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European White Birch

91127Like a flower girl scatters rose petals ahead of a wedding procession, European white birch, Betula pendula, tosses its small deltoid leaves soon after turning soft yellow with autumn chill. Color may not last long on the trees, but becomes a delightful mess for those who appreciate such assets. The primary allure though, is the slender strikingly white trunks, accented with black furrowing.

European white birch is very informal, but also elegant enough for formal landscapes. To best display their gently leaning white trunks, they are popularly planted in relaxed groups. Their canopies are neither broad nor dense, so a few fit together nicely. As lower branches get pruned away, pendulous upper branches sway softly in the breeze. Mature trees are mostly less than fifty feet tall.

Himalayan birch, Betula utilis or Betula jacquemontii, which has become more popular than European white birch since the 1990s, has a completely different personality. Its strictly vertical trunks and upright growth are appealing separately, but incompatible with European white birch. When adding trees to an established grove of any birch, it is very important to procure more of the same.

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Exfoliating Bark

P90720KBecause redwoods live for centuries, their bark gets very thick. They do not shed their bark as they grow. Old giant redwoods in the Sierra Nevada have bark that is a few feet thick and thousands of years old. Their bark is thicker than the trunks of what most of us consider to be large trees! Even much younger coastal redwoods that have regenerated here since clear cut harvesting about a century ago have bark that is a few inches thick.
They like their bark thick. It is the insulation that protects them from forest fires that incinerate other vegetation. Unlike most species here that are designed to burn and then regenerate more vigorously after fire, redwoods prefer to survive fire by being less combustible. As they mature, and their bark gets thicker, they become more resilient to fire. There are only a few species here that survive fire mostly intact, rather than regenerate after it.
Of course, survival is more complicated than mere thick bark. Redwoods, particularly coastal redwoods, also try to exclude other more combustible species from their forests. Also, they tend to shed lower limbs that would be more combustible during a fire, and prioritize higher and therefore less combustible canopies. Redwoods have developed a rather ingenious (but unfortunately ecologically delicate) systems of survival techniques.
Other trees are not so easy to figure out. Many species of Eucalyptus shed lower growth as if they want to be less combustible. They shed copious amounts of foliage and bark to inhibit undergrowth and other combustible vegetation. However, not only are they innately very combustible, but because they shed so much of their bark, they lack insulation from fire. It is as if they expect to burn back to the ground, and then regenerate after a fire.
Regardless of their logic, exfoliating bark of the larger eucalypti can be annoyingly messy. Exfoliating bark of some of the smaller eucalypti can be rather appealing in home gardens. This tree happens to be the same featured last week in ‘Silver‘.P90720K+

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European White Birch

60120+It may not be the biggest or best deciduous shade tree, but European white birch, Betula pendula, is famous for tall and elegant white trunks with wispy pendulous stems. It is a very informal tree that typically leans in one way or another, but is somehow right at home in refined landscapes. It is rarely alone, since it is usually planted with two or more friends, and sometimes in groves.

Not many of the biggest European white birch trees are more than fifty feet tall locally. (They can get bigger in cooler climates.) The slender trunks do not get much more than a foot and a half wide. As trees mature, the smooth white bark develops rough black furrows. The small triangular leaves turn soft yellow in autumn. The somewhat sparse foliage makes only moderate shade.

‘Laciniata’ has lacy lobed leaves, and stands straighter and narrower. ‘Youngii’ is so pendulous that it can barely stand up without staking.

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Some Plants Impress With Bark

P80805Lemon eucalyptus, ‘Marina’ madrone, cork oak and all sorts of melaleuca trees are known more for their interesting bark than for their foliage or flowers. It helps that their distinctive trunks and branch structures are ideal for displaying their unique bark. Color and texture of bark is remarkably variable, and tends to get noticed more in winter while blooms and foliage are lacking.

Bark of sycamores, birches, elms and crape myrtles that had been so handsome throughout the year is more visible now that it is not partially obscured or shaded by the deciduous foliage that is associated with it. Trunks and limbs of European white and Jacquemontii birches are strikingly white. ‘Natchez’ crape myrtle has distinctively blotched bark, (although the white flowers are pale.)

Because of their other assets, English walnuts, figs and saucer magnolias are not often grown for their bark. Nonetheless, their pale gray bark shows off their stocky bare branch structure nicely, especially in front of an evergreen backdrop of redwoods or pines. The smooth metallic gray bark of European beech is much more subdued, but is what makes big old trees so distinguished.

A few deciduous trees and shrubs get more colorful as winter weather gets cooler. Instead of white or pale gray, their bark turns brighter yellow, orange or red. Some plants, like sticks-of-fire, do not need much cool weather to develop good color. Others get more colorful in colder climates, and contrast spectacularly to a snowy landscape. Locally, they should be well exposed to chill.

As the name suggests, the coral bark Japanese maple (‘Sango Kaku’) develops pinkish orange bark. It can get ruddier in colder climates, but may get yellowish here. Unlike other Japanese maples that get pruned to display their delicate foliage and branch structure, the coral bark Japanese maple sometimes gets pruned more aggressively to promote more colorful twiggy growth.

Osier dogwood is a shrubby dogwood that lacks colorful bloom, but compensates with ruddy brown, brownish orange or pale yellow bark in winter. (Dogwood bark . . . There is a pun there somewhere.) Because it lacks colorful bloom, it can be pruned aggressively after winter. Older canes that do not color as well can be pruned to the ground as they get replaced by new canes.

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Cork Oak

71115Like redwoods, the cork oak, Quercus suber, is a ‘pyrophyte’, which means that it survives forest fires that burn off competing vegetation. The trunks and main limbs are insulated with a very thick bark. Only the foliage and smaller stems burn off. After a fire, the upper limbs of cork oak regenerate new foliage while other less fortunate plants start over from their roots or seed at ground level.

The thick bark is really what cork oak is grown for. It is used for corks, gaskets, flooring, notice boards, cricket ball cores and too many other products to list. It is also quite handsome on the stout trunks and limbs of landscape trees. If only the acorns were not so messy, cork oak would be a nice drought tolerant street tree with complaisant roots. The hazy evergreen leaves are about two inches long. Old trees eventually get almost fifty feet tall.

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Crape Myrtle

70906There seems to be some discrepancy about the correct spelling of crape myrtle, Lagerstroemia indica. Many of us spell it as ‘crepe’ myrtle, thinking that crepe is the thin colorful paper that the flowers resemble. It is actually a rolled up thin French pancake. The thin paper is actually spelled as ‘crape’. Of course those of us who dislike the commonness of crape myrtle might omit the ‘e’.
There is plenty for horticultural professionals to dislike about crape myrtle. It is remarkably complaisant, and proportionate to small urban gardens. Consequently, it very often gets planted even where other trees would be more practical or proportionate. It is the most common street tree because it so rarely damages curbs or sidewalks, but does not get big enough to shade the street.
The biggest varieties do not get much more than twenty feet tall, so work well in utility easements. Trees might be on a single straight trunk where space is limited, or to display the appealingly mottled bark, they might have multiple trunks. The billowy white, pink, red or mauve blooms are spectacular in late summer. The deciduous foliage can get quite yellow, orange or red in autumn. Hard pruning in winter improves late summer bloom and autumn color.