A Gardening Journal

Today in Key West: Bismarck Palm

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Your first glance at a Bismarck palm will be because of its huge fronds. They are steel-blue at the darkest; the fronds of some individuals are nearly silver. Is this a living tree, or a massive metallic sculpture of one? Despite its surreal coloring, Bismarckia nobilis is for real.

 

The tree's startling qualities only multiply when you step in for a closer look. The thick long leaf stems—the petioles—are even paler than the leaves. Their icy-white color is overlaid with what, if you touch, you discover is a velvety tan fuzz. Very young leaves, hidden in the upper center of the large canopy, are smoothly sheathed with it, but much of the fuzz of mature leaves is shed as the stem beneath it expands into maturity.

 

The fuzz of this tree's petioles has matured to a stippling of nearly Serengeti suavity, like the pale coat of a rare predator cat. The petioles can be five or six inches thick even along the shaft, and at the base they widen to a foot or more. What with the speckling, the effect is of the rippling-lean legs of animals brought together, impossibly, as a tree. 

 

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The tree below has added the third astonishing element of the Bismarck palm's display: the inflorescence. The thick stem supports side stems that branch into threes, bearing tightly-grouped brown flowers.

 

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The flowers mature to berry-like fruits that start out green...

 

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...but mature to a brown the color and shine of coffee beans. The contrast in form, texture, and coloring with both the fuzzy petioles and, more at a distance, the blue leaves overall, can't be bettered when the fruits are fully mature, as in the picture below. Alas, this tree lacks talent in maturing its fuzz: Instead of the "Serengeti stipple," the fuzz seems to persist except where rubbed off by emerging inflorescences or—this individual being right on the street, and its crown still at eye level—by the hands of curious passersby.

 

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But, please, all possible points for the mature-fruited inflorescences with the blue leaves as background. And two points for the color of the fuzz, minus one for its dinged-up condition.

 

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The large palmate fronds are startling in shape as well as color. The central rib droops seductively, bringing its immediate skirting downward even as the skirts to either side maintain their upward flair. If the fuzzy petioles are channeling African cats, the leaves are channeling the swirling skirts of flamenco dancers who, unaccountably, have eschewed their usual hot-colored fabrics. Scandinavian flamenco dancers, perhaps?

 

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Overall as well as in detail, Bismarck palm is a stunner.

 

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Its size and need for hot sun year-round make Bismarckia nobilis a challenge as a container or conservatory specimen in the North. But where it can be grown outdoors, the tree is a siren that summons sophisticates back again and again.

 

Here's an introduction to a equally stunning blue-leaved fan palm, the oh-so-rare Cuban native, Copernicia fallaensis. It isn't quite as hardy—and also enjoys soil that is a bit more moisture-retentive—but its scale and nearly overwhelming visual impact are similar.

 

Here's how to grow this extraordinary palm:

 

Latin name

Bismarckia nobilis

Common name

Bismarck palm

Family

Arecaceae, the Palm family.

What kind of plant is it

Palm tree.

Hardiness

Zones 9b to 11.

Habit

Single-trunked and vertical, with a thick trunk topped by a broad rounded head of enormous fan-shaped fronds.

Rate of growth

Medium; faster when it receives additional water and nutrients.

Size in ten years

Depending on the climate and the culture, twelve to eighteen feet tall. The trees develop a full-size, fully-rounded canopy of fronds even as youngsters, so are wider than tall until their trunks top twelve to fifteen feet. Young Bismarckia palms, then, might be only fifteen feet tall—but twenty feet wide.

 

Potentially to sixty feet tall with a canopy of about twenty feet wide or wider. Unlike some other palms, such as Washingtonia, that retain old fronds indefinitely unless they are pruned away, Bismarckia fronds eventually abscise, leaving a clear and relatively smooth trunk.

Grown for

its large and extraordinarily colorful foliage: the round leaves can be ten feet across, and are held on thick stems—petioles is the Latin—that can be six feet long. The leaves are a startling blue color. They have a waxy surface that gives the fronds a bloom of such a silvery and metallic nature that it can seem, at first, that the fronds are actually inanimate sculpture, possibly constructed of aluminum. The petioles also have a waxy coating, of an even brighter and more unexpected color: white. As if this weren't interesting enough, the petioles are covered with fuzzy cinnamon scales that are shed, more or less, as the petiole matures. 

 

its elegant and regular form: The trunk is solitary and grows vertically. Like all palms with a strictly upright habit, Bismarckia is exciting when planted in groups, or in lines.

 

its tolerance of even the strongest sun, as well as its tolerance (when established) of drought.

Texture

The large palmate fronds are held in a very full and round canopy. A pie-shaped portion of the frond that's in line with the frond's petiole arches downward even while the remaining side portions of the frond maintain an upward arch. At first glance, the fronds appear to be doubled; the central "swoop" creates a luxurious feathery texture. 

Flowering season

In tropical climates that provide heat and sun year round, flowering can happen at almost any time. Judging from the performance of many specimens in Key West during a week in late February, individual trees at any age seem to set their own rhythms. Some were beginning to flower that week, some not at all, and still others bore multiple inflorescences of fully-ripe fruit. At the colder end of its hardiness range, Bismarckia will flower only in the warm months. Bismarckia trees are dioecious, and only the inflorescences of female trees bear flowers that mature to the stylish brown fruits in the pictures above.

Color combinations

The extraordinary foliage color of Bismarckia nobilis demands a respectful context if the tree isn't to look like a stunt. The leaves' grey-blue color and non-shiny surface suggest metal—aluminum, say, or a metal that has developed a whitish coat of oxidation. From a distance, almost any color could coordinate: yellow, pink, rose, orange, red, purple, or brown. The tan scales of the petioles, and the brown fruits of female trees, are showy only at closer range, but are so sophisticated and unusual that the colors above, which would harmonize with the steel-blue canopy overall, now seem distracting and even tawdry. See "Partner plants" and "Where to use it" for suggestions.  

Partner plants

Bismarckia is best partnered on the basis of its foliage's eye-catching color, the tree's strong overall form and large presence, the complex and sculptural interplay of the foliage with its petioles and their scales, and the stunning and contrasting inflorescences that, on female trees, mature to the contrasting brown fruit. It's a lot of considerations to juggle!

 

The easiest choice is to surround the tree with plants that are clearly deferential, and function as backdrop or groundcover. Select plants whose foliage is medium size and dark green; I'm hard-pressed to think of partner plants whose calling-card colors would be tan or deep brown, so direct links to the scales or fruits would be difficult. Although it would go with metallic blue as well as tan or brown, burgundy is a challenge, too: Who knows why, but there are no tropical plants of any size with burgundy foliage—no "copper beeches of Barbados"—and many of the ones that do have burgundy foliage, such as forms of Aechmea or Dracaena, have leaves large enough to seem heavy near the immense leaves of Bismarckia. For example: foliage of the gigantic 'Queen Emma' crinum is deepest burgundy when the plant is growing in full sun. Site on the hottest and brightest side of Bismarckia—but first consider if the thick, very long, and literally heavy crinum leaves are too weighty near the thick, very long, and literally heavy fronds of Bismarckia. Oh, for a purple-leaved fern!

 

Two glorious exceptions: The small leaves of Pittosporum tenuifolium 'Atropurpureum' are dark, and the shrub can become ten feet tall or taller. The poplar-shaped leaves of Euphorbia cotinifolia 'Atropurpureum' are purple when lit from above, and flame garnet when backlit; this tropical shrubby succulent can become almost tree-like in the same conditions that favor Bismarckia: Hot, sunny, and dry. 

 

With its sheer size, large foliage, and unique coloring, Bismarckia can "out-palm" almost any other; if at all possible, surround with non-palmy partners. This same intensity of sculptural display makes Bismarckia an awkward partner to plants whose best move is to burst into flower. With such arboreal drama nearby, mere flowers will probably seem superficial.

Where to use it in your garden

Bismarckia nobilis is one of the most powerfully focal of any tropical plants, and should be used only when it can be granted a large audience by its surroundings. When sited where it could become crowded, or planted just because of its unusual foliage, it tends to look uncomfortable. The dignity of its regular and full canopy is degraded if crowded; plant nothing as tall as Bismarckia nobilis within twenty or even thirty feet of it—except another Bismarckia nobilis: The tree's consistency of coloring and habit make it a natural for planting in groups.

 

Somewhere, please, there must be a tropical resort or corporate campus where a grove of Bismarckia is the focus of acres of lawn, or is the central planting in a huge courtyard. And, this being the tropics, could the face of the building at the back of the grove be painted raspberry or mango?

Culture

Full sun and almost any soil as long as it's very well drained.

How to handle it: The Basics

Plant at the beginning of the warm months; as is typical for any plant that thrives on intense heat as opposed to merely withstanding it, Bismarckia nobilis is most active when the weather is hot.

 

Water to ensure establishment, but the palms are used to hot and dry conditions, so "lead from behind" with any further irrigation. Water deeply when you do, then allow surface soil to become thoroughly dry.

 

Bismarckia also succeeds in containers, where growth is slower and overall size is less. Water and fertilize when in active growth in the warm months; omit fertilizer and water only sparingly, if at all, in cooler months, when the tree will be dormant. Provide all possible light if growing in containers that need to be moved into shelter in the cooler months: A portion of the sunlight is absorbed by the sheltering structure itself, even if it's glazing is glass or polycarbonate. Moreover, given the comparative weakness of the sun, and shortness of days, during the same months when containered plants will need to be brought into shelter, the need to maximize available light is only increased further. Unless strong supplemental lighting and heating are provided, overwintered specimens will be dormant (but will still retain their foliage) over the Winter. Water only enough to prevent wilting or shriveling of emergent foliage that is still dormant; increase watering only when growth has resumed in late Winter or Spring.  

How to handle it: Another option—or two?

The display of the intensely steel-blue fronds is glorious, in itself. The full show at the palm's canopy—the fronds, their silvery white petioles, the varying pattern of tan scales on those petioles, and the inflorescences of shiny ebony-brown fruits—is simply stunning in its scale and subtlety. Old fronds become a "dead" brown, and distract as well as hide outright much of this textural and aesthetic magic; prune them off as they occur.

Any (other) quirks or special cases?

The nuanced and dramatic display of the center of the canopy—the petioles and inflorescences, with the incredible steel-blue leaf blades themselves only as background—is only visible when you're able to look at it closely. The trunks of older Bismarckia palms can be twenty, thirty, forty feet tall and more, placing the entire canopy far too high for the center-canopy details to be seen; at that height only the overall enormous mass of the blue foliage would still be appreciable.

 

Alas, there's no way to stop the ever-increasing height of the trunk. As is typical for palms, all the growth potential of the trunk is at the top, deep within the base of the emerging new fronds. There is no ability to branch out if the top is pinched or removed. 

 

It would be an astounding dedication to an, admittedly, astounding tree, to plant it near a multi-story stairwell, whose exterior side, facing the tree, just happened to be all glass. Then the canopy center would be more-or-less in view throughout the life of the tree. Similarly, Bismarckia trees planted near multi-story buildings would offer their choice center-canopy view to a different story each decade.

 

In the real world, immense adult Bismarckia palms are thrilling by dint of their height and coloring, but the complex excitement of the center-canopy display, however, is only likely to be viewable when the trees are young—and, therefore, short. Enjoy the display while it's still accessible.

Downsides

Because the canopy attains full size even in young trees, which have short trunks, Bismarckia is a space hog. Only plant the tree where it has the necessary clearance—a circle twenty-five feet wide would be the minimum—right to the ground. Only after some years does the trunk attain enough height that the canopy can be walked under.

Variants

Despite its popularity, I'm not aware that any named cultivars of Bismarckia nobilis have yet been identified. There's an unnamed green-leaved form, which is less hardy, even, than the normal blue-leaved form. There are no other species in the genus.

Availability

On-line and, where hardy, at retailers. The palm is popular; given its unique, complex, and powerful charms, how could it not be?

Propagation

By seed.

Native habitat

Bismarckia nobilis is native to Madagascar. The name "Bismarckia" honors the the German Chancellor Otto von Bismarck. Hermann Wendland was a 19th-Century German who worked as a botanist and gardener; he wrote a monograph on the palm family that still informs the nomenclature of the Arecaceae. Johannes Hildebrandt, also a 19th-Century German, made trips to East Africa, including Madagascar, to botanize on behalf of the Berlin Botanical Garden. Hildebrandt brought back specimens of what became named Bismarckia, which was included in Wendland's seminal monograph. 

 
 
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