Dipteronia sinensis
We have many Acer species in the Flora
Wonder Arboretum, and also a Dipteronia sinensis which is closely
allied to Acer. In the trade they are referred to as “species
maples,” meaning anything other than the common forms of A.
palmatum, A. japonicum and A. shirasawanum. At the beginning of my
career J.D. Vertrees, the noted maple author and guru, asked me if I
was interested in the species maples, and I replied, “Not
particularly.” He responded, “You will one day.” I felt the way
I did because I recognized that my limited brain capacity would have
a difficult time to absorb obscure species with very limited market
potential. Besides, many of them didn't even look like “maples.”
When I was economically on my feet – though never well off – I
began to admire and collect species new to me, and I guess the old
codger was right after all.
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| Acer griseum |
I found that I could sell Acer griseum,
the larger the better, and it was a profitable species for me. Now
they are so plentiful that their price has declined, but I suppose
that Englishman E.H. Wilson would be happy to know that the tree he
introduced would become so popular and useful. It is commonly used as
a street tree in many towns and cities in Oregon due to its
ornamental qualities and because it is tough and durable in the
landscape.
Acer triflorum
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| Acer mandshuricum |
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| Acer mandshuricum |
Acer maximowiczianum
Acer x 'Cinnamon Flake'
Because of my initial success with A.
griseum I naturally moved into the realm of Acer triflorum, a
northeast China native with whitish-gray bark that exfoliates in a
different manner than A. griseum. You will find A. triflorum in snob
gardens and arboreta, but seldom will you see it in a typical home
landscape. Even more rare in the Trifoliata section is Acer
mandshuricum, the Manchurian maple. Its bark is dark brown and rough,
but not exfoliating like the previous two. My older specimen is one
of my first maples to leaf out in spring and one of the earliest to
display its wonderful orange-red autumn foliage. So I like A.
mandshuricum, but my customers don't know it, or even want to know
about it. The related Acer maximowiczianum is doomed because of its
cumbersome name, non-exfoliating bark and eventual large size. The
cross of A. max. with A. griseum has yielded A. x. 'Cinnamon
Flake', and that is a novelty that I can sell a few each year.
Acer micranthum
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| Peter Gregory |
*An excellent photo of the
Westonbirt tree can be seen on page 198 of DeBeaulieu's book, An
Illustrated Guide to Maples.
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| Acer pentaphyllum |
Acer pentaphyllum
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| Joseph Rock |
*I tried to pay homage to the
Strybing tree but was told by staff that it no longer existed.
Then I learned that one plant,
presumably a seedling offspring from the original tree in America,
could be seen at the Western Hills Rare Plant Nursery in Occidental,
California. The nursery and garden used to be a destination for
serious gardeners, having been founded by plantsmen Lester Hawkins
and Marshall Olbrich in 1960. Since I struck out at the Strybing I
drove to Occidental and found the nursery still in operation, but now
run by an Englishwoman. I toured the grounds and found a lot of
interesting plants, although I didn't find the old Acer pentaphyllum.
However there were a number of them in small pots on a bench in the
sales area. I asked the woman if they were grown from cuttings –
which I was doing at the time – but she responded that they were
seedlings. I said that I missed the mother tree, where is it? She
pointed straight up – we were standing right under it! Its canopy
was a broad umbrella-shape with the branches pruned up, so possibly I
could have walked under it a hundred times before noticing the
distinctive five narrow-lobed leaves. Fortunately the garden has been
preserved since the nursery closed in 2010, and as the Western
Hills Garden you can tour it on Tuesdays and Thursdays for $10
per person.
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| Acer pentaphyllum seed |
I was prompted into rehashing the A.
pentaphyllum story because yesterday I noticed seed on my largest
specimen. The problem with the species is that it is too tender to
grow outside in Oregon, and even though I have been growing it for
over 30 years, once a tree reaches the top of the greenhouse I sell
it to someone in California. My current specimen is about 12 years
old, and its amazing vigor is due to being grafted on “red maple”
rootstock, Acer rubrum. Years ago I planted this combination into the
garden, and the following winter we experienced a low of 5 degrees F.
By July I determined that the pentaphyllum was as dead as a doornail,
although rubrum rootstock sprouted from the base. I was hopeful that
the hardy rubrum would impart a hardy boost to the pentaphyllum top,
but not so, or at least not enough. I would encourage the next owner
of the Flora Wonder Arboretum – once I croak – to be a plantsman
of means and immediately construct a two-storied conservatory
to house the pentaphyllum.
Acer calcaratum
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| Acer calcaratum new growth in August |
Another tender – and rare – Chinese
species, Acer calcaratum, is also housed in the pentaphyllum's
greenhouse, and it too nears the top. The species grows in low-land
rainforests of Yunnan, Myanmar, Thailand and Vietnam. The specific
name calcaratum is from calcarate, and that from Latin
calcar meaning spurred. I've not noticed my tree in flower or
in seed, so I'm not sure what part is “spurred.” certainly it's
not the tri-lobed leaves which resemble an Acer buergerianum on
steroids. The best part is the reddish new growth which my specimen
showed off in spring, and is now showing off again. I foresee no
market for A. calcaratum, but for fun I will try to graft it on
another species – maybe A. pseudoplatanus.
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| Acer forrestii |
I notice that DeBeaulieu doesn't list
A. calcaratum, nor does he list A. forrestii, and the leaves of these
two species resemble each other somewhat. His Illustrated Guide to
Maples is sparse with synonyms, and without re-reading his entire
book I don't know where he “lumps” the two species. Even though I
can write a blog on obscure Asian maple species, I really don't know
them that well myself. I have seen a number of maples in the
Himalayan foothills, “foothills” meaning below 10,000' in
altitude, and in spring they can be beautiful with
reddish-to-chocolate-brown new growth. Since they generally aren't
hardy in Oregon I never felt compelled to bring them home.
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| Acer oliverianum |
Acer oliverianum was named by German
botanist Ferdinand Albin Pax in 1889 to honor English botanist Daniel
Oliver, an example where plant experts can overcome national
differences in the pursuit of science. The Chinese species forms a
strong-growing tree with a wide canopy at maturity. It looks like a
vigorous form of Acer palmatum, and in fact A. oliverianum is in the
Palmata section and is graft-compatible with A. palmatum. One
Japanese nurseryman whispered a secret to me, even though he was
alone with just me and my wife, that when using A. oliverianum as
rootstock, the variegated cultivars of palmatum would produce more
coloration. I doubt that he, or anyone in Japan, reads the Flora
Wonder Blog, so what's the harm to now present his theory? I tried A.
oliverianum myself as rootstock, but my variegates looked pretty much
the same as with palmatum. After three years the cultivars were
either sold or mixed in with the others so I can't report beyond
that. One concern would be A. oliverianum's hardiness – more or
less than palmatum? – and I suspect that coming from central China
it would be less.
Acer pycnanthum
Acer pycnanthum is a Japanese species
that is closely related to America's Acer rubrum. I used to assume
that the specific epithet was a corrupt spelling of Latin pyra,
which is from Greek pura for “hearth,” from pur for
“fire.” That assumption was because A. pycnanthum, like A.
rubrum, begins the spring with red flowers before leaves appear, then
finishes in fall with blazing red foliage. But wrong – the name is
derived from Latin pycnanthus for “having flowers in dense
clusters.” The maple is somewhat rare, growing in a limited
mountainous area of Nagano on Honshu Island. My girlfriend (at the
time) Haruko was surprised but pleased that I had a specimen in the
Arboretum, and perhaps that is why she agreed to marry me. She
graduated from the University of Tokyo's landscape architecture
department, and she remembers in her plant ID class that her favorite
professor beamed with pride when he pointed out the only specimen of
A. pycnanthum on campus. Haruko aced her class, then hurried to
America for nuptial bliss.
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| Acer sieboldianum |
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| Acer sieboldianum |
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| Acer sieboldianum 'Kumoi nishiki' |
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| Acer sieboldianum 'Sode no uchi' |
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| Philipp von Siebold |
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| Kusumoto Ine |
Acer sieboldianum – I don't have the
straight species in my collection, but a nice tree is growing at the
nearby Rhododendron Species Garden in Washington state. “Siebold's
maple” of course honors Philipp von Siebold, the German physician
and botanist who introduced numerous flora of Japan into Europe, and
who also kick-started the introduction of Western medicine into
Japan. Naturally he was attracted to Japanese women and he married
one; I can certainly relate to that. He fathered Kusumoto Ine who
went on to become the first female Japanese doctor, then court
physician to the Japanese Empress. Siebold's maple is compatible with
Acer palmatum as rootstock, and I grow the cultivars 'Kumoi nishiki',
'Mikasa yama', 'Sode no uchi' and the spreading, semi-weeping 'Seki
no kegon'. To the casual observer – and me too – A. sieboldianum
resembles Acer palmatum, although I haven't studied the former's
sexual expression. I agree with Hillier that sieboldianum is a “small
tree or large shrub,” but then the comparison with Acer japonicum:
“similar in ornamental merit...but with flowers yellow, not red...”
seems to be a strange description since they look so different. Am I
similar to a duck because we both have wide feet? Furthermore, M.
Yano in Book for Maples lists the 'Sode no uchi' cultivar as
belonging to the Acer tenuifolium species. Again, I don't know
the Asian Acer species expertly; and if I did I would only end up
arguing with other botanists, as they are a most contentious group.
For example, DeBeaulieu doesn't even list tenuifolium as a
species.
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| Acer pseudosieboldianum |
In any case botanists should probably
be outlawed from naming plants. The Japanese Acer sieboldianum was
first described by Dutch botanist Miquel and then the German botanist
Ferdinand Albin Pax in 1904 coined the specific name Acer
pseudosieboldianum for the similar species from Korea, China and
Manchuria. I really don't like pseudo for any botanic name
because if it's really a separate entity then let it's name stand on
its own and not be “like” or “false” something else. If a
Pseudotsuga is not a true hemlock then don't allay its name to
what is different. The worst plant name in horticulture is Acer
japonicum 'Aconitifolium', rendered since its leaves resemble the
Aconitum genus. The Japanese don't use the crappy Latin cultivar
name, rather they prefer Maiku jaku or “dancing peacock.”
Anyway A. pseudosieboldianum differs from A. sieboldianum because the
former comes from a different locale (and is more winter hardy) and
because the leaves are larger. Myself, I couldn't tell you the
identity of an older A. sieboldianum, A. pseudosieboldianum, or even
A. shirasawanum if asked to do so. In fact I have attended Maple
Society events where the world's botanists squabble about the
specific identity of a tree. I never take the bait and offer my
opinion because it wouldn't be “valid” anyway. Frequently, so as
not to come to blows, they throw up their arms and proclaim the tree
to probably be a hybrid anyway...then move on to the next argument.
Acer pubipalmatum
Most of us maple collectors wouldn't
know the difference between Acer palmatum and Acer pubipalmatum, and
pubipalmatum at best would just seem to be a variety of
palmatum. DeBeaulieu is a splitter in this case and gives
pubipalmatum specific rank while Hillier doesn't mention the species
at all. If you look closely you will see some minor differences, and
indeed pubipalmatum has finely hairy leaves. Besides the pubescent
leaves, pubipalmatum usually has seven lobes with the middle lobe a
little longer and pointing sharply.* It is also a stronger grower and
somewhat less dense than palmatum, and besides it is native to China,
not Japan. One could say that this Chinese maple is less refined than
the Japanese maple, and to be politically incorrect, my Japanese
father-in-law would say the same about the people.
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| Acer pubipalmatum 'Flying Daggers' |
*The cultivar Acer pubipalmatum
'Flying Daggers' has small leaves with more-narrow and pointed lobes
than the type. A Mr. Maple selection from North Carolina.
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| Acer pauciflorum |
Another palmatum look-alike is Acer
pauciflorum, but it is not listed in either DeBeaulieu's or Hillier's
book. My source for the “Few-Flowered maple” was Heritage
Seedlings and it was offered in their 2013-2014 wholesale catalog.
According to Heritage, “Almost unknown in the West, these are among
the first of seedlings to be offered in the U.S. Closely related to
Japanese maple, it is reported to be more drought and cold tolerant
than A. palmatum....Try a few and join us in an extensive field
trial.” Ok, I fell for the pitch and now I have some 7'
healthy-looking green-leaved trees. I'll keep a few away from sales
with the intention of rooting cuttings from them. If that goes well
I'll use them as understock and conduct a trial to see if it does
improve plants with “more drought and cold tolerance.” Or rather,
I won't trial. To really do it right would take at least half a
career, and I'm well on the downside of mine. Besides it would take
input from other growers from around the country to determine if A.
pauciflorum would make an improved rootstock. Hey young Man, why
don't you do the trial?
