Ok, so it’s time to prune yews…how do you know? Just look at the shrub/hedge. At this time of year, you’ll see lots of lighter color shoots at the ends of the stems. If you want to keep the size the same, (and most of us do), now is the time. So, how to do it?
First, here’s how NOT to do it. The “easy button” method is getting out the hedge shears, plugging it in or pulling the rip cord and doing your best to make all the growth even, neat and trimmed. While this is the only real way to prune Christmas trees, it’s a really poor way to prune shrubs, including yews. Why? Unlike Christmas trees, which are crops to be grown and sold in 7 years, shrubs are long term investments in a landscape. Shearing them means making indiscriminate cuts at pre-determined locations, whether there is regrowth potential at that point or not. This technique almost always leads to the death of the stems, not the proliferation of balanced, healthy new growth.
Instead, the best approach is to THIN the stems. Using a hand pruners, reach into the shrubs’ periphery and make individual cuts just above where a new stem has started its growth. Now, here’s the most important point – endeavor to make cuts at various levels in the canopy, not at the exact same height. A typical set of pruning cuts would be at 3 inches, at 8 inches, at 15 inches, at 5 inches and other lengths away from the ends of the stem growth, depending on where new growth has been identified.
Why thinning and not shearing? – Two reasons. One, much, much less injury will occur to the yew as a result. If a mistake is made on the location of the cut, enough green material remains in the plant to cover up the “hole” that is made. This is not the case with shearing, where little viable tissue remains in some to most cases. Second, a natural and varied look is produced, which is appropriate for most landscapes.
If a formal appearance is desired, then shearing is the only way to achieve it. The damage to the shrub from shearing can be minimized by making the cuts such that the top of the hedge is narrower than the bottom, so that adequate light can be received by all parts of the plant, giving the bottom a chance to remain growing, instead of being shaded by the top. Also, the technique of varying the height of the cut can be used to help lessen the impact of the shearing.