Flora Wonder Blog: Maple Species from Japan (Part 2)

Buchholz Nursery Display Garden

Last week's Flora Wonder Blog featured Maple Species from Japan (Part 1)...to which I have an urge to conclude. I alluded in the previous text to some maples that the reader may not have ever seen. So here I'll be your guide-dog and we'll wander down yonder in the maple patch, and let's see how many you are familiar with, or can I present you with something new?

Something new – it might be for you – but the abundance of Japanese taxa has been well-documented, most for over 100 years. Many remain obscure in horticulture, though, and I doubt that a single species that I discuss below can be found in my hometown of Forest Grove, Oregon, even with the town's population of over 25,000 middle-classed souls with big yards. Yes, there are plenty of maples in Forest Grove, and we even have a Maple Street that's lined on both sides with medium-sized trees, but none of them hail from Japan. I'll admit that most Japanese maples are non-events, horticulturally speaking, but every one has some interesting quality, and indeed a few are highly ornamental, at least in my estimation, and those should be more widely known and grown. You won't find any in your box-store garden centers or in the herb-vegetable-and-annual type of plant venues because those dispensaries must eke out a living with the tried and true, and besides – no one working there, including the owner, has a clue about the merits of “obscure” Japanese maple species. Nevertheless, let's explore some examples, and one day perhaps, you, the reader, might grow excited enough to become this millennium's Johnny Mapleseed.

Acer nipponicum at Sir Harold Hillier Garden

Acer nipponicum

Acer nipponicum in September at Flora Farm

Other than in my own collection I've never seen Acer nipponicum except for in a few British arboreta. Thanks to Mark Krautmann of Heritage Seedlings, Oregon, I was able to purchase young starts of the rarely-seen species, and I suspect that his seed source was one of those British collections. I'm not sure why I'm attracted to Acer nipponicum, but I have a nice-sized tree at Flora Farm. It is splendid in spring and early summer, but when August brings sustained 95-105F days it can look dreadful. Furthermore, the resigned appearance of summer is never redeemed with bombastic brilliance in autumn, for the faded green leaves turn to dull yellow, and then to brown. I once asked Peter Gregory, the Acerian author and species expert from England, what rootstock to use to propagate A. nipponicum. His response – somewhat flippant – was to use Acer pseudoplatanus...because it “accepts most everything,” but I learned that “most everything” does not include A. nipponicum. The species is from Japan of course, for Nippon is an old name for Japan.* The Japanese people bristle at the term Nip in reference to themselves, and prefer instead Nihon, or Nihonjin for a person from Japan. Acer nipponicum is native to mountain forests but I have never seen it in the wild. Its foliage bears some resemblance to Acer tegmentosum, but the former is in the Section Parviflora, while the latter is in the section Macrantha. All of my A. nipponicum are seedling-raised then, and they all look the same. Since there is no compatible rootstock for it, can I conclude that there will never be any hybrids with other Acer species?

*The word “Japan” is an exonym, or a name that is used from outside the country. The nihonjin called their country Yamato in its early history, and they began using Nippon around the seventh century. Marco Polo was aware of Japan's existence though he never travelled there. He called the land “Cipangu,” based on the Chinese name meaning “sun source country.”

Acer tschonoskii

Acer tschonoskii is easy to pronounce once you get used to it (show no skee eye), and the name honors the Japanese botanist Tsugawa Tschonoski (1841-1925) who collected for Carl Maximowicz, head of the St. Petersburg Botanical Gardens. Eventually growing into a small tree, it begins as a sprawling shrub unless pruned into a more tight shape. The species is native to northern Japan and is plenty hardy in Oregon, indeed down to -20 F, USDA zone 5. I grew a few long ago but ultimately we did not bring out the best in each other. My originals were of seedling origin so there was a bit-to-considerable difference in all of them. Some thrived pompously while others lingered as if a decade or so didn't really matter, so as a crop too many dawdled to make growing profitable.

Carl Peter Maximowicz

Sugawa Chonosuke

Lilium leichtlinii subsp. maximowiczii

Betula maximowicziana

Carl Peter Maximowicz was mentioned above due to his employment at the St. Petersburg Botanic Garden, and before that he was a pupil of Alexander von Bunge and graduated in biology at the University of Tartu in Estonia in 1850. Max travelled extensively in eastern Asia and spent most of 1862 in southern Japan, following in the footsteps of Thunberg and von Siebold. And, for additional support, he was accompanied by his assistant Chonosuke, mentioned above with a different spelling. I have grown plants named in Max's honor such as Lilium leichtlinii subsp. maximowiczii, Betula maximowicziana and the large-growing Acer maximowiczianum, commonly known as the “Nikko maple.”

Rhododendron schlippenbachii

Berberis thunbergii

Acer maximowiczianum

Greater accomplishment was that Maximowicz described and named over 2300 plants, all new to science. Horticulturally, perhaps the best was Rhododendron schlippenbachii and Berberis thunbergii, with the latter being grown by the many, many thousands, even after I began my career. As for maples, he described and named Acer argutum, Acer barbinerve, Acer capillipes, Acer miyabei, Acer mono, Acer tschonoskii and Acer nikoense [sic] Maxim, with the latter more precedentally known as Acer maximowiczianum. I'll admit that I pursue Max's maple as a BIO plant, that is, of Botanical Interest Only, and that its brethren in the Section Trifoliata such as Acer griseum, Acer triflorum, Acer mandshuricum etc. are generally considered far more interesting in modern landscapes.

Acer maximowiczianum

Nomenclatural caution must be stressed to not confuse the above described Japanese species with Acer maximowiczii from China. Focus – A. maximowiczianum versus A. maximowiczii, with the latter only found in China, and named by botanist Ferdinand Pax. To add to potential confusion, the literature (such as Hillier and De Beaulieu) either does not acknowledge Acer maximowiczii at all, or subserves it to Acer pectinatum subsp. maximowiczii. Yikes! – that's trouble; but visualize the zianum as a Trifoliate and the zii in the Section Macrantha. I have never propagated the zii subspecies, but if I was to I would choose Acer davidii for rootstock I suppose.

Acer maximowiczii

Perhaps a reason that certain maple species remain in obscurity is due to their tedious, hard-to-pronounce names, and the additional confusion with similar names for very different plants. It was daunting for me at the beginning of my career. Zianum was introduced in 1881 when seeds were imported by Veitch Nursery, after found by Maries in the forests of Hokkaido. Zii was described in 1889, eight years later, then introduced by E.H. Wilson (as number W 4100) which he considered to be Acer laxiflorum. I've never grown Acer maximowiczii by whatever name, and probably my crew would mix it up with the very similar-looking Acer tschonoskii anyway.

Acer pycnanthum at Flora Farm

It's not surprising that Acer pycnanthum is in the Section Rubra, especially since it's nearly identical to the American species Acer rubrum. In the West we know A. pycnanthum as the “Japanese red maple,” while the Nihonjin know it as Hana kaede (“flower maple”) or Hana no ki (“flower of tree”). The specific epithet pycnanthum is pedestrian, meaning “having flowers in dense clusters,” which, yes, I guess it does, but rather weak grounds upon which to bestow a specific epithet. The naming was executed by a little-known German botanist, Karl Heinrich Koch (1809-1879) who was the first professional horticultural officer in Germany. Koch conducted research in southern Russia and the Caucasus Mountains and Asia Minor, so I'm not sure why he latched on to the rare Japanese maple that thrives in swamps and which is limited to a very narrow range in the Nagano region of Honshu, Japan's main island.

Acer pycnanthum

I had already collected Acer pycnanthum before I met my Japanese wife, a gifted woman who graduated from the University of Tokyo's School of Agriculture in Landscape Architecture. Haruko was delighted to see Hana no ki in my Oregon arboretum, and its inclusion probably cemented my credentials to be a suitable marriage partner. It turned out that an impressive specimen of Acer pycnanthum was growing on campus, and, due to its rarity – maybe more than its beauty – it was considered a favorite tree by Haruko's stern “old-school” professor. Haruko was correct that it would be a question on her tree-identity exam...which she aced.

Charles Maries

Acer rufinerve

Acer rufinerve is common in Japan and was first described by Siebold and Zuccarini in 1845. It is another species introduced to English cultivation (in 1879) by Charles Maries, the collector working for Veitch Nursery. Maries had a good year in 1879, and as we saw from last week's Maple Species from Japan (Part 1) he also introduced Acer carpinifolium and Acer crataegifolium in that year. Acer rufinerve's name was derived from Latin rufus, meaning “russet red” due to reddish hair on the leaves and seeds. It is in the Section Macrantha, and typical for members in that group the trunk features vertical gray-white markings on the green bark. I grew a few cultivars of the species but I had to accept that A. rufinerve would never be in much demand, at least from my nursery. The foliage is large and gross compared to the more refined and delicate Acer palmatum, which is why I answered J.D. Vertrees's question about if I had any interest in “species” maples, “Not particularly.” I've changed my mind since then, and rufinerve's outstanding autumn colour is a strong reason why.

Acer rufinerve 'Albolimbatum

Acer rufinerve 'Hatsuyuki'

Acer rufinerve 'Erythrocladum'

I collected a couple of cultivars of Acer rufinerve, 'Albolimbatum' and 'Hatsuyuki' and I dutifully kept them separate even though they always looked the same. The former name is popular in Europe but I find it rather mechanical, and when I discovered that 'Hatsuyuki' was a synonym, I went with the more poetic Japanese name which translates to “first snow.” I also grew the selection 'Erythrocladum' which displays orange bark in winter. Naturally my crew was befuddled with the name because we also grew Acer pensylvanicum 'Erythrocladum' whose bark turns reddish in winter. The Latin name means “clad in red,” but the rufinerve selection was not as strongly clad as its American counterpart, so I discontinued propagating the former, content to keep just one specimen along the main road into Flora Farm. I drove past it a couple of times every day so I was able to constantly monitor it. Sadly, it went into a steady decline, and our annual 100F temperatures didn't do it any good. I put up with it for a dozen years, then improved the overall landscape by editing it altogether. All that remains is the photo above, and the same photo was used in Vertrees's Japanese Maples (2009), Timber Press, page 317.

Acer diabolicum at Hemelrijk, Belgium

Acer diabolicum is about as obscure as a maple can get, and though I knew of it in the literature, the first time I actually saw a tree was at a Maple Society tour in Hemelrijk in 2011 in Belgium. That was in late October and the maple was done for the year, and if there was any seed present I don't remember. It was named by Blume ex Koch in 1864, then introduced by Maries in 1880. The “Horned maple” or “Devil's maple” received its hell-of-a-name due to two devilish horn projections on the seed – a nomenclatural (epithetic) stretch if you ask me.

Acer cissifolium

Acer cissifolium, in the Section Negundo, has leaves like Cissus, the “Grape ivy,” and it forms a small deciduous tree, usually as broad as tall. Another Japanese maple described by Siebold and Zuccarini from Japan, it is hardy to -20F, USDA zone 5. Interestingly, the species is dioecious, meaning that male and female reproductive parts are borne in separate trees...well, except in the absence of nearby “male” pollinator, and then the “female” trees will develop parthenocarpic fruit. It is an interesting species, worthy of inclusion in an arboretum or serious maple collection, but one that'll likely never be found in modern landscapes. As I supposed at the beginning of this two-part Japanese maple review, there are probably species that you have never seen. But I have, and so could you if you are seriously inclined.

Acer capillipes

Charles Sprague Sargent

Maximowicz named Acer capillipes in 1867 for its thin, hair-like samara stalks, then Charles Sprague Sargent of the Arnold Arboretum in Boston, Massachusetts, introduced it in 1892 (from southern Japan) to America and Europe. It grows with a dense, wide-spreading canopy, and the trunk can be interesting with white vertical striations on reddish-brown-green bark. Obviously the serious maple enthusiast will want to collect this species, but the average gardener will have no use for it due to its wide crown, but I appreciate the red new leaves and the bright red petioles. I devoted about 15 years to support an Acer capillipes in my collection – about 5 more years than with my ex-wife – but ultimately I tossed them both, or maybe it was they who tossed me; in any case neither of them remain in my sphere.

Acer argutum

Maximowicz, ever busy, also described Acer argutum (in 1867), then again it was Maries (in 1881) who introduced it to Europe. In the Section Glabra, along with the west-coast American species Acer glabrum, A. argutum is a small shrubby tree which will eventually develop a broad canopy. The specific epithet is from Latin argutus, which has nothing to do with disagreements, but rather refers to the leaf margins being sharp toothed. Hardy to -30F, USDA zone 4, the species should be more available perhaps, but I've never seen a single tree used in an American landscape nor in any garden center. Since it grows with an erect habit, you would expect to find it used as a street tree, or at least as a hybrid with another species that the public would find more exciting. Another ornamental feature is its winter interest with prominent red buds; also, when viewed from a distance, one immediately notices the glowing red young branches, somewhat like the well-known Acer palmatum 'Sango kaku'. On older specimens the small samaras are attractively purple-red, but the one time I sowed the seed I got 100%...total failure that is; but what would have been a greater problem was if they had all germinated, then to whom would I market them all?

Acer campestre 'Carnival' grafted atop Acer miyabei trunk

Kingo Miyabe

Acer miyabei

Carl Maximowicz was present for Acer miyabei, and he described the maple in 1888 and named it for Japanese botanist Kingo Miyabe (1860-1951). It is in the Section Platanoidea along Acers cappadocicum, longipes, truncatum, and, of course platanoides. The bark and leaves look practically identical to Acer campestre which is also in the Section Platanoidea. I purchased my start of A. miyabei from Heritage Seedlings, Oregon, a company that specializes in unusual deciduous species. Spurred by owner Mark Krautmann's enthusiasm, I quote from his previous catalog: “Hardier than Acer campestre, to which it is most often compared, but of more appealing form and therefore requiring less pruning in cultivation. Lacks the invasive character and obtrusive size of Acer platanoides. Very hard to find, it is an excellent urban tree.” Unfortunately it took forever to sell the few I had, and finally with only two left at large size I top-grafted each with a dozen scions of Acer campestre 'Carnival', one of which is planted near the nursery entrance, now an impressive variegated umbrella. That took care of the couple of trees that I couldn't sell, but now, a dozen years later, I regret that I didn't keep A. miyabei in the collection, except for the 5-foot trunk that remains.

Acer distylum

A final species I'll discuss is Acer distylum, one which appears very un-maple-like. It is known as the Linden (Tilia)-leaf maple and is yet another to be described by Siebold and Zuccarini (1845), then introduced by Charles Maries in 1879. Acer distylum's specific epithet refers to two styles – the middle part of the pistil, located between the ovary and stigma. If that's not explanation enough, a high-school botany text will illustrate the plant parts for you.

Acer palmatum

Acer japonicum

Acer shirasawanum

Thus concludes my two-part Maple Species from Japan, and hopefully the reader found my descriptions and trivia to be of interest; fortunately there won't be a final exam because I doubt that I'd do well on it myself. Yes, I presented a number of obscure species, at least from a commercial point of view, and probably you can see why Japan's “Big Three” – Acers palmatum, japonicum and shirasawanum – have made up 95% of my career's maple sales. Nevertheless, what interests me most are the botanists and plant explorers involved in the species' introductions to cultivation. Without them, all of the trees would eventually have been discovered and described anyway, but we moderns must celebrate those who did it first.

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Friday, October 7, 2022

Maple Species from Japan (Part 2)

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