A Gardening Journal

The Castor Aralia Greets the New Summer

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The Castor Aralia tree looked mighty prehistoric when we saw it in April.  In late June, it's a beauty.  Fresh green foliage radiates at the tops of all the new stems, and the burgundy leaf stems are a snappy contrast.  Lovely!

 

But this tree's beauty is more than skin-deep.  Looking down into the foliage...

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...the tree's prehistoric personality is celebrating the new season, too.  Yes, yes, yes, those burgundy leaf stems start, all of the sudden, from stems that are as fresh-green as the foliage.  Green, then burgundy, then green: a nice rhythm.  But the real shock is those thorns! 

 

They had matured to a warm mahogany on the stems that had overwintered, but they start out just as fresh a green as the leaves themselves.  Baby thorns: So adorable.

 

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They're not yet as ruthlessly rigid as they'll be as adults, but I still wouldn't want to grab ahold of a branch in a hurry.

 

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I'd coppiced this young tree in April, to encourage it to branch out.  And there must be ten or a dozen young branches just like this one, eager to show their stuff.  And come Winter, when all the thorns on all those branches show us their mahogany color for the Winter?  It will be a show worth revisiting.

 

 

Here's how to grow this proudly-protected tree:

 

Latin Name

Kalopanax septemlobus var. maximowiczii

Common Name

Castor aralia.  ("Castor" from the leaves' tropical size and resemblance to the castor-oil bean, the unrelated Ricinus communis.  "Aralia" from the club-like and (when young) aggressively thorny trunks and branches, plus the large and complex Summer flower clusters.)

Family

Araliaceae, the aralia family

What kind of plant is it?

Hardy deciduous tree

Hardiness

Zones 4 - 8

Habit

Upright, usually single-trunked.  Large palmate leaves look tropical in a temperate-garden context.  Young stems are impressively as well as colorfully thorny.

Rate of Growth

Fast when young; moderate when older.

Size in ten years

Fifteen to twenty feet tall, ten to fifteen feet wide.  Eventually to thirty or forty feet tall and twenty-to-thirty wide, i.e., of shade-tree size.

Texture

Depending on your priorities, the large foliage can look either lush or coarse.  Branching itself is sparse and heavy.

Grown for

Unusually large and "tropical" foliage.  Unusually late Summer flowering of very large (to two feet across!) and complex clusters of round heads of small white flowers.  Which bees adore.  Developing at the very tips of the new growth, the flowers are fully exposed, and are backed beautifully by the large leaves.  Young (as well as coppiced) plants are extremely thorny, which, again depending on your priorities, can be exciting or horrifying.  The overwintering buds for next Spring's foliage at the tips of young branches are impressively determined-looking.

Flowering season

High Summer: July and even August, when almost no other hardy trees are in bloom.  Check out the "Louis on the Loose" for July 19, 2011 to see a tree in full flower. 

Culture

Full sun, any soil that's well-drained. 

How to handle it

As a shade tree, just plant it and stay out of its way.  The lower branches, and the trunk itself, gradually grow out of their juvenile thorns.  Or, coppice in early Spring to keep as a large shrub that celebrates the fierce thorns but doesn't bloom.

Downsides

None

Variants

Maximowiczii has the most dramatically "fingered" leaves, with (usually) seven distinct lobes.  The species (as well as individuals) can be less fingered.

Availability

Thorniness of young plants usually dissuades all but the cogniscenti from buying this.  Too bad!  Head for "destination" specialty nurseries, or shop on-line.

Propagation

Grafting and seeds, and as well as an early-Spring chop-out of the occasional root sprouts from the mother plant.

Native habitat

China


 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 
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