A Gardening Journal

Full-moon Maple

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Round, pointed leaves in solid acid-green, sparked with heads of tiny rose-red and white flowers.  Look closer: The flowers also have pale sepals that tweet out to the bright leaves.  Full-moon maple: Could any hardy plant be more subtle—as well as more brilliant?

 

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The short, fat leaf-lobes have a fringed edge, but the real drama happens, in the Fall, in the leaf's interior.  See "Grown for its foliage," below, for details.

 

Acer shirasawanum 'Aureum' is as stunning in medium-range.  Although the trunks of the tree are upright and even narrow, the branches tend to the horizontal.

 

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The result is tiers of glowing foliage that are gracefully separated by sections of vertical trunks and limbs.  In my book, this is a tree that does nothing except the miraculous.

 

 

Here's how to grow this stunning maple:


Latin Name

Acer shirasawanum 'Aureum'

Common Name

Full-moon maple

Family

Included in Sapindaceae, the Soapberry family.  Other experts split it into its Aceraceae, the Maple family.

What kind of plant is it?

Deciduous tree.

Hardiness

Zones 5 - 7 in eastern North America; to Zone 8 in cool-Summer locales such as the Pacific Northwest, Ireland, or the British Isles.

Habit

Multi-trunked and upright; normally taller than broad.  The tree is so slow-growing that it will look like a shrub for years.  Eventually it grows tall enough, and reveals enough of its lower limbs and trunks, to read like a small tree.

Rate of Growth

Slow. 

Size in ten years

Eight to ten feet tall, six to eight wide.  After many years, fifteen to twenty feet tall and twelve to fifteen wide. 

Texture

Graceful.  Thanks to the alternation of tiers of foliage with open segments of branching, this is one tree whose presence is vivid but not heavy. 

Grown for

its foliage.  The palmate leaves have 11 to 13 lobes, so many that the leaves are only a lobe or two shy of being circular.   For a maple, the lobes are short and fat, and leave most of the interior of the leaf unserrated. 

 

The leaves emerge a brilliant and even acid green-yellow; they soften over the Summer but remain clearly yellow.  With the right combination of cool but only barely-freezing nights in Fall, the lobes turn red-orange while the large interior of the leaf remains yellow.  It's a fairly smooth line of transition across the base of each lobe, from the lobe's red-orange to the original yellow that remains in the leaf interior.  The result is a rounded expanse of yellow that does, indeed, have credible claim as a full-moon.

 

Because the "moon" is brighter than the lobes, it appears to be in front of them.  Overall, a full-moon maple in "full moon," will have hundreds of such moons dancing in front of what seems to be the larger body of foliage.  The display isn't long-lived: One serious frost and it's done, either because the moons transition to red-orange, too, or the foliage falls.  And some years, it doesn't happen at all.  Especially if you've never seen the display before, try not to be out of town for more than a day or two while waiting for your full-moon to, so to speak, moon-up.

 

In maritime climates, such as that of Britain, Fall can be so gradual and so lengthy that the foliage doesn't color well, let alone progress to "full mooning."  One of the classics of British gardening books, "Right Plant, Right Place," says outright that the Fall foliage of A. shirasawanum 'Aureum' is "not exceptional."  No surprise, then, that it doesn't list "full-moon maple" as the common name.  For once, I'm delighted not to be gardening across the pond.

 

its overall habit, at least when mature:  Tiers of foliage are well separated by open segments of branch and limb.

Flowering season

Mid-Spring, after the leaves have emerged.  The flowers are tiny, in dense clusters that are held above the foliage.  Their rose-red sepals contrast beautifully with the glowing gold leaves.  They mature to a maple's typical "two-paddled" fruits, dry bi-winged things known as samaras, that dangle in clusters beneath the foliage.  Happily, the samaras are also bright rose-red, at least when young; they mature to brown.

Color combinations

When its foliage is young, 'Aureum' is, quite possibly, the brightest—the most aureated—of any hardy plant.  Together with the small-but-contrasting clusters of red flowers and red samaras, the color of the tree's preferred neighbors couldn't be clearer:  Green, both light and dark; red and outward from red to orange as well as to burgundy.  The flowers and samaras are effective only into late Spring, so from July onward, the foliage, which has by then toned down to chartreuse, is the only color cue. 

 

Fall foliage can be variable, depending on the tree, the overall climate where you're gardening, and the specifics of that particular season.  As fervently as I try to hold to thoughtful color pairings the rest of the year, by Fall, I tend to toss out color rules:  The the more the merrier.

Partner Plants


With a plant as exceptionally vivid as well as elegant as Acer shirasawanum 'Aureum', invoke a gardener's version of the Hippocratic oath:  "First, do no harm."  Plant nothing near this tree that will compete with it, let alone conflict with it.  When in doubt, plant something that is less colorful, not more. 

 

Dark foliage is the universal complement to bright.  I sited my 'Aureum' where it is because I needed to establish a tall yew hedge immediately to its back.  In front of it is the very dark-leaved and spiny growth of the broadleaved evergreen, Osmanthus hetrophyllus 'Fastigiata'.  The small needles of conifers, as well as the feathery growth of the fan-spray conifers such as Chamaecyparis, Cryptomeria, Thujopis, and Thuja, are all excellent contrast in texture alone.  Compared to the electric yellow of 'Aureum', softer-yellow conifer cultivars harmonize as yellow-green.  I have an espalier of Cryptomeria 'Sekkan Sugi' near my 'Aureum'.  Bright-yellow ones, such as Chamaecyparis 'Fernspray Gold', are likely to seem competitive and disruptive.

 

The rounded and sharply-pointed leaves of 'Aureum' are effectively contrasted with smooth-edged foliage of almost any size, although larger is always better.  I have Tilia 'Winter Orange' as an espalier at one side of my 'Aureum', and on the other, Aristolochia durior up wires to the roof. 

 

Although it couldn't be more intense and high-spirited, the foliage of 'Aureum' is absolutely uniform in coloring.  Plants that are variegated, then, are not only no threat to its supremacy, they are a welcome touch of jazz near a plant that can be, otherwise, almost forbidding in its spectacularity.  Because 'Aureum' is typically narrow at the base, partners that are mounding and even dense are particularly welcome.  On both counts, I've chosen Orixa japonica 'Variegata'; for a quieter complement, consider Ilex crenata 'Bee Hive' or Rhododendron x laetevirens.

 

The singular foliage and habit of 'Aureum' make the opportunity to pair with a scandent or climbing plant very tempting, especially one that flowers later in the season, when the tree offers only chartreuse.  Someday, I'll get around to establishing a dark-flowered clematis between my 'Aureum' and the nearby orixa; it can extend a few (and only a few) tendrils and flowers out to both.  See the Plant Partners of the orixa article for the list of some of the dark-flowered clematis possibilities.

 

At ground level, Acer shirasawanum 'Aureum' is welcoming of underplanting with species and cultivars with a diversity of talents: dark foliage, large foliage, ferny foliage, variegated foliage, grassy foliage.  So far, I have a mash-up of two aggressive colonizers that touch several of those bases:  Podophyllum peltatum and Carex muskingumensis

Where to use it in your garden

Acer shirasawanum 'Aureum' is a star, and demands your most respectful and celebratory siting.  The tree's details are as mesmerizing as its gestalt so, if at all possible, don't  do what I did: plant the tree at the back of the deep bed that provides no realistic access for close inspection.  By all means, surround with effective plant partners—but also provide the opportunity, even if only by a few narrow stepping stones, for high-powered study of the flowers, the samaras, and the foliage.  This is a plant that you'll want to thank in person, with a grateful hand on the trunk and a few words uttered so quietly that only the tree and you hear them.

Culture

Full sun only where Summers are cool and the tree won't experience drought stress.  The safest siting is in dappled or afternoon shade, in good well-drained soil and with enough water.

How to handle it:  The Basics

Full-moon maple is a tree to plant and then leave largely alone.  It needs little if any formative pruning, and can grow on its own for many years with no more attention than to clip off the occasional dead twig.  Plant in Spring or Fall, and be sure to water sufficiently to encourage ready establishment. 

 

Maple trees are characteristically comfortable with being transplanted (carefully and with respect, let alone all possible equipment and crew) at any size, as well as growing long-term in containers.  So you can sometimes find large specimen trees, either balled-and-burlaped or in nursery boxes, at "carriage trade" nurseries.  Given how slow the trees' growth is, their price will be dizzying.  Expect to pay hundreds of dollars for an individual taller than five feet, and, depending on its age and trunk caliper, one or even several thousand dollars for a full-moon nearing ten feet.  The sky's the limit for specimens even larger.  Although Acer shirasawanum 'Aureum' is thrilling at any size, it is, nonetheless, worth it to buy the largest you can. 

How to handle it: Another option—or two?


With growth so slow already, restrain yourself from pruning anything but the occasional dead twig.  Removing living branches also removes the foliage they bear, which would only slow down growth further.

 

If you were lucky enough to have purchased a property with a mature full-moon maple, or to have planted one in a garden that you're still nurturing twenty years on, or to have been able to lay out the big bucks for a hefty specimen, you'll have opportunities for a limited and intensely-contemplated amount of pruning of live growth of your fairly-mature specimen. 

 

Unlike the pruning I so often propose for plants featured here, full-moon maples are not pruned to control size, nor to encourage quicker new growth, nor to shape into espaliers or topiary.  For once, the goal is exclusively to enhance a plant's natural—and naturalistic—habit and size.  Consider whether removing a small number of twigs, branches, or even (but think carefully) limbs could bring an even higher level of grace and drama to your specimen.  Growth naturally becomes open with age, creating a deeply-moving counterpoint of exposed portions of branching amid planar clouds of shimmering foliage.  Could a bit more of this or that branch be exposed, even though that means removing a bit more of this or that amount of incredible foliage?  If a lower limb were removed entirely, would the benefit be a more telling reveal of the base of limbs and the trunk itself?  The secondary branches, and therefore the foliage they bear, tend toward the horizontal, creating a canopy of foliage that is a nearly iconic "artistic" embodiment of a congeries of foliage layers of infinite delicacy, levitating in joyful repose.  Don't make any quick moves: It would take years for the tree to grow enough to cover the gaps created by unwise cuts.

 

When in doubt, do less or, even, do nothing.  Return to the tree in a month, or even a year, for another session of meditative and only modestly-productive interaction with this remarkable cultivar.

Quirks or special cases


None.

Downsides

Acer shirasawanum 'Aureum' is very slow-growing, and larger-sized specimens are as rare as they are expensive.

Variants

'Aureum' is, normally, everyone's first choice among A. shirasawanum cultivars, but there are several dozen others to consider.  The foliage of 'Fall Moon' is blushed with orange all season long.  That of 'Mr. Sun' is yellow-green and much more deeply serrated.  The leaves of 'Sensu' are more serrated still, with red tips and petioles; given that the name means "moving fan," the foliage is described as catching any breeze with particular grace.

 

There are also dwarf cultivars, as well as cultivars that are full-size but with dwarf leaves.

 

Many Acer shirasawanum cultivars are presumed to be hybrids with Acer palmatum and its cultivars, and regardless of their merits as such, will look like "just another Japanese maple."  It would seem like a fetish that's entertained at the expense of a garden's broader merits in design and diversity to have more than the occasional and prominently-sited Japanese maple, regardless of its actual species and cultivar.  Given that the common name of Acer shirasawanum is always full-moon maple, growing cultivars whose foliage shape (being too deeply serrated, say) and coloring (some forms have purple or just green foliage) would deny that possibility seems tone-deaf—especially if you didn't also have the full-moon maple itself, A. shirasawanum 'Aureum'.  That would be comedy (at your expense) as well as tragedy.    

Availability

On-line.

Propagation

By grafting.

Native habitat

Acer shirasawanum is native to Japan.

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