Approach grafting: best period to remove the donor plants

Helllo everyone. I have done approach grafting of itoigawa donor plants on a couple of receiving junipers that needed a better foliage. What is the best period to remove the donor plants? Is it the fall, when the plants grow their vascular system, or is it the spring when they exit dormancy and boost the growth of their foliage?

It really depends on how well are the grafts established IMO.
I’ve removed some in fall in spring and in summer before or after the peak summer heat. I didn’t notice any difference.
Best bet is in spring when they are growing and can start healing right away.
If they already have winter color set in or if you’re expecting frosts I’d wait 'till spring.