Strictly formal boxwood hedges are traditional components of old formal rose gardens. In California, Japanese boxwood, Buxus microphylla, had always been more popular than English boxwood, which may be more common where winter is cooler. Although it grows too slowly for high hedges, it gets high enough to obscure gnarled lower growth of roses.
Mature plants are generally less than three feet tall and wide, although they can get a bit larger if they get a chance. The oval and glossy evergreen leaves are only about half an inch or an inch long, but relatively thick, so are very conducive to formal shearing. Foliar texture is nicely dense but not too congested. Gray or pale brown bark is seldom visible.
Old fashioned Japanese boxwood, which remains the most common in old gardens, has a somewhat light or yellowish green color. Modern cultivars are darker green. A common problem with old formal hedges is the addition of modern cultivars or even other species to fill gaps. The darker foliage will not conform to the lighter foliage, so ruins the formality.
Large shorn hedges or informal screens are the more popular functions of Pittosporum eugenioides. It works like a modern and more relaxed option to privet. What few garden enthusiasts know is that it can alternatively be allowed grow into a small tree, either as a standard (on a single trunk) or with multiple trunks. It grows rather efficiently to more than twenty feet tall and about half as broad while young, and as it matures, can eventually get about thirty feet tall and broad.
The glossy leaves have appealingly wavy margins and distinctively pale midribs. The slightly fragrant flowers are only pale yellow, and are not abundant among young trees. Big old trees often bloom enough in autumn to be pleasantly fragrant. Stems and foliage are lemony fragrant when pruned or shorn. However, the common name of ‘lemonwood’ (or tarata) is not so common locally for Pittosporum eugenioides.
Foliage is often employed to obscure views. Evergreen shrubbery or trees can provide privacy in the garden or for windows. It can just as easily hide unappealing buildings in the distance, or driveways where cars get parked. Unfortunately, too much foliage often obscures desirable views or interferes with lighting.
There are all sorts of reasons to control greenery that might otherwise get overgrown. Overgrown shrubbery and trees not only hides the architectural appeal of a home, but can also be a security risk by concealing windows and doors that burglars might break into, and by obscuring security lighting and street lights. Too much shade prevents lower plants from getting the sunlight they need.
The best way to limit overgrowth is by selecting plants that stay proportionate to their intended functions. For example, shrubbery below windows should naturally stay lower than the lower windowsills. Shade trees for areas where views should stay open should have high branch structure and relatively bare trunks. Well, most of know that this does not always happen.
The options are limited for greenery that wants to get larger than it should. Obviously, it can be pruned regularly; but this may be more work than it is worth, and can cause disfigurement Some plants can be pruned less frequently if pruned more severely, but will be bare and potentially unsightly for quite a bit of time. Overgrown plants can alternatively be removed and replaced with plants that are more proportionate to intended functions.
An option that is not often considered is an ‘updo’. Trees and large shrubbery that are obtrusive to views or lighting can be pruned up and over what they are being obtrusive to. For example, lower growth of large pittosporums that is covering low windows can be pruned away to expose bare inner trunks supporting higher growth. The lower trunks can be appealingly sculptural without being too concealing. This works nicely for large shrubbery like viburnum, bottlebrush, oleander, photinia and pineapple guava.
Street trees that interfere with street lights (or marquis on storefronts) may need to be updo pruned a few times for adequate clearance, but these procedures are much less work, are less disfiguring to the affected trees, and produce more appealing results than keeping trees down.
Johnny jump up and jumping cholla have no more than amusing names in common with hopbush, Dodonea viscosa. Neither a dangerous cactus nor a docile annual, hopbush is an elegantly upright and evergreen shrub. It is very popular for both informal and formally shorn hedging. With pruning, it can become a small tree with handsomely furrowed bark.
Hopbush has potential to get about as tall as a two story house, particularly with pruning for tree form. Conversely, with only occasional pruning for hedge form, it is just as happy to stay just six feet tall. Trees with single and straight trunks fit nicely into narrow spaces. Trees with a few irregular trunks that lean outwardly are more sculptural for larger areas.
The narrow evergreen leaves are about two or three inches long, with light bronzy color. ‘Purpurea’ has purplish bronze color, but does not grow as vigorously. Most hopbush are female, and generate interestingly papery seed. Bloom and seed production are variable though, and some specimens become male. Roots should be complaisant with concrete.
Of the several junipers that were too common decades ago, the golden pfitzer juniper, Juniperus X pfitzeriana ‘Area’, was the one outfitted with cheery, bright yellow new foliage each spring. Similar but more compact varieties that are more popular now were rare back then, or simply not yet invented. Contrary to the stigma, golden pfitzer juniper is a very tough shrub, which is why so many from decades ago remain in older gardens, and new plants can sometimes be found in nurseries. Once established, they need very little water, or none at all. A bit of partial shade is tolerable, but inhibits color. Angular branches radiate outward, with the finely textured foliage drooping only slightly at the tips. Mature plants get wider than six feet, and taller than four feet. Crowded plants can stand taller than six feet. Golden pfitzer juniper can technically be shorn as hedges, but are so much more appealing if selectively pruned to maintain their natural form. They are at their best where they have space to spread out naturally without pruning.
Almost all photinia in local landscapes is Fraser’s photinia, Photinia X fraseri, which is a thornless and fruitless hybrid of two species that are now rare. Some of the old fashioned photinia are thorny. Some produce copious berries that can get messy, or feed birds who can get messy. More modern cultivars of Fraser’s photinia are becoming more available.
Fraser’s photinia is popular as a shorn evergreen hedge. New foliage that develops after shearing is richly reddish bronze, and fades to dark green. Bronze color is best in spring, after late winter shearing. Summer shearing stimulates a repeat performance, although it may not last as long before the foliage fades to green. Shearing enhances foliar density.
Unshorn photinia can develop into small trees as tall as fifteen feet, with new growth that is a bit less richly colored than that of shorn photinia. It also blooms, often profusely, with big and rounded trusses of tiny creamy white flowers. Bloom is not impressively colorful. Floral fragrance is objectionable to some. All photinia types are susceptible to fire blight.
Where it had been left to develop naturally in old freeway landscapes, shiny xylosma, Xylosma congestum, grew as small trees. The largest are significantly taller than twenty feet. They can be pruned up to expose their nicely flaking bark on sculptural trunks and stems. The evergreen foliage is shiny and rather yellowish green, somewhat like that of camphor tree. The slightly serrate leaves are about two inches long or a bit longer. The tiny and potentially fragrant flowers are rarely seen, and not worth looking for. In refined landscapes, shiny xylosma is popular as a shorn hedge. Xylosma congestum ‘Compacta’ has denser growth, and can be kept only a few feet high if necessary. Vigorous shoots can have nasty thorns hidden in their deceptively gentle foliage. Once established, shiny xylosma does not need much water. It prefers full sun exposure, but will tolerate a bit of shade.
All the wrong plants get shorn. Mow, blow and go gardeners are known for shearing everything that they can reach into creepy and unnaturally geometric shapes, usually flared out at the top, and bulging obtrusively into otherwise usable space. Yet, functional formally shorn hedges are passe and almost never shorn properly.
First of all, a formal hedge should be uniform, which means that all the plants that comprise it should be the same, and planted at the same distance from each other. Any plants within a formal hedge that die should be replaced with the same plant. A single English boxwood plant added to a Japanese boxwood hedge will always stand out with a different shade of green and growth pattern. Seedlings of other plants that grow up into a hedge should be removed before they become part of it.
Secondly, a formal hedge should be contained within defined boundaries. It should get neither too tall, nor too deep (from front to back). A fat hedge wastes space. There is no excuse for a hedge to encroach obtrusively over walkways, driveways or patios.
The vertical faces of a hedge should be completely vertical or slope very slightly inward at the top, but should certainly not slope outward to shade lower growth. A slight inward slope is more important on a northern face of plants that are sensitive to shade.
Hand pruning hedges (with hand shears) produces the best finish, but takes quite a bit of time for big hedges. Shearing with typical hedge shears cuts leaves as well as stems, so can cause foliage with large leaves to look a bit tattered for a while. Hedges that grow fast may need to be shorn twice or more annually. Some hedges can get shorn back aggressively once annually, and then allowed to fluff out evenly through the rest of the year. Bottlebrush and escallonia hedges can bloom nicely and evenly if shorn only once annually.
Glossy and wax leaf privet are among the most traditional of formal hedges. Glossy privet can get quite tall, but wax leaf privet actually has glossier foliage. Photinia and shiny xylosma have a bit more color, but want a bit more space (from front to back). Boxwoods make very nice small hedges. Pittosporums are available in various shapes and sizes. Pittosporum eugenioides gets quite tall, and can be kept quite lean. Pittosporum tobira is shorter and wider.
There are too many other plants known as ‘mock orange’ for Pittosporum tobira to still go by that name, which is why it is more commonly known by its Latin name, or simply as ‘tobira’. The pleasantly fragrant flowers do not smell too much like those of orange anyway. The glossy and dark green leaves are like those of some hollies, without the distinctive prickly points. ‘Variegata’ has lighter green foliage variegated with white, but does not bloom as much. Dwarf cultivars, both variegated and unvariegatd, bloom even less. ‘Variegata’ has a tendency to occasionally produce stems of green (unvariegated) foliage that grow more vigorously and can overwhelm the original variegated growth if not pruned out. Common green Pittosporum tobira can grow as a small tree in the partial shade of larger trees, but is more often maintained as dense shrubbery less than ten feet tall. It makes a nice dense hedge in full sun, but unfortunately does not bloom if shorn regularly. All cultivars are resilient to drought once established.
Too much of a good thing eventually gets old. That is how so many of the good junipers that were so popular half a century ago became so unpopular. They became too common, and many were planted into situations that they were not appropriate for. As they matured, many became overgrown or disfigured. Only recently have a few newly introduced modern cultivars restored the appeal of both new and traditional junipers to a generation that is less familiar with their former stigma.
Even though all junipers are evergreen and somewhat similar in regard to foliar texture and their lack of interesting bloom, they demonstrate considerable diversity. Some are low and sprawling ground covers. Others are dense low shrubbery. A few develop as small trees. Branch structure may be densely compact, gracefully arching, rigidly upright, or sculpturally irregular.
Some junipers have yellowish new growth that eventually turns to a more typical deep green. Others are bluish gray throughout. A few rare types are variegated. Almost all junipers have scale-like leaves (like those of cypress). A few have needle-like leaves.
‘Blue Arrow’ and more traditional ‘Skyrocket’ junipers are like short and plump Italian cypress with bluish or gray foliage. ‘Wichita Blue’ juniper is even shorter and plumper, with more sculptural branch structure. However, it is not nearly as irregular and sculptural as the old fashioned ‘Hollywood’ juniper. Modern ‘Gold Star’ and the older ‘Old Gold’ junipers are shrubby types that exhibit arching stems with gold tips.
‘Icee Blue’ is like an improved version of the classic ‘Blue Rug’ juniper, that matures as a shallow bluish ground cover. ‘Blueberry Delight’ juniper is one of the few junipers known for conspicuous fruit, with pretty powdery blue berries against grayish needle-like foliage on trailing stems. ‘Limeglow’ juniper gets a bit deeper, and exhibits chartreuse new growth that turns rich green.
Just because junipers can be shorn certainly does not mean that they should be! Shearing deprives junipers of their naturally appealing texture and form. Instead, junipers should be selectively pruned only where necessary to eliminate growth that is beginning to become obtrusive. Stems should be cut back deeply into the main stems from which they originate, in order to avoid leaving stubs or disfigured stems. Tree junipers like ‘Hollywood’ juniper, as well as overgrown shrubby junipers, can be pruned to expose bare trunks and stems. The gnarly stems and shredding bark can be as appealing as the foliage that obscures them.
Otherwise, once established, junipers do not need much attention or water, and are remarkably resilient. They only rarely get infested with spider mites or scale insects, or get damaged by disease. They only want good sun exposure.