Privet hedges and what you need to know about them
I have a 54-year-old privet hedge that until recently has been growing very nicely on all sides. However, in the last two years, I have noticed that the sides are not growing new stems and are getting to be quite thin despite the fact that the top has always been narrower than the lower sides so they get good sunlight. I have not fed the hedge for years, relying on what I was putting on the lawn surrounding it. And I did cut it down quite a bit a few years ago to lower and refresh it. Is there anything I can do to get strong new growth going again? I use it for privacy and right now there is very little. Thank you for your help with this.
— Chuck Graves, Center Valley
Privet is one of those plants that can divide gardeners into two camps. Some love the evergreen leaves coloring the winter landscape, providing the base for beautiful formal topiaries and hedges. Others see it as an invasive, non-native intruder. The very same qualities — hardiness, ease of growth, resistance to disease and endurance, make it easy to love and an intrusive bully.
While there are plenty of varieties of privet (Ligustrum spp.) in the world, in our area most plants are one of four.
This shrub has petite green leaves, leathery and arranged alternately on the stem, and delicate, fragrant, white tubular flowers in the late spring. Privet grows 4 to 15 feet tall, four to 10 feet wide, depending on the variety. While it grows best in full sun, this shrub does well in partial sun as well and is not picky about soil — as long as the pH is around neutral (6 to 7) and well-drained.
Shrubs are planted about a foot apart individually or in two-foot-wide trenches in holes about two feet wide. One admirable quality is that privet has some limited tolerance for salt, making it a good selection for growing along driveways and streets.
Fertilize with 15-5-10 in the early spring, after the new growth leafs out, and fall. Prune after flowering and trim as needed to retain shape throughout the growing season. Control spread by hand pulling small plants regularly.
Now to address Chuck’s situation. Privet is very hardy and long-lived but does have several problems that can damage or kill even the best-treated hedge. If the change is sudden, check first for pests, signs of disease and alternations to the available light or water drainage.
A common culprit is anthracnose, twig blight or honey fungus. Anthracnose, a fungal disease, attacks new shoots and appears as dieback and brownish spots on the leaves that eventually spread over the entire leaf. This and some other fungal diseases are soil-borne, attacking the roots of the plant and causing a slow death over several years. Treat by removing and destroying all foliage and wood that is diseased. Keep the leaf debris cleared from under the shrubs. Also, thin out the shrubs when dormant to improve the air circulation.
If you are considering planting privet, select an anthracnose-resistance privet such as amur (L. amurese), California (L. ovalifolium Hassk), ibota (L. obtusifolium), or regal (L. “Regelianum”).
Another suspect is root rot. Although privet is very tolerant of heat and drought, they are sensitive to root rot if the soil is wet or heavy.
If you see mushrooms at the base of the plant, suspect armillaria root rot (oak root rot, Armillaria melea). If the branches and twigs are covered with white spores, research Dematophora root rot (Dematohora or Rosellinia necatrix). Control either by controlling irrigation, limited watering and improving soil drainage. The ideal control is to remove infected plants, especially roots, and remember to destroy and dispose of the problem plants.
A problem caused by extensive or improper pruning can also cause hedges to thin. Chuck correctly noted that his hedge is cut so that the top is narrower than the bottom. This avoids restricting the sunlight on the lower limbs, a common problem with many types of hedges.
However, shearing can be troublesome. It does make a compact shrub but it also makes the branches form at the surface and create a dense mass of branches and twigs. These surface branches can be damaged by sudden cold snaps, drying in cold windy weather and drought conditions. Damage can extend into the shrub creating that open look Chuck is experiencing. Treat twig kill by trying more targeted hand trimming and patience to encourage new branching.
There are some pests that are attracted to privet. Scales — black California red, and pit scales, to mention a few. Black vine weevil, ash borer, lilac borer, blister, gall, and rust mite can also be a problem. However, the hardy privet is rarely seriously damaged by insects.
Suggested alternatives for privet are flowering dogwood (Cornus Florida) and black haw (Viburnum)