Friday, December 6, 2013

Shedding Light on the Obscure

Today we'll examine some obscure* tree species, perhaps some that you know little or nothing about. Don't groan and decide that you'll be bored, for all the trees I will feature display ornamental characteristics. Maybe your largest challenge is to learn how to pronounce them, then try to remember the names a day or two later. I guarantee that if you allow these species into your floral world, whether by planting, or via armchair gardening, you will receive your reward.

*The word obscure originated in Middle English between 1350 and 1400 and was derived from Old French oscur or obscur, and that derived from Latin obscurus for "dark."

Euptelea pleiosperma

Euptelea polyandra

Euptelea pleiosperma, from the eastern Himalaya and western China, was introduced over one hundred years ago, but I challenge you to find even one in an American landscape or public park. It is a small, often multi-trunked tree or large bush with attractive copper-red new growth. Reddish flowers are "witch hazel"-like and appear in clusters along the leafless branches, and consist of anthered stamens. In autumn the green leaves change to yellow and red. The Greek-derived species name pleio refers to "full of" or "many," and sperma is Late Latin, from Greek speirein, meaning "to sow," and the flowers are wind pollinated. The genetic name Euptelea is derived from Greek eu for "well" or "handsome" and ptelea for the appearance of the fruits resembling an "elm." I have a couple in my landscape and only wish I could acquire the second species of the genus, polyandra, which is said to be prettier in the fall landscape, and is native to Japan.

Sorbus commixta

Sorbus commixta

Sorbus alnifolia

Sorbus alnifolia

I am not really a grower of Sorbus, the ashes or "Rowans," but I saw species commixta, a Japanese tree with incredible fall color about twelve years ago at Kew Gardens in London. Since then I have seen it in other European gardens, but for unknown reasons it is still rare in American landscapes. And two years ago I encountered Sorbus alnifolia (alder-leaf) in Belgium at Arboretum Wespelaar. I had never even seen alnifolia before, and subsequent research indicated it too was from Japan. My Wespelaar visit corresponded with sunny weather in October, to a sophisticated collection renowned for maples, Stewartia, oaks etc. Leaves of alnifolia were mostly gone and the multitude of tiny pink berries sparkled like jewels in the afternoon light. This visit was in conjunction with the International Maple Society Symposium, and when all individual attendees regrouped to the visitor center, everyone asked everyone: "Did you see the Sorbus alnifolia?" Later on I discovered that the pink berries would eventually evolve to bright red, but what a dainty little tree! I resolved to acquire alnifolia, and I now even have some for sale at an affordable price.

Sorbus americana

I'll mention one final species of Sorbus that I encountered recently on the Blue Ridge Parkway in North Carolina, Sorbus americana. This species occurred at elevations of four-to-five thousand feet. The trees were small and scrappy, very unornamental in form, but the crop of bright red berries was outstanding. We (my companion Phil and I) collected some seed, which may not have been legal, but what could we do? The trees were leafless at the end of October, and the occasional times when the sun poured through the swirling clouds and gleamed light upon the berries, Phil and I would ooh and aah with amazement. I hope that not too many of the seeds will germinate, as I don't expect any profit from the collection, but it would be fun to have one in the Flora Wonder Arboretum, assuming that it would prosper in my low-elevation climate.

Acer micranthum

Acer micranthum

Acer micranthum is also a tree that is rare in American landscapes, but most undeservedly so. Its name is due to small-sized flowers and the resultant seeds are tiny as well. Acer micranthum also originates from Japan, and was introduced into Europe around 1880, and I feel that any serious Japanese maple collection should contain at least one. The species is at least as hardy as palmatum, and is of smaller stature than many palmatum cultivars. We have propagated micranthum by rooted cuttings under mist in summer, or by grafting onto stripe-bark species such as Acer davidii or Acer tegmentosum. I remember seeing micranthum at Westonbirt in England about ten years ago, on a tour led by Peter Gregory. He introduced us to a nice specimen, and seemed very delighted to show it off, especially the dangling clusters of small pink seed. I know of no cultivars of Acer micranthum except for 'Candelabrum', which originated at Hillier's Arboretum, and is larger than the type due to the likelihood that it is a hybrid.

Acer nipponicum

Acer nipponicum

Acer nipponicum is another obscure maple species from Japan, one I don't see used in America, although the better collections in Europe will have it. The species name is from Nipponicus, from "Nippon," an old name for Japan. Today someone from Japan is referred to as "nihonjin," and any reference to "nip" or "Nippon" is considered derogatory. I like the substantial olive-green leaves with their rugose texture, but they can look ragged after a 100 degree F August day in Oregon (with no humidity). In Japan it is native to the islands of Honshu, Shikoku and Kyushu in mountain forests where it gets plenty humid. I have grown a specimen for twelve years, but it still has not produced seed. Also I have wasted time trying to propagate nipponicum via rooted cuttings; my efforts yielded 100%...dead. I even tried grafting onto Acer pseudoplatanus and other species, with the same result. Some years nipponicum foliage turns to yellow in autumn, in others it can go from green to brown.

Berberis temolaica

Berberis temolaica should not be dismissed as, "Shit, another thorny barberry," a plant that no prudent gardener would dare attempt. I received my start from a friend, plantsman R. Hatch, a holic who has foisted many unwise species upon me, though I too have afflicted many upon him. Temolaica is not such a plant, however. From dry-land Tibet, it is a vicious bitch to handle, but the soft blue-green new growth in spring changes to powder-blue by summer. This species was introduced by Frank Kingdon-Ward (of great Rhododendron fame) in 1924. I had a nice plant in the Short Road – eight feet tall by three feet wide in ten years – but I sold it to a high-bidder for good profit. But yikes, my temolaica offspring perished in an unheated greenhouse a few years later, and even though the species is listed as hardy to USDA zone 5, I lost the lot. Friend Roger Gossler, who probably got his stock from me...bailed me out a year ago, so now I grow it again. Generosity – which Gossler excels at – often leads to self-preservation, and I suggest that a visit to would lead you to many wonderful plants from his mail-order nursery. Please revisit my Gossler Farms tour from 4/12/13, but of course finish this blog first. I also encourage you to purchase Gossler's book, Best Hardy Shrubs, which relates his personal encounters with outstanding trees and shrubs.

Stewartia koreana

Stewartia koreana

So now is a good time to introduce Stewartia koreana, a seldom-encountered species that rivals any in the exquisite genus. From Korea, of course, it is a small-to-medium size tree with superb colorful bark. E.H. Wilson introduced this wonderful tree in 1917, and it is similar to species pseudocamellia except for wider, more spreading petals on the flowers. And, the trunk of koreana exceeds pseudocamellia for beauty. I have grown Stewartia koreana for fifteen or so years, but never kept one around long enough to really appreciate the bark. About three years ago I visited Gossler Farms and witnessed brother Eric's garden with a mature specimen, and I was ponderously amazed by the trunk. Also, autumn color is as fantastic as on any deciduous tree. What a joy to have this wealthy Gossler garden within a do-able three-hour drive away.

Catalpa bignonioides 'Nana'

Catalpa bignonioides is the "Indian Bean Tree," a mid-sized eastern American native that flowers in late summer. There exists a golden form – 'Aureum' – and 'Variegata' with creamy-white-variegated leaves, but I only grow the cultivar 'Nana', which forms a small rounded bush. It is a most luxuriant tree with delicious green leaves, and my only cause for concern is that big wet leaves in a summer wind storm can lead to broken branches.

Note  that this "Indian Bean" refers to American natives and not to their Asian relatives. The origin of the name Catalpa is possibly from a Creek (Indian) word katalpa, or is maybe from catawba, where the botanist (Scopoli) incorrectly transcribed the name. You can easily go beyond any of the speculative etymology and just consider C. b. 'Nana' to be a wonderful little tree; certainly one that your neighbors will never grow, but a form that can proudly adorn your garden.

Juniperus coxii

Juniperus coxii in shade
Juniperus coxii from Flora Wonder Arboretum

One of the most graceful of any specimen in the Flora Wonder collection is Juniperus coxii, the "Himalayan Drooping Juniper." It is a conifer that seldom appears on our plant availability because of difficulty in propagation and slow rate of growth, and it can take up to a dozen years before you have anything that looks good. It is popular in the better arboreta of Britain, and most likely the fantastic specimens there were propagated by seed. Originally coxii was collected in northern Burma by E.H.M. Cox and Reginald Farner in 1920. It was once considered a variety of Juniperus recurva and indeed Hillier's Manual of Trees and Shrubs, Fifth Edition, still lists it that way. Debreczy and Racz in Conifers Around the World (2011) report that "recent molecular studies" support coxii's treatment at species rank. In any case the typical recurva shows little horticultural merit, while coxii displays longer and more pendulous branches. Besides the beauty of the jade-green foliage, older specimens feature exfoliating gray-brown trunks, although I have seen a specimen with reddish-brown and less exfoliation, for it was growing in considerable shade. In its native range coxii occurs in upper coniferous zones and is hardy to USDA zone 7, possibly 6.

Juniperus rigida 'Pendula'

Juniperus cedrus

Juniperus pingii

Another outstanding species is Juniperus rigida. We received our start twenty five years ago as rigida 'Pendula', but I'm not positive whether the lax growth habit of the species was inappropriately constituted as a cultivar name, or whether 'Pendula' really is a distinct selection. The species comes from Japan, Korean and northern China, and was introduced into England by J.G. Veitch in 1861. Like Juniperus coxii, rigida is an elegant weeping tree with green foliage and exfoliating bark. Juniperus rigida is commonly known as the "Temple Juniper," while coxii is called the "Coffin Juniper" (for obvious reasons). These two species – along with my favorite juniper of all, Juniperus cedrus (USDA zone 7) – are proof enough that the genus contains some species that are most ornamental, as much as any of the coniferous trees. And I'll add Juniperus pingii onto that list as well.

Picea breweriana

Another "weeping" conifer, Picea breweriana, is of great beauty and I've been interested in it for my entire career. The Hoyt Arboretum in Portland Oregon houses a collection of fifteen or so, planted on a hillside where you can look down at them. They must be nearing fifty years of age, and even non-horticulturalists must be impressed by them. At first the species was considered rare (when it was introduced in 1891), but numerous populations have since been discovered, and I have seen many of them myself.

A mature Picea breweriana with Mt. Shasta

I vividly remember a solo "Brewer's Spruce Trip" I took in southwest Oregon and northern California, where a local Forest Ranger provided me with maps and patted me on the back and wished me well on my noble sojourn. The poor green-shirted bureaucrat acted like he wanted to come along with me, but I usually prefer to go case I want to do something illegal along the way. But the meeting was memorable because it was the only time in my life that a governmental employee had ever considered me worthy of concern and attempted to further my cause. My solo trip was a success, highlighted by a photo of a mature breweriana with Mt. Shasta in the background.

Picea breweriana

When I began the nursery over thirty years ago, I was able to purchase twenty-year-old Picea breweriana seedlings that were eight-to-ten feet tall for $15 apiece. I lined out about thirty of them, and they sat in my field for a few years, never looking very happy. Finally one year we had an unusually wet spring and they died or looked bad enough for me to cut down. All of the other species of Picea in the same field looked great, and I learned that if I wanted to grow breweriana at my nursery, I would have to graft them onto a better rootstock, such as Picea abies. But I've seen wonderful mature specimens in botanic gardens in England and Scotland and wonder how they make it, since most botanic gardens are too snooty to have a "created species" (tops different than the roots) in their collection. In Manual of Trees and Shrubs Hillier writes of breweriana that it is "perhaps the most beautiful of all spruces and one of the most popular of all ornamental conifers." What does Hillier mean by "popular?" No one in England – outside of botanic gardens – grows the species. I think that old Hillier and his plant friends were enthusiastic about breweriana, but that it remains rare in English landscapes. I invite any bona fide Englishman to correct me if I'm wrong.

All plants featured in this blog are worthy of growing, as I said at the beginning. But I would be bankrupt if I depended on you to buy them from me. So, from time to time I go out and visit mine, and leave you your preferences. But thanks for what you do buy.

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