Good old fashioned boxwood hedges really look silly if just a single missing plant get replaced with a different cultivar (cultivated variety) or specie. Most of the older boxwood hedges are the traditional, but somewhat yellowish Japanese boxwood. Most middle aged hedges are a relatively newer cultivar that is a bit greener. Modern boxwood hedges are more likely a cultivar of English boxwood, Buxus sempervirens.
English boxwood resembles Japanese boxwood, but has slightly narrower leaves that produce a slightly more objectionable aroma when shorn or otherwise disturbed. These opposite (paired) glossy leaves are only about a quarter to half an inch wide and about twice as long. The color is slightly darker with a more ‘olive’ tone. Wild English boxwood in Europe can grow as small trees. Most garden varieties are fortunately much shorter and more compact, which is why they are so popularly shorn into small formal hedges. They also do well as topiary. ‘Aureo Variegata’ is variegated with nicely contrasting cream colored leaf margins.
It is difficult to know how big any of the various cultivars of English yew,Taxus baccata, will eventually get, and how long they will take to get that big. Most can get almost as tall as thirty feet. Some can get nearly twice as tall. However, they can take more than a century or several centuries to do so. Old specimens around Europe are significantly older than two thousand years. Slow growth is an advantage for formal hedges that get shorn only annually. English yew prefers regular watering. Partial shade is not a problem.
Irish yew is actually a cultivar of English yew with densely upright growth. The various golden yews have yellowish foliage. Otherwise, most English yews have finely textured dark green foliage on angular stems that resemble those of redwood. Individual leaves are very narrow, and only about half and inch to an inch long. The peeling dark brown bark resembles that of large junipers, but not quite as shaggy. English yew is toxic.
With indiscriminate pruning, glossy abelia, Abelia X grandiflora, will never develop its natural form, with elegantly long and thin stems that arch gracefully outward. Sadly, almost all get shorn into tight shrubbery or hedges that rarely bloom. If only old stems get selectively pruned out as they get replaced by fresh new stems, mature shrubs can get eight feet tall and twelve feet wide.
Against their bronzy green foliage, the tiny pale pink flowers that bloom all summer have a rustic appeal. In abundance, they can be slightly fragrant. The tiny leaves are not much more than an inch long. Vigorous young canes that shoot nearly straight out from the roots slowly bend from the weight of their bloom and foliage as they mature.
Partial shade is not a problem for glossy abelia, but will inhibit bloom somewhat. Young plants want to be watered regularly. Old plants are not nearly so demanding, and can survive with notably less water. If alternating canes is too much work to restore old and neglected plants, all stems can be cut back to the ground at the end of winter. New growth develops quickly.
Heavenly bamboo, or simply ‘nandina’, is one of those many plants that almost never performs like it should. The intricately lacy foliage is so appealing while plants are young, and changes color with the seasons. The red berries can be comparable to those of holly. Unfortunately, healthy plants grow, and then ultimately get shorn into globs of disfigured leaves and stems.
The same abuse afflicts Oregon grape (mahonia), mock orange (philadelphus), forsythia, lilac, abelia and all sorts of shrubby plants that really should be pruned with more discretion. Their deteriorating older stems should be pruned to the ground as new stems grow up from the roots to replace them. It is actually not as complicated as it seems.
This pruning process, known as ‘alternating canes’, prunes the plants from below. It is a standard pruning technique for maximizing production of blackberries, raspberries and elderberries. It is similar to grooming old stalks from bamboo and giant reed, even if it does not prevent them from spreading laterally.
The deteriorating older stems, or ‘canes’, are easy to distinguish from newer growth. Old canes of Heavenly bamboo and Oregon grape become heavy on top, and flop away from the rest of the foliage. Old canes of mock orange and lilac get gnarled and less prolific with bloom. Aging abelia and forsythia canes become thickets of crowded twigs.
The newer stems are likely a bit lower, but are not so overgrown. Since the foliage is not so crowded, it is displayed on the stems better. Their blooms or berries are more abundant. By the time new growth becomes old growth, there will be more newer growth right below it. In fact, the regular removal of aging canes stimulates growth of new canes.
This is the time to prune Heavenly bamboo and Oregon grape, just because the oldest foliage is as bad as it will get after the warmth of summer. Mock orange, forsythia and lilac should get pruned while dormant through winter, but are commonly pruned just after they finish bloom early in spring. Abelia should probably wait until spring because new growth can look sad through winter.
Port Orford cedar is a grand tree. It is native to the southern coast of Oregon and the very northwestern corner of California. Mature trees in the wild are more than a hundred fifty feet tall. Some of the older big trees within landscapes are more than forty feet tall. However, the cultivar known as bird nest cypress, Chamaecyparis lawsoniana ‘Nidiformis’ is remarkably diminutive and shrubby.
Bird nest cypress grows slowly, and may never get more than five feet high and wide. Individual plants are mounding with rather flat tops. A row of plants eventually becomes a low informal hedge. Distinctively flat sprays of slightly grayish evergreen foliage exhibit a soft feathery texture. Unless pruned otherwise, abundant dense foliage obscures main limbs with fissured reddish brown bark.
Most cultivars of Port Orford Cedar, including bird nest cypress, are uncommon here. They actually prefer cooler and moister climates. Locally, they are sensitive to harsh exposure and wind while the weather is warm. A bit of partial shade is no problem. Established plants do not need much water, but should not get too dry for too long. Selective pruning, not shearing, sustains natural form.
As a backdrop for more interesting plants, shiny xylosma, Xylosma congestum, may not get the respect that it deserves. If it seems to be a bit too common in some big landscapes, it is probably because it is so practical. It can function like the strictly shorn hedges that were popular decades earlier, but is a bit more adaptable to modern landscape styles. It can be formal or quite informal.
Formal hedges of shiny xylosma are typically no taller than eight feet, and a bit more plump than old fashioned privet hedges. They can get a bit sparse if kept too lean. Informal hedges are mostly lower and plumper, with casually irregular surfaces and no corners. Old shiny xylosma can grow as a small tree more than eight feet tall. Younger specimens are of the shorter cultivar, ‘Compacta’.
Established shiny xylosma is surprisingly resilient. Roots disperse impressive distances to reach moisture so that old specimens can survive without direct irrigation. Although, they prefer regular watering. Overgrown specimens can eventually regenerate nicely from coppicing or pollarding. The main disadvantage is that vigorous new growth will likely develop concealed but sharp thorns.
Here on the West Coast of California, Indian hawthorn, Raphiolepis indica, was formerly popular as a foundation plant. The compact hollies that were used as such in the East never became very popular here. Back when rain gutters were prohibitively expensive, foundation plants diffused water as it fell from roofs. This limited erosion, and also inhibited splattering onto lower parts of walls.
Modern Indian hawthorn cultivars are now appreciated elsewhere in landscapes for profuse pink bloom in late winter or early spring. Sporadic bloom might continue through summer, with a minor secondary bloom phase in autumn. The most compact cultivars display slightly richer pink bloom, followed by mildly bronzed new foliage. At least one cultivar exhibits barely blushed white bloom.
‘Majestic Beauty’ is a cultivar that might be a hybrid with loquat. It can grow as a small tree more than ten feet high and wide. Other cultivars do not get half as big. Most get less than four feet high. They work nicely as low and plump hedges, but should be shorn after bloom. Full sun exposure and occasional irrigation should be sufficient. They are popular, because they are so undemanding.
Of all the popular pittosporums in Western landscapes nowadays, the karo, Pittosporum crassifolium, is certainly not one of the most familiar. It might have been one of the earliest to have been popularized here though. Because of its resiliency to coastal climates, it was a common hedge in San Francisco during the Victorian Period. With minimal watering, it did well farther inland too.
Karo are nice fluffy evergreen shrubs that can get fifteen feet tall. They excel both as informal screens and refined hedges, and can be staked as small trees on single straight trunks. Alternatively, lower growth of big shrubby specimens can be pruned up to expose a few delightfully sculptural trunks. ‘Compactum’ is a densely foliated mounding cultivar that might stay less than three feet tall.
The Latin name, Pittosporum crassifolium, is quite descriptive. The literal translation is “sticky-seed thick-leaf”. The two or three inch long leaves are not really thick, but their slightly grayish upper surfaces and more grayish tomentous (fuzzy) undersides make them seem almost succulent. Small and round seed pods eventually split open to reveal dark seed glued together with sticky resin.
Ah, something vintage! Remember Hollywood juniper, Juniperus chinensis ‘Kaizuka’ (or ‘Torulosa’) flanking big two-car garage doors of mid century modern homes? Those that are still around after half a century are big and strikingly sculptural, like miniature Monterey cypress for home gardens. They get about fifteen feet tall and ten feet wide, but have potential to get significantly larger.
Hollywood juniper is an old classic that is still reasonably available in some nurseries. Their densely foliated stems twist and turn picturesquely upward, typically leaning one way or another toward sunlight or away from prevailing wind. Some say they look like frozen green flames. Their gnarly trunks and flaking bark can be exposed as they grow tall enough for low growth to be pruned away.
Because of their very irregular branch structure, Hollywood juniper is more adaptable to free-formed pruning than the presently trendy junipers with strictly upright or conical form. They must never be shorn, but do not mind if obtrusive limbs get pruned back to the main trunks. Therefore, they are actually more adaptable to smaller modern gardens than some modern cultivars of juniper are.
A surplus of common names seems to be a common theme for many plants that we thought we knew the names of. The simple Pittosporum tobira, which might be known here by its Latin name, might instead be known as mock orange, Australian laurel, Japanese pittosporum, and Japanese cheesewood. Its native range is about as diverse, including Greece, Japan, Korea and China.
Back in the 1990s, the compact cultivar known as ‘Wheeler’s Dwarf’ was common enough to be as cliché as tam junipers were in the 1950s. There are actually a few other dwarf and variegated cultivars that do not share that reputation. Most are low, dense and mounding. ‘Variegata’, although not a compact dwarf, grows slower and stays smaller than the unvariegated straight species.
Otherwise, Pittosporum tobira gets about ten feet tall and wide. It can eventually get significantly taller, especially if lower growth is pruned away to expose the sculptural trunks within. If shorn as a hedge, it should not be shorn so frequently that the dense foliage is always tattered. Leaves are delightfully glossy and convex. Small trusses of modest pale white flowers are sometimes fragrant.