Asked what we'd suggest the new owners do to this landscape we said, "Let's cut these yews way back."
"Can we do that?" They asked. "Will they grow back?"
Probably. If they don't, all we will have lost is a short wait to see how vigorously they sprout. If they turn out to be duds, no worries -- we would have had to cut them down to dig them out, anyway!
The best time to make such a hard cut is in late winter or very early spring. However, we made one cut in right away, to eliminate the driveway-encroaching yew at the end of the line.
("Best" is subjective. We like this timing because fewer people notice an absence then and the time between cut and new growth tends to be shorter.)
The directions on that photo are: Cut the bush down to a nice spray of branches maybe 18" tall and wide. (The yellow-green arc is created by making the cuts at the blue lines.)
Cut out any thin branches (red lines) to leave only stout limbs.
If there are green sprouts within a reasonable reach above the 18", cut to just above the sprout. (See one already cut, blue arrow.) Make clean cuts with a sharp saw.
We have confidence that these yews will sprout from the bare wood because they were still producing sprouts deep in the shady interior, albeit a scattered few. We asked the owners to hold off cutting the yews back until late winter, to avoid exposing these precious interior buds to winter's worst. Sheltered as they were by the thick shrub above, they may have failed to develop the cold hardiness outer branches acquired during fall.
By mid-May, perhaps three weeks after unmolested yews in the area have broken bud to resume growth, these bare branches will push out new greenery. Or not!
Many years ago we had the pleasure of meeting internationally renowned horticulturist Ralph Shugert, then working at Zelenka Nursery in Grand Haven, Michigan. Zelenka's was the largest grower of yews in the country. It was a fortuitous meeting, as we were pursuing information about pruning yews. Our experience seemed to contradict what we read in books and we figured anyone associated with the production of a million yews ought to be able to rule one way or the other.
To all our questions about cutting yews, Shugert had one beautifully succinct answer, "Just cut them!" No matter what condition, situation or timing we added in a new question, the answer was always the same.
Delighted to know that our field observations were being upheld, but wanting one more assurance, Janet asked, "So what about the best time, if you had a choice when to cut a yew back..."
Shugert's reply, "If you think we can prune fields full of yews all at one perfect time, you're dreaming. Just cut them!"