Not many arborists or horticulturists are fond of the unremarkable but very popular London plane tree, Platanus X acerifolia. It soon gets too large for many of the tight situations it gets planted in, more than thirty feet broad and more than forty feet tall. Although it is among the most common of street trees, it can produce aggressive buttressed roots that displace sidewalks and curbs. Fuzz (tomentum) from the leaves is irritating to the skin or if inhaled.
Older trees that were planted prior to the development of disease resistant varieties are very susceptible to anthracnose and mildew, and are likely to infect other susceptible plants. Infected trees often get their foliage late in spring (after earlier new foliage shrivels and falls), or defoliate by late summer. Otherwise, the slightly raspy eight inch wide leaves seem sickly as they turn grungy yellowish brown in autumn.
Landscapers use London plane trees too commonly merely because they are so reliable. They tolerate most soils, smog, severe exposure (such as reflected glare from pavement) and a bit too much watering. Modern varieties are not quite as susceptible to disease. ‘Yarwood’ has large rounded leaves that are resistant to mildew. ‘Bloodgood’ is less susceptible to anthracnose. ‘Columbia’ is less susceptible to both diseases.
Large limbs and trunks with mottled gray and tan bark are rather sculptural while bare through winter. London plane happens to be conducive to annual pollarding, which makes the limbs even more sculpturally gnarly, and produces more vigorous growth with larger leaves that are less susceptible to disease.
Trees are the most significant components of the landscapes that they inhabit. They get larger than all other plants, and live for decades or centuries. Because inappropriate trees have such potential to cause such serious problems, and can be so difficult and expensive to remove, it is important to select trees that are appropriate to each particular application.
Size and form of trees when they mature are important considerations. Crape myrtles are small to midsized trees that fit nicely into tight spots, but are too dinky to be good street trees. London plane trees are more proportionate as street trees, but eventually displace sidewalks and curbs with their aggressive buttressed roots. Chinese elms can be good street trees, but need to be pruned regularly to maintain clearance. Red maples are a better choice because they get large enough without getting too big, have complaisant roots, and are easily pruned for adequate clearance.
Other features in the area can limit tree selection. Poplars and willows have aggressive roots that invade septic systems or old unsealed iron or terra cotta sewer pipes. Queen palms eventually reach utility cables, but can not be pruned to go around them. Any good shade tree can provide too much shade over solar panels. Partial shade from large trees or structures is a problem for most other trees, but is actually preferred by a few ‘understory’ trees like vine maples, Japanese maples and dogwoods.
Trees that are expected to provide shade through summer should probably be deciduous, like red oaks or silk trees, to allow warming sunlight through during winter, particularly close to the home. However, trees that should obscure unwanted views should be evergreen, like Southern magnolias or arborvitaes.
Some trees that need more attention than others are only appropriate where they will get the attention they need. Mexican fan palms are easy to care for while young, but eventually grow out of reach and need to be groomed by professional arborists. Of course, every tree is limited to particular climates. Various ficus trees that are common in nurseries in San Diego will not survive even a mild frost, which is why they are not available in San Jose.
Actually, this does not even qualify as pollarding. It looks as if this tree, which was one of a few similarly damaged Acacia melanoxylon, black acacia trees, was in the process of being removed when the crew who was removing it left for the day. It would not have been so bad if they had returned to remove it and the others completely. They did not. This was the finished product. It and the others were almost twenty feet tall in this condition. They were about twice as tall prior. This sort of hack job is what gives pollarding a very bad reputation. It also demonstrates why proper pollarding should not be so vilified that arborists do not learn how to do it. Very obviously, this is not proper. Because they could not be salvaged, all of these trees were cut down a few days after I got this picture.
Pollarding can be done for a variety of reasons, and has been done for centuries in various cultures. It is still respected technique in many or most cultures. It stimulates vigorous growth that can be fodder for some types of livestock, including silkworms who consume the vigorous foliage of pollarded white mulberry trees. It can prevent some trees from producing troublesome pollen or fruit, such as old orchard olive trees that were retained as homes and their respective gardens were constructed around them. It can enhance autumn foliar color for some types of deciduous trees, such as the old Schwedler maples that were formerly common as street trees in San Jose. It stimulates growth of vigorous cane stems that are useful for basketry, fences, trellises or kindling. Locally though, it is considered to be as egregious as the technique pictured above, which is why no one here learns about it.
Grecian bay is, as its name suggests, endemic to Greece and the Mediterranean region. California bay, Umbellularia californica, is native to California and southwestern Oregon. The two are very different. Although California bay can be useful for culinary application, it is twice as pungent. For replacing Grecian bay in recipes, half as much should suffice.
California bay also grows much larger and more irregularly than Grecian bay. With good sun exposure, it grows more than forty feet tall. Where it competes for sunlight in forests, it can grow a hundred feet tall. Domestic trees typically develop on single vertical trunks. Wild trees might develop several leaning trunks. Foliar canopies are densely evergreen.
California bay is uncommon within urban home gardens because it is so big and messy. It is more likely to inhabit rural gardens either by self sowing or by being there first. Some old trees that grew from stumps of older trees can develop basal decay. Stumps might be difficult to kill. Foliar and floral detritus inhibits smaller vegetation and seed germination. Some abhor the foliar aroma.
Horticulture is as diversified as horticultural professionals. Nurserymen grow horticultural commodities. Landscape designers plan installation of the commodities into landscapes. Landscapers construct the landscapes. Gardeners maintain them afterward. Florists use floral commodities. Arborists specialize in arboriculture, which is the horticulture of trees.
Arboriculture is necessary because trees are so substantial. Although most arborists can work with smaller trees, larger trees are their priority. Other horticultural professionals are neither qualified nor able to work with such trees. Similarly, arborists are too specialized to engage with landscape design or floristry. Arboriculture is truly an intensive discipline.
Many garden enthusiasts maintain their own trees while such trees are somewhat small. Some trees, such as dwarf citrus and Japanese maples, stay small. However, most trees eventually grow beyond reach from the ground. Even within gardens that lack gardeners, arborists might become necessary. This is certainly not something to be negligent about.
When pansies get tired in spring, gardeners can replace them with petunias for summer. Trees are completely different. They are the most substantial and persistent vegetation in their respective landscapes. Some can survive for a few centuries. The consequences of their neglect can be disastrous. Arboriculture is crucial to the safety of their environment.
The importance of arboriculture typically becomes more apparent during wintry weather. Rain destabilizes roots. Wind weakens the integrity of limbs and trunks. Generally, trees become messier and more hazardous than at other times of year. However, arboriculture is a concern throughout the year. Spontaneous limb failure is more likely during summer.
Besides, several procedures for certain trees are more appropriate during other seasons. Furthermore, mitigation of potential problems is easier before they become emergencies. Information about arboriculture is available from the International Society of Arboriculture or ISA. Their website, which also provides a list of certified arborists, is at isa-arbor.com.
Citrus trees are not like deciduous fruit trees. They are not marketable as bare root stock. They do not need winter pruning. Actually, winter pruning might initiate premature growth that is vulnerable to frost. Deciduous fruit trees remain dormant so can only dream about fruiting for next summer. Citrus trees are happily evergreen, and fruiting abundantly now.
Citrus somehow seem to be more summery than fruit that actually ripen for summer. Iced lemonade is so traditional for warm summer weather. Oranges for Christmas might seem to be out of season when they really are not. Although Mandarin oranges are perishable, other ripe citrus last for weeks or months. Several ripen sporadically throughout the year.
‘Valencia’ oranges, which are the traditional juicing oranges, might last through summer. They may sustain the belief that orange juice is a summery beverage. Several grapefruit cultivars can last about as long. ‘Eureka’ lemon is mostly seasonal, but also generates a few fruits throughout the year. ‘Bearss’ lime may be even more productive out of season.
With only one exception, all species and cultivars of citrus are of the same Citrus genus. Kumquats are of the Fortunella genus, but typically qualify as Citrus for simplicity. Citrus fruit is sweet, sour or bitter. Most familiar oranges are sweet. ‘Seville’ is a sour orange for marmalade. ‘Bouquet de Fleur’ is a bitter orange for infusing with Grand Marnier cognac.
Oranges, lemons, limes, grapefruits, kumquats and Mandarins are all very familiar. All of these fruits are available from grocery markets. Their trees grow in many home gardens. Tangerines are simply Mandarins or Mandarin oranges of the Americas. Pomelos, which are larger ancestors of grapefruits, are still uncommon. So are tiny and tart calamondins.
They are not the most unusual, though. Blood oranges provide tangy red juice. ‘Rangpur’ lime is a sour Mandarin orange that is as acidic as a ‘Eureka’ lemon. Tangelos combines the tartness of grapefruits with the sweetness of Mandarin oranges. Sweet limes lack the acidity of typical limes, so are for eating like oranges. These are merely a few examples.
There should be no stigma associated with cut Christmas trees. They grow on farms, not within natural ecosystems, as some believe. Like cut foliage, cut flowers and vegetables, they are an agricultural commodity. They generate no more greenwaste than an average lawn. Yet, potted Christmas trees are popular as an ‘environmentally responsible’ option.
Potted Christmas trees, however, can be more of an environmental detriment. Only those that perform for a few years consume less resources than cut Christmas trees. Almost all deteriorate too much during their first summer for a second Christmas. Therefore, they do not perform any more perpetually than cut trees. They are, however, costlier and smaller.
The expense of potted Christmas trees is proportionate to the resources which they use. Proportionately, they require more fertilizers, pesticides and infrastructure than cut trees. This is also relevant environmentally. So is their synthetic growing medium, plastic pots, and for some, mylar wrapping. Transportation is more efficient only for the smallest sorts.
Regardless, for many households, potted Christmas trees remain after Christmas. Some of the most expensive sorts are fortunately more likely to be practical sorts. They may be compact types that are conducive to confinement within big pots. If so, they may function as Christmas trees for a few years. Afterward, they might fit nicely into their home garden.
This includes a few cultivars of spruce as well as fir and even pine. Dwarf Alberta spruce is easy to accommodate in both pots and gardens. Large specimens are expensive and rare though, so few need accommodation now. Blue spruce is more practical as a potted Christmas tree, but grows larger. Eastern redcedar can stay in a large pot for a few years.
The most common potted Christmas trees are Italian stone pine and Canary Island pine. These are the small sorts with cheap ornaments and mylar wrapping. They too often lack identification or description of how large they grow. Consequently, those who plant them too often provide inadequate space. Such big trees can be very destructive as they grow.
Some live Christmas trees grow too big for home gardens.
They appear to be so simple and innocent now, shorn strictly into conical form and perhaps adorned with any remnants of their Christmas time employment, but living Christmas trees can potentially become big problems. Italian stone pine, which is one of the most popular living Christmas trees, can get nearly eighty feet tall and sixty feet wide, with massive trunks and limbs! Regardless, they often get planted in small gardens and tight situations after Christmas because they do not seem like they would do any harm.
Most living Christmas trees can eventually become large trees. Canary Island pine, Aleppo pine, Monterey pine and Afghan pine are the most notorious since they are the most common, and also because they are not so easily recognized while they are young Christmas trees. Their juvenile foliage is more softly textured and often lighter colored than their more substantial adult foliage.
These most common living Christmas trees do not like to stay potted for very long, and are not very conducive to subsequent shearing. Consequently, many do not survive through their first summer, and those that do often get planted in the garden without much thought. Until recent years, they were seldom labeled; so few people knew how big they could get.
Coastal redwood, giant redwood, deodar cedar and Arizona cypress as living Christmas trees are neither as common, nor as likely to not get recognized as trees that eventually get quite large. They need their space nonetheless. Fortunately, they are generally somewhat more practical for some spacious gardens than the large pines are.
Scotts pine, Austrian black pine (rare), Japanese black pine, Eastern red cedar (juniper), Rocky Mountain juniper, some arborvitae and the various spruce are some of the best living Christmas trees. They grow somewhat slowly, are more cooperative with pruning and can live in tubs long enough to function as Christmas trees for a few years. When they eventually get too large for their pots, they are not so likely to get too large for the garden.
Whether a Colorado blue spruce being retired after ten years of service or an Italian stone pine being retired after only a single Christmas, a living Christmas tree needs some help with the transition from pot to garden. Any circling roots should be severed when the pot gets removed. Otherwise, roots become constricted as the circling roots grow and expand.
Much of the dense foliar canopy should be thinned out to compensate for confinement of roots. Besides, much of the shorn growth is actually disfigured and will eventually get replaced and shed as new growth develops above the original canopy. Formerly pruned spruce, redwood, deodar cedar and most pines may need minor trimming of the upper new growth to promote a single leader (that will develop into the main trunk).
It is best to plant living Christmas trees rather soon after Christmas so that they can loiter in the garden through winter. Rain and cool temperatures keep them from desiccating as their roots start to disperse before new foliage starts to emerge in spring. Newly planted living Christmas trees should be watered somewhat regularly during their first year because their roots take some time to disperse adequately.
Pittosporum undulatum is a large shrub that can become a small tree.
Shrubbery behaving badly can be a problem. Many seemingly innocuous shrubs get planted in situations where they do not fit, and soon get too big for the space available. Others do not get shorn or pruned as they should, or simply get neglected, and eventually get overgrown. Many others have sneaky ways of sowing their seeds in awkward places where they would not otherwise get planted by anyone who knows better.
Most home improvement shows on television would simply recommend removing obtrusive, overgrown or inappropriate shrubbery and replacing it with something more proportionate, appropriate and stylish. What a waste! Hidden within overgrown shrubbery, there are sometimes potentially appealing small trees that only need to be released from thickets of overgrowth.
Overgrown Australian tea tree, sweet olive (Osmanthus fragrans), xylosma, glossy privet, ‘Majestic Beauty’ Indian hawthorn, and larger types of oleander, holly, pittosporum, cotoneaster and juniper are often easily salvaged by aggressive selective pruning rather than indiscriminate pruning for confinement. Lower growth that has become obtrusive, disfigured or otherwise unappealing can be thinned or removed to expose substantial sculptural trunks within. Upper growth that is out of the way can be left intact or thinned as necessary, but should not shorn or pruned indiscriminately. This creates informal small trees with distinctive trunks from what had been overgrown shrubbery.
Some shrubbery may need some time to grow out of its former confinement, and may be somewhat unsightly during the process. As they develop though, they should require less maintenance, since most of their growth should be up out of the way instead of where it is in constant need of pruning for confinement.
Many small trees that often get shorn into shrubbery would similarly do better with selective pruning to enhance natural branch structure and eliminate congested thicket growth. Japanese maples, redbuds, smoke tree, English hawthorn, crape myrtle, parrotia, loquat, strawberry tree, Pittosporum undulatum, and small types of magnolias, acacias, and yew pines (Podocarpus spp.) are notorious for getting shorn into unmanageable shrubbery. Pineapple guava, photinia, toyon, hop bush, larger types of bottlebrush and smaller types of melaleucas are more conducive to being shorn and pruned as large shrubbery, or can be pruned into small trees if preferred.
Tony Tomeo 