I have not transplanted a yucca that has grown in place from seed; container grown specimens transplant beautifully even many years later. Recurvifolia doesn't even need roots, it will regenerate new ones. I have not worked with elata. My advice is to wait until mid-spring. Of course you'll want to have your holes dug before digging the elatas. In my opinion, if you have to cut the taproot, the yucca is going to be set back no matter what you do. A bunch of water is just asking for rot IMHO. I would not water until it had been very hot and dry for several weeks. Then soak it well and don't water again until it totally dries out again. Maybe 5 deep soakings over the course of the summer. No more after August. I believe I read that skinny leaved Yuccas are apt to die back if transplanted but they should quickly recover next summer because by then they will have a good root system.
Of course I live in the Mississippi River valley. It is very humid, rains a lot and the soil is heavy. And admitedly I have not worked with elata.

Hi Fred, Thank you for your reply. I certainly will have the new hole ready before digging up each yucca. Normally I wait about a week before watering newly planted cactus or succulents. Unless it is winter or July-August, the soil here is generally very, very dry. I suspect that the reason the link mentioned success only if watered immediately after transplanting was because the relocations studied were due to highway construction projects and that was the only water those yuccas would receive prior to the next rainy season.

I am especially curious if anyone knows how deep the taproot on a young (1-2 foot tall) elata would be. The link suggests 3 to 5 feet but implies that is for an adult 9 to 12 feet tall.

Thanks,
Anna

Here is a link that might be useful: Species - Yucca elata