Above, Privet hedge at Huntington Library, San Marino California
Ligustrum japonicum, or the shorter selection L. japonicum 'Texanum', is the species of Privet typically used in southern California--in other regions the common name "Privet" refers to a different Ligustrum, such as L. vulgare or L. amurense.
Tall, narrow hedges are becoming ever more popular in southern California as lot sizes shrink and the region becomes more crowded. It seems as though the more people there are, the more we all desire privacy.
Professional growers have recently developed a technique for growing Ligustrum japonicum as tall, narrow, and fast as possible. Other plants, most famously several species of Ficus, have become notorious for aggressive, pavement-cracking root systems and have thankfully lost favor as hedging plants. Syzygium (Eugenia) for decades the go-to plant for hedging, is still struggling to recover favor after the Eugenia psyllid devastated so many plants a decade or two ago. Ligustrum is much less bothered by pests, and its root system is far less aggressive than Ficus.
I first saw this Ligustrum growing method at the Huntington a few years ago, when they installed some Ligustrum hedges as part of remodels. I saw the hedges, noting how dense yet how narrow they were, then during a grow house visit, saw how the immature plants are trained to grow that dense yet that narrow.
The new growth of Ligustrum japonicum is naturally long, flexible whippy stems when sufficiently watered and encouraged with fertilizer. Growers use this behavior to to create exactly what nearly everyone in So Cal seems to want: tall, fast, cheap privacy.
The method is to tie those long whips vertically to a tall stake until the whips mature and harden up. At that point, they will remain vertical after the stakes are removed. The result is a hedge that grows taller, narrower, denser and faster than leaving the shrub to develop naturally.
There's a wooden stake under that:
The whips branch out fairly quickly, producing plants like this:
This allows landscapers to install a near instant tall privacy screen. The 15 gallon container sized plants above were over 8' tall. L. japonicum's natural height is anywhere from two to six meters (6.5' to 20'). Hedge height is ultimately restricted to the height of the maintainer's ladder and reach.
Across the street from the above new hedge, is an older example that probably inspired the planting of the new one. Within a year or two, developed with several light shearings of side growth branching off the main vertical stems, the hedge becomes a dense privacy screen:
This hedge is about eight feet tall but only about 30" wide.
Incidentally, I've blogged about this particular property before. The garden began with a whole lot of Agave vilmoriniana, which bloomed all at once within three years of planting. I took a peek behind the hedge--the Agaves have been replaced with other succulent plants, and the garden still looks good. There are still a couple of Agaves, but they have bloomed also. The residents switched to non-monocarpic Aloes.
For non-gardeners, a fast, cheap, effective screen like this has high appeal. The even, rich green provides visual rest in the way that a lawn does, and Ligustrum has fairly low water requirements. A plant afficianado may prefer a more exotic, unusual, or varied hedge--but a plain, dark green, tough, useful background plant cannot be easily dismissed.