Dottie,

The optimum time for root pruning a decideous tree is before it starts to leaf out in spring.

Can you do it now? Yes. You can do it now, but after you prune it, you must keep it in the shade under trees for at least a week and water throughly. Quick Start from Miracle Grow wouldn't hurt it either.

Then after a week, gradually start to expose it to sun, and that is if it perks up and shows growth. It should be OK if you really think it must be done now.

If you don't prune it it might decline in health, so I would do it.

Thanks , butterfly , but I think this is going to be a multi-stage project of first tipping off the top of the standard and root pruning the sector away from the foundation. I'll leave it in place watching for droop and re-direct the downspout to avoid flooding the pruned root portion. That way it retains 2/3 of its root system until I'm ready to begin removing half the standard. I'm just afraid taking off the entire standard will encourage regrowth of the ordinary ginkgo to the detriment of the tube leafed ginkgo.

I'll probably do as you recommend and finish the full root prune after leaf drop in fall and begin the lift and transfer to a new site in March of next year.