If your yews are old, have been shorn repeatedly so they have little depth to their foliage layer, and have been allowed to creep 'way beyond their bounds, they may take a year or two to complete recovery from a cutback.
We present these photos to help you decide whether you can wait while old yews recover. Please note: We don't always wait when plants make a slow comeback but in this situation it worked out that way and we took the lesson as a bonus.
The whole story follows, with additional images.
Clockwise from upper left: August, the next April, very early spring 30 months after the initial cut, and 30 months plus two hours later.
We said to our client, "You're right, this front foundation needs help. But rather than starting over with new plants let's see how these well established yews respond to a cutback." So we cut back hard, doing the work in late summer (mid-August) because that's when we decided to deal with this problem.
Why?! You might say. Those are as ugly in a new way as they were when they were overgrown!
A trial cut is almost always worthwhile. It's no extra labor -- we must cut up the shrubs even if we dig them out. The only difference is that if we wait for spring before we dig, we often see gangbuster new growth. However, if the cutback yews produce only a few new shoots a month after spring's sprung, and we don't want to wait, then it's time to buy new and start over.
We knew that by late spring -- about a month after a yew's normal first flush of growth -- we would see whether the shrubs began to fluff out with lots of new growth or planned to revive more slowly.
Most of these yews pushed out only enough new growth that first spring to show us intent to come back.
Some were very slow. Conveniently, they were at the front walk. Knowing we would not be able to remake the entire front foundation at one time, we had decided to focus on the front walk. We dug out the slow-pokes.
In year two after the cut, spring came earlier than it ever had. The warmth fooled even established native plants to leaf out a month ahead of schedule.
On the yews, lots of dormant buds sprouted.
Then, a freeze came. It killed all the foliage on many plants, including most of the new growth on these yews. It swamped us with work in every garden -- protecting, replacing, cutting back damage. So the remaining yews stayed in place, managing to pick up their growing pace only a little.
Cool weather and lots of rain in early summer coaxed these and other yews into a pretty fine second flush of growth. We said, "Well then, you're beginning to look good," and left them to it, simply making some cuts to thin more of the densest branched sections.
Unfortunately, the good times didn't last. That summer set records as the hottest ever for the continent. Some areas, ours included, suffered drought as well. This fried many plants, including the new shoots of yews everywhere. Ma Nature cut back our trial yews a second time that year.
Meanwhile, the work made by freakish weather tied us up so these yews remained in place. We simply clipped to remove all the dead tips.
Spring came late but when it did we said, "How about that!" Dormant buds appeared in abundance along the branches. (Right.)
We cut to keep the shrubs within bounds and made more thinning cuts to encourage dormant buds even lower on their ankles. By the end of this summer -- ongoing as we write -- these will be fine specimens and we'll update this photo story.
Below, early spring, 30 months after cutback.
Above, right: If these shrubs seem too bare, look again at that low windowsill, and check this example of what we know plants can do when we cut back hard regularly with an eye to keep a plant small and also dense.
Below: For comparison. Here they are again when just cut back, for comparison to the photos above that were taken 30 months later. Notice below that the shrubs' foliage was at and above windowsill level. The thinning we did during the otherwise-unproductive intervening years promoted foliage lower on the stems. By fall they will probably be full to the ground with leaves and buds.
One last note: Don't fall back into shearing-only after you rejuvenate or replace yews. Be sure to begin right away with the right kind of pruning whenever they reach the height or width you can allow.