...as gardens strip down for winter. The spotlight swings their way as perennial foliage falls and deciduous shrubs become see-through. Often, now is the time we see evergreen problems overlooked while the focus was on spring and summer.
If you notice leafless or brown parts on evergreens now, the first thing to do is check for breakage. Follow the bare- or brown branch back into the plant. Look for splits or tears. If you find damage, prune below it. Don't waffle, just prune. A healthy plant will fill the gap in time. Left cluttered, it won't grow as much new green or may not grow at all into a shade-casting tangle of dead wood.
...yet most or all of the leaves are dead but still clinging, suspect fumes, urine or another burning- or drying substance. (Urine burns by its saltiness, pulling water out of leaf tissue.) Look for proof of life in that branch, just as we do in late winter when we suspect die-back from cold. That is, do a scratch test to determine if the cambium below the bark is still moist and green. Cut back to live wood.
Some evergreens grow back from leafless wood
Yew, boxwood, euonymus, holly, rhododendron and other broad-leaf evergreens are like deciduous shrubs. As long as there is live cambium, even without any foliage, that branch can generate new growth. Cut the branch back to good wood and wait.
Most needled evergreens (pine, juniper, arborvitae, falsecypress, fir and spruce) are not usually able to sprout from needle-less, bud-less wood. Even if such a plant's wood passes the scratch test you are probably going to have to cut out that branch. Prune back to a side branch that still has foliage or moist tip buds.
Hard to do? Unsure? You can leave the branch until the end of the next spring. If it has not pushed out new greenery by then, it’s not going to.
If the dead spot you see has twigs with off-color streaks or sunken spots, that’s not a good sign. Fungi that infect weak or young wood can leave such marks on and in wood. If you see discolored wood, search the Internet or the index of a plant disease book for “(scientific name of your plant) discolored wood." On the Internet, select an image search and scan for branches that resemble what you found in your yard.
Let’s prevent their weakening and decline in the first place!
Breakage, disease and leaf-killing pest problems have something basic in common. Poor pruning contributes to all these problems, and many people have no clue that their pruning technique fits this description.
Let a single branch speak for the whole shrub
In this case we are looking at boxwood but it can speak for yew, juniper, arborvitae, privet, burning bush and others subjected to constant shearing.
We're comparing branches from a boxwood clipped once a year, and thinned to a branch from a boxwood repeatedly sheared without regular thinning.
Boxwood, yew, juniper and other shrubs are shear magnets. Gardeners shave the outer edge with shears but never thin the interior. Year after year, the shorn tips respond by branching in a predictable, deadly pattern: Nip the tip of one twig with one leaf and it sprouts as two thinner twigs with smaller leaves. Two shorn tips grow back as four, then eight, all those twigs occupying the same amount of space that is, rightfully, one single twig's space at the outer edge of the plant.
Now the interior of the shrub becomes crowded with wood. Its depths are too dark to support leafy growth. Foliage, the plant’s power source, is scarce. The plant has developed a high wood-to-leaf ratio, with too little greenery to keep all the wood healthy. Woody parts above and below ground weaken. Weak, nutrient deficient wood and leaves become less able to deter insect- and pest organisms. As pests proliferate, that saps even more energy.
No wonder these shrubs show brown.
Follow this link to see a boxwood pruned well and another being reclaimed from abuse.