move them when it is convenient for me as well. And watering well is the key.

One additional tip I would add is when you dig the new hole, fill it with water. Then let the water sink into the surrounding soil (at least half of it) before setting the transplant in.
This trick never fails me!