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Tasmanian Tree Fern

Tasmanian tree fern is more tolerant of significant frost than Australian tree fern is.

The trunk of a tree fern is really just tough compressed roots growing downward through dead organic material left behind by earlier growth. The foliage and terminal shoot high on top is just like any other fern that never leaves the ground. Because such a trunk is porous, it is ideal for epiphytic plants that, in the wild, mostly cling onto trees instead of growing on the shadier forest floor. Even though most epiphytic plants are able to cling to just about anything, many prefer tree fern trunks because they can actually root into them.

The shaggy trunks of Tasmanian tree fern, Dicksonia antarctica, take decades to grow tall enough for smaller plants to be visible below the lush foliage, but are plump enough to host a rowdy party of  clinging epiphytes. Most get only about four or five feet tall, with the foliage standing a few feet higher, although some old specimens in Golden Gate Park are more than fifteen feet tall, and very old specimens in their native Tasmania can get nearly fifty feet tall.

The big lacy leaves spread about six feet wide, and can reach twice as wide in shadier spots. Shade also makes the foliage darker rich green. Like almost all ferns, Tasmanian tree fern like relatively rich soil and regular watering. Unlike other tree ferns though, it tolerates frost.

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New Zealand Tea Tree

Frequent shearing might interfere with bloom.

Bloom should probably be most profuse for late spring or early summer. In actuality, New Zealand tea tree, Leptospermum scoparium, blooms whenever and however it wants to. Now that it seems to be blooming prematurely, it might continue to bloom in phases until autumn. Minor bloom phases might even continue randomly through autumn and winter.

Floral color is white, pink or red, including deep ruby red. The tiny flowers are sometimes sporadic but sometimes quite profuse. A few cultivars have plump double flowers. Foliar color is olive drab green or bronze green. The finely textured evergreen foliage is slightly scratchy. Its tiny leaves have pointed tips. The fibrous brown bark is handsomely shaggy.

New Zealand tea tree works very well as a blooming informal hedge. Frequent shearing of formal hedges compromises both bloom and natural form. Elimination of lower growth exposes appealingly sculptural trunks supporting little trees. Some modern cultivars will not reach first floor eaves. Some reach second floor eaves. All demand sunny exposure.

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Cork Oak

Cork oak develops sculptural trunks and branch structure with striking bark texture.

Portuguese neighborhoods in San Jose and other big cities might be identifiable by the presence of the otherwise rare cork oak, Quercus suber. After all, they are native to Portugal, as well as Spain, Sardinia, Corsica, Sicily and the coast of the Mediterranean Sea as far east as the eastern tip of Italy on the north, and the northwest corner of Libya on the south.

Like redwoods, cork oak is one of the few species of trees that survive forest fires by being less combustible. Their foliage and small twiggy stems may burn, but larger limbs and trunks are insulated by very thick cork cambium (bark). Most other trees that are adapted to burning either disperse their seeds as they burn in order to get a head start at reforestation afterward, or simply resprout from their roots.

 Ironically, this bark that is intended to help the trees survive was actually the reason why trees on the north coast of Algeria were so extensively and detrimentally harvested during French  colonialization. Corks made from the bark were needed for the wind industry in France. Fortunately, cork in Algeria is now harvested like it is in other regions, without harming the trees that produce it.

Compared to other oaks, cork oak is not too large. It can get a bit more than fifty feet tall and nearly as wide, but takes a century or more to do so. It can actually stay proportionate to urban landscapes for a very long time. Roots are mostly complaisant. The main problem with cork oak is that it drops its evergreen foliage constantly, and drops floral debris and acorns for a few months.

Gnarly trunks and limbs with spongy bark are the main appeal. The one and a half or two inch long leaves are not so interesting. They are barely convex, often with a few blunt lobes, and dull grayish green from below.

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Sweet Box

Sweet box should bloom for winter.

Floral fragrance is likely the primary asset of sweet box, Sarcococca ruscifolia. However, the splendidly glossy and evergreen foliage is as appealing as that of any of the various boxwoods. It is darker and richer green, with orderly arrangement on nimble and arching stems. Individual leaves are small but larger than boxwood leaves, and with pointier tips.

Sweet box blooms during winter, with deliciously fragrant but tiny pale white flowers that are not much to see. They are unlikely to get credit for their impressive fragrance without close investigation for its source. Vigorous plants may produce a few rich maroon berries that contrast delightfully with the rich green foliage. Cut stems work well with cut flowers.

Because it is naturally an understory species, sweet box not only tolerates partial shade, but actually prefers it. Harsh exposure fades its foliage. The dense foliage on wiry stems adapts to low hedging. It is better with alternating cane pruning to remove old stems and promote fresh basal growth. Overgrown specimens respond quite favorably to coppicing. They grow to three feet high.

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Atlas Cedar

Amy Carter had the most boss treehouse in an Atlas cedar.

My generation can remember when Amy Carter, the daughter of former President Carter, got a treehouse built in a mature Atlas cedar, Cedrus atlantica, at the White House. It was so cool that it was ‘boss’! Besides being more luxurious than a typical treehouse, it was designed by President Carter to not damage the tree even slightly.

Here in the west, most Atlas cedars are cultivars (cultivated varieties) with blue foliage that often rivals that of Colorado blue spruce. Most have strictly horizontal or angular limbs with stiff, densely foliated branches. Some are so pendulous (weeping) that they need to be staked to be kept off the ground. They actually look great trained along the tops of retaining walls, even without staking, with their blue foliage cascading over. Others are strictly upright and narrow. Colorado blue spruce may have better color; but Atlas cedar has more interesting variation of form.

It is also better adapted to the local Mediterranean climate than spruces and other conifers are, and gets much larger. Mature Atlas cedars can get as tall as a hundred feet, with trunks as wide as five feet.

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Sweet Olive

Sweet olive hides its fragrant bloom.

It may not seem like much to take notice of. Sweet olive, Osmanthus fragrans, resembles glossy privet, but is neither as glossy nor quite as richly green. The dense and evergreen foliage can work about as well for a formal hedge though. It is even better as a small and billowy tree. It gets at least as high as ground floor eaves, and can reach upstairs eaves.

The primary allure of sweet olive is its delightfully pervasive and fruity floral fragrance. Its small and slender clusters of tiny pale white, yellow or gold flowers are mostly obscured by foliage. For those who are unfamiliar with it, the fragrance might be difficult to identify. Bloom is most abundant before and after summer. Sporadic bloom happens at any time.

Because sweet olive is more olfactorily appealing than visually appealing, it works quite nicely as in informal hedge behind prettier plants. It can stay narrow between windows of neighboring homes that are a bit too close together. If enough flowers are available, they might flavor tea and confectionery. A cultivar with variegated foliage is unfortunately rare.

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Grecian Bay

Grecian bay does not get as massive as the native bay laurel.

The native bay laurel should not be confused with the Grecian or sweet bay. Despite the similarities, the native bay laurel grows into a large tree. The foliage can be used as seasoning like Grecian bay, but has a very different and much more pungent flavor. It can often be found fresh in markets, labeled as Grecian or sweet bay, and has likely ruined all sorts of recipes.

Grecian or sweet bay,  Laurus nobilis, stays much smaller much longer. It takes many years to grow to thirty feet tall, often with many trunks flaring out from the center. Trees that are nearly twice as tall are ancient. Because of slow growth, Grecian bay can be happy in large containers as long as it is pruned to stay proportionate to the confined root system.

The three or four inch long, and inch or so wide leaves of Grecian bay can be difficult to distinguish from those of bay laurel. The minor differences are that Grecian bay leaves have slightly undulate margins with a few small and sometimes barely perceptible serrations (teeth) that bay laurel lacks. The leaf apexes of Grecian bay leaves are typically a bit more blunt. For culinary purposes, it is important to be aware that dried leaves and fresh leaves have very different flavors.

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Kalanchoe

Kalanchoes bloom with tropical fruity color.

Even if never as overly indulgent in bloom as when new, Kalanchoe blossfeldiana is one of the more sustainable of popular blooming florist plants. Forced bloom remains colorful for quite a while. By the time it deteriorates enough to necessitate grooming, new foliage may already be developing. Sporadic subsequent bloom is more natural in appearance.

Ultimately, Kalanchoe blossfeldiana becomes more of a succulent foliar houseplant that occasionally blooms, rather than a spectacular floral plant. Individual plants may survive for only a few years, but are likely to generate basal pups that grow as new plants during that time. Also, they are very easy to propagate by succulent stem and even leaf cuttings.

Mature Kalanchoe blossfeldiana do not get much more than a foot high and wide. Some may stay half as tall. Their lower leaves can get three inches long, with crenate margins. Minute yellow, orange, red, pink or creamy white flowers bloom for late autumn or winter. Garden plants require shelter from chill through winter and hot sunlight through summer. Most are houseplants that appreciate copious sunlight.

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Beaked Yucca

Beaked yucca resembles Cordyline more than Yucca.

The fifty or so specie of yucca that are native to North and Central America are horticultural nonconformists. Like most of the related agaves and aloes, they are classified as succulents; but none have succulents leaves. Their stems store moisture, but are about as succulent as trunks of palm trees. Actually, many are classified as trees because they develop heavy and sculpturally branched trunks, but they are really just big herbaceous perennials that get very old.

From the Big Bend region of Texas and adjoining Mexico, beaked yucca, Yucca rostrata, happens to be one of the yuccas that develops a trunk, but grows so slowly with such billowy foliage, that it respected more as a striking foliage plant. The largest and oldest plants get no larger than fifteen feet tall and rarely develop one or very few branches. Most are less than ten feet tall with single but bulky symmetrical foliar rosettes. The individual grayish leaves are limber and narrow, but very abundant. ‘Sapphire Skies’ has even more striking bluish foliage.

As if the excellent foliage were not enough, mature beaked yucca blooms with small white flowers on big spikes nearly two and a half feet tall. Spikes can appear through winter and are typically finished blooming by spring, before summer dormancy, but do not seem to be too devoted to any particular schedule.

Beaked yucca is less common than it should be; perhaps because it is difficult to grow in nurseries. Besides, they are not for every garden, and are very likely to rot where they get watered as frequently as most other plants get watered. They do not mind if watered perhaps a few times through summer, but are more than satisfied with what they get from rainfall.

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Mandarin Orange

Mandarin oranges are the earliest citrus.

Mandarin orange, Citrus reticulata, and nuts are some of the more traditional goodies for Christmas stockings. In Northern Europe centuries ago, nuts from the Americas were still exotic treats. The availability of perishable citrus fruits from Mediterranean regions relied on expensively efficient shipping. Consequently, citrus fruits were almost like delicacies.

Even when shipping was slow, Mandarin oranges ripened in time to arrive by Christmas. However, they needed fast shipping because they are more perishable than other citrus. They are innately more prone to oxidation because their rind and segments fit so loosely together. Of course, that is why they are so delightfully easy to peel, pull apart and share.

Mandarin oranges are smaller, more oblate, brighter orange, but also more variable than common sweet oranges. Among their many cultivars, their smaller leaves and thorniness are likewise variable. Very few very old trees grow taller than fifteen feet. Tangerines are merely barely genetically distinct Mandarin oranges that developed within the Americas.