How and when is the best time to move plants?

You can separate these tubers after they bloom this spring. Dug them up and slice them at the roots. Replant...space them at least a foot apart since they propagate quickly. Make sure each section has a decent amount of roots before covering with soil and water well.

https://homeguides.sfgate.com/transplant-tiger-lily-46116.html

The best time to transplant any plant, is when it's dormant. Late fall, early spring, etc.... Irises ( if they like where they are) will spread like crazy! Even after you move them, you probably will have stragglers come back. Just keep digging them out, as they do.

Those are gorgeous but definitely need to be thinned out! Fall is the best time and don't expect a lot of blooms the first spring after you move them. Add some food while you are placing them.

I did that to some day lilies and never saw them again. I don't know what happened. I should have left them alone.

What about indoor bamboo when can I do it? I did it in spring but it just isn't doing very good now.

As both flowers spread, you can attempt to dig out individual plants and move them as you wish. It's likely that you'll lose some along the way.

If it were my garden, I would attempt to move some of the lilies as they are pretty hardy. But - I would actually ignore most of the mixture as the irises will be long gone shortly while the lilies will continue until fall. Irises are only in the spring.

Happy growing! 😎💐

Where warm seasons are shorter, it is best to leave them until they are into the late fall and the green leaves are brown and they are no longer growing. Separate the roots and bury them tops up, water them, and if in winter it does not rain/snow, give them more water. Many plants are only truly dormant a short season and do need water in winter.

I had the same problem , day lilies were taking over. Neighbor who can grow anything, showed me how to trans plant in early spring never lose a plant. Dig a large hole put in miracle grow add top soil then lilies. Cover well with top soil and then mulch real good. Then cover until plant are growing well. My lilies are still covered and doing well. I live in NC and looking forward to beautiful flowers come early April.

I agree with Jessica, early spring or late fall. You can transplant at other times, but avoid the hot weather--that's really stressful for most transplants.

I transplanted an asiatic lily as soon as it was a couple of inches tall. I placed it in a fenced garden (away from rabbits) and it bloomed that year. I divided up my bearded iris a couple of months ago when we had temps in the 70s. I had a huge clump and divided them up, cut off any that appeared to have border damage and planted them all over my front yard. I also gifted several to neighbors. Make sure you cut the leaves down to a few inches so the energy goes into them rooting as they come into season.