A Gardening Journal

Purple-leaved Mimosa

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Purple foliage, feathery foliage: Here's a tree that does both: Purple-leaf Mimosa, Albizia julibrissin 'Summer Chocolate'.

 

Think about it:  What other purple and feathery foliage is there?  Purple-leaf wisteria?  Nope.  Purple-leaf bush clover?  Nope.  Purple-leaf trumpet vine?  Nope.  Purple-leaf locust?  Well, yes, actually—but as you'll see on "Geek" in just a few days, not nearly as dark or feathery.

 

All of these plants are members of the gigantic Pea family, whose many hundreds of members are essential to gardens and landscapes and agriculture world-wide.  But only 'Summer Chocolate' pairs intensely ferny foliage with a rich burgundy coloring that rivals any Japanese maple, smoke bush, or beech.

 

And not even the most cut-leaf Japanese maple has leaves this large, let alone this happy in blazing dog-day sun.  In fact, the leaves of 'Summer Chocolate' emerge green in late Spring, and only achieve their darkest color with heat and sun.

 

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Finally, a purple-leaved "woodie" whose foliage doesn't just hold on to its dark hue—grimly or even desperately is the usual mind-set—as Summer gets its driest, hottest, and sunniest.  These purple leaves celebrate Summer.

 

 

Here's  Summer Chocolate in bloom.

 

Here's how to grow this heat-loving ornamental tree:

 

Latin Name

Albizia julibrissin 'Summer Chocolate'

Common Name

Purple-leaf Mimosa

Family

Fabaceae, the Pea family.

What kind of plant is it?

Deciduous flowering tree.

Hardiness

Zones 7 - 10.

Habit

Upright and spreading, with notably horizontal branches off a short single trunk.

Rate of Growth

Fast.

Size in ten years

Taller and faster in warmer climate zones. To twenty feet tall and fifteen feet wide.

Texture

The ultimate in feathery foliage in any tree with even a ghost of a chance being hardy into Zone 6.  A supremely airy and layered look.

Grown for

its foliage. The graceful burgundy leaves are doubly-pinnate, with leaflets from the main "backbone" of the leaf being little feathery things themselves.  The leaves, then, are fractal: each leaf's overall geometry—pinnate—is repeated in its leaflets—pinnate, as well.  And those leaflets' leaflets, so to speak, are the minutest any tree with, as I say, even a ghost of a chance at being hardy into Zone 6.  A scant half-inch long at best, they're an even scantier eighth-inch wide.  Some tropical pea-family trees have foliage that's even finer—but none of those start out green and darken to purple and bronze in Summer's heat and sun.   

 

its petal-free ("apetalous" is the Latin) flowers, which are "poofs" of long thin stamens, pink at the top but white at the bottom.

 

its toughness:  Despite its almost excessively-dainty foliage, Albizia tolerates sun, heat, and drought.  It needs supplemental watering only to get established, and can handle sandy soil and near-desert dryness without irrigation thereafter.

Flowering season

Summer: July into August.

Culture

Sun, heat, and well-draining and even lean soil.  Growth is faster with richer soil and more water, but hardiness is more certain with soil that's not very moisture-retentive.

How to handle it

Except in the mild end of its hardiness range—Zone 9 and 10—plant on a slope to ensure maximum drainage in the Winter.  Sandy and even gravelly soil is fine.  Water the first summer to get the tree established; it can pretty much handle itself thereafter.

 

The naturally-graceful branches spread widely and in layers, making only a dappled shade.  Albizia, then, would be a sensational partner to large- as well as colorfully-leaved plants that also demand excellent Winter drainage, and also wouldn't mind the lightest shade during the hottest months: Agaves, kniphofia, phormiums, yuccas, kalanchoes, cacti, iris, sedums, and low-growing sandy-soil-friendly palms.

 

The flowers are helplessly and restrictively pink and white, don't forget, so partner with species that flower only in rose, white, blue, burgundy, or, of course, pink itself.  Even pale yellow would, to my eye, be a mistake; anything even remotely orange or red—apricot, say—would be cringe-worthy in the extreme. 

 

'Summer Chocolate' would be a fantastic canopy for pink and blue hydrangeas, providing the ultimate in texture and color contrast in the foliage, texture contrast but color harmony in the flowers—and the light shade that would make the rich-soil and moisture-loving hydrangeas even possible.  Just be sure that the Albizia is planted higher than the hydrangeas, as well as to their southwest, to ensure that it gets the maximum drainage despite the hydrangeas' need for watering, and that the hydrangeas get the maximum shade from the Albizia

 

I've seen 'Summer Chocolate' hilariously happy in Zone 7 west of Philadelphia, but only in extraordinarily sheltered and sharply-draining sites could it be expected to survive north and east of New York City.  (I've proved this personally, and several times over.) 

 

I'm now growing a 'Summer Chocolate' in a container, and hope to overwinter it leafless and dormant in my basement.  Because this potted tree will be frost-free year-round, I don't have to "plant on a slope" to increase hardiness.  (It's a quickly-draining container, too.)  So I can pot in rich soil and water freely all Summer to help the plant grow as fast as possible.  We'll see.

Downsides

Albizia can self-seed to the point of invasiveness in Zone 8 - 10; seeds from 'Summer Chocolate' will almost always be just green-leaved, as well.  But in Zone 7, let alone anywhere colder, self-seeding isn't usually a problem.

Variants

Albizia julibrizzin 'Rosea' is the much-hardier mimosa seen down even into Zone 5.  There are Zone 7-and-up variants with pure-white or even yellow flowers.  All are so similar in size and habit, though, that it would be difficult to see having more than one or two.  And because only 'Summer Chocolate' has purple leaves in addition to the usual feathery foliage and poofy pink flowers, it's probably the "category killer," at least in Zone 7 and up.

Availability

On-line.

Propagation

By cuttings; 'Summer Chocolate' does not come true from seed.

Native habitat

Albizia julibrissin is native to Central and Far East Asia, from Iran all the way to Korea and Japan.  'Summer Chocolate' was a naturally-occurring seedling found in Japan in 1990.  The tree is named after the Florentine gentleman who introduced it to Europe in the 18th Century, Filippo degli Albizzi.  Yes, two "z" in Albizzi, but only one in Albizia.  Julibrissin sounds weird because it is: It's a corruption of the Persian for "silk flower."  Well, now you know, too.

 
 
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