Selfsufficientish.com

I dug up a rhubarb to move elsewhere and found that the root was enormous, like three large carrots close together. The top bit is like a bunch of white buds with brown papery stuff around. I expect it's quite a mature plant. Rather than dig a very deep hole to put it in, can any amount of root be removed and if so, does it need to callous over before planting?

you can trim a bit of the root off, you could also divide the plant up, as it is perennial into two or more sections to replant if you wish to increase your stock. It can be planted straight away after splitting or trimming. Put some good muck in the planting hole and make sure the buds are above the ground, you can give it a good mulch with some well made compost or rotted woodchip

Yup, what she said, although I have to admit to never having much success transplanting it.

Seperate the crowns, re-plant at least 3ft apart along with plenty of (preferably) home-made compost. Be mindful of any incoming cold weather. ....... make some custard, and bobs yer uncle!