榆树
维基百科，自由的百科全书
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| Carolus Linnaenus (L.) Batsch |
榆樹，喬本的一種，雙子葉植物中屬榆科，主要在北半球的溫帶地區生長。一般高約25米，樹皮粗糙。具高度實用﹑葯用及食用價值。
榆樹的葉呈橢圓形或橢圓狀波針形，葉長2-8厘米﹑寬1.5-2.5厘米，兩面葉面無毛，或背面脈腋有毛。葉側脈有9-16對，葉緣有單鋸齒，很少有重鋸齒。葉柄長約2-10毫米。
榆樹在早春發葉前先開花，花呈簇狀生成聚傘花序，花被鐘形，開4-5花瓣，每朵花有雄蕊約4-5條。翅果近圓形或寬倒卵形，長約1.3-1.5厘米，果皮表面無毛，頂端凹缺。內藏種子，近翅果中部，很少接近凹缺處；果柄長約2毫米。
目录 |
[编辑] 品種
由於各榆樹品種雜交容易，有些地區以人工繁殖了很多特別的品種，而界定榆樹品種較困難，故此榆樹可分為約20-45個品種，視乎界定方法。
[编辑] 分類
主要有美國榆樹﹑中國榆樹和西伯利亞榆樹等品種。
- "Mountain elms": spring flowering; flowers subsessile; leaves very rough above.
- Ulmus bergmanniana. Eastern Asia. <26m tall, with large leaves up to 16cm long and 8cm wide. Very closely related to U. glabra.
- Ulmus castaneifolia. China. <20m tall, with slender stem <50cm in diameter and thick, corky bark. Leaves <15cm long, 6cm wide, densely hirsute when young.
- Ulmus changii. China. <20m tall, with smooth, glabrous, ovate leaves up to 11cm long.
- Ulmus elongata. China. <30m tall, stem <80cm in diameter with exfoliating bark. Long, elliptic leaves <19cm and distinctive shuttle-shaped samaras.
- Ulmus gaussennii. China. <25m tall, with black to very dark grey scabrous bark. Leaves <11cm long, densely pubescent when young.
- Ulmus glabra - Wych Elm. Europe, Asia. Popular cultivars include 'Exoniensis' [Exeter Elm], 'Camperdownii', 'Nana'.
- Ulmus glaucescens. Northern China. <18m tall, with exfoliating, mottled bark. Small, usually ovate leaves <5cm long. Exceptional resistance to drought, but intolerant of wet soils.
- Ulmus laciniata - Manchurian Elm. Eastern Asia. <27m tall and slender stem <50cm in diameter. Distinctive laciniate, often obtriangular leaves <18cm long, with up to seven apical lobes. Closely related to U. glabra, it only grows well in sheltered, humid valleys.
- Ulmus lamellosa. China. <12m tall, with rounded crown and slender trunk with mottled, flaking bark. Good resistance to Dutch elm disease and leaf beetles, but intolerant of wet soils.
- Ulmus macrocarpa. Northeastern Asia. <12m tall, with thick, leathery obovate leaves <9cm long. Very large sub-orbicular samaras <47mm long and <39mm wide. Demands well-drained soil. Good resistance to Dutch elm disease.
- Ulmus microcarpa. China (Xizang {:Tibet} only). <30m tall, with stem <80cm in diameter. Large, glabrous leaves <17cm long, but very small samaras <8mm in diameter.
- Ulmus prunifolia. China. <30m tall, slender stem <45cm in diameter with smooth dark grey bark. Narrow, glabrescent leaves <11 cm long.
- Ulmus rubra - Slippery Elm or Red Elm. Eastern North America.
- Ulmus uyematsui. Taiwan. <25m tall with dark grey bark exfoliating in irregular flakes. Leaves elliptic, < 11cm long.
- Ulmus wallichiana - Himalayan Elm or Kashmir Elm. Northern Afghanistan, northern Pakistan, western Himalaya.
- "Field elms": spring flowering; flowers subsessile; leaves usually smooth above.
- Ulmus chenmoui. China. <20m tall, with exfoliating bark and broad, obovate leaves <18cm long.
- Ulmus chumlia. Himalaya. <25m tall, with spreading crown and sinuous branches. Leaves narrowly obovate, <10cm long and <4cm wide.
- Ulmus davidiana - North-east Asia, inc. Japan. <15m tall, leaves obovate <10cm long by 5.5cm broad. Two varieties recognized by Fu:
- Ulmus davidiana var. davidiana - David Elm. China. <12m tall, vase-shaped. Intolerant of exposed conditions and wet soils.
- Ulmus davidiana var. japonica - Japanese Elm. North-east Asia, inc. Japan. 'Discovery', 'Freedom', 'Jacan', 'Mitsui Centennial', and 'Thomson' are hardy varieties selected for planting in Canada in the 1980s.
- Ulmus harbinensis. China (Heilongjiang only). <15m tall; leaves <5.5cm long and <3.5cm broad.
- Ulmus lanceaefolia. Western China (Yunnan only), India (Darjeeling area), Bhutan, Sikkim, Bangladesh, Laos, Myanmar. A very large tree, <45m tall, with spreading crown. The bark of the trunk exfoliates in small scales. Oblong to elliptic leaves, <8cm long and <2.5cm wide. Evergreen in the southern part of its range.
- Ulmus minor - Field Elm. Europe. Numerous sub-species, varieties including:
- Ulmus minor subsp. angustifolia. syn. var. cornubiensis - Cornish Elm. England, France; local endemic.
- Ulmus minor subsp. minor - Smooth-leaved Elm. Europe; syn. U. carpinifolia. Disease-resistant cultivars: 'Christine Buisman', released in 1936, and 'Bea Schwarz' in 1948.
- Ulmus minor var. plotii - Locks Elm. England; local endemic.
- Ulmus minor 'Sarniensis' - Jersey Elm or Wheatley Elm, Guernsey Elm, Southampton Elm. Channel Islands, France; local endemic, widely cultivated in Britain.
- Ulmus minor var. vulgaris - English Elm. England, Italy, Spain. Syn. U. procera. Also known as the 'Atinian Elm'.
- Ulmus pseudopropinqua. Northern China (Inner Mongolia). <10m tall with corky branches. Good resistance to Dutch elm disease and elm beetles.
- Ulmus pumila - Siberian Elm. China, India (Kashmir), Siberia. American cultivars include 'Dropmore', 'Park Royal', 'Lincoln' and 'Chinkota'.
- Ulmus szechuanica. China. <18m tall, with umbrella-like canopy. Leaves obovate, glabrescent, <9cm long, dark red on emergence, and again in autumn.
- Ulmus villosa - Cherry Bark Elm. India (Kashmir). <25m tall, with broad crown <14m wide and pendulous branches. Leaves oblong-elliptic acute <11cm long and <4cm broad. A long-lived species, sacred specimens planted around temples are over 800 years old.
- Ulmus wilsoniana - Wilson's Elm. Western China. Now treated as conspecific with U. davidiana by Fu. 'Prospector' is a U. S. National Arboretum selection, vase-shaped and growing to 12m tall, with deep-green glabrous leaves resistant to elm leaf beetle.
- "White elms": spring flowering; flowers pedunculate
- Ulmus alata - Winged Elm. Eastern North America.
- Ulmus americana - American Elm. North America east of the Rockies. Cultivars with resistance to Dutch elm disease include: 'American Liberty', 'Brandon', 'Delaware', 'Independence', 'Jefferson', 'New Harmony', 'Princeton', 'Valley Forge' and 'Washington'.
- Ulmus androssowii - Narwan Elm. China (Yunnan, Sichuan, and Xijang {Tibet}). <20m tall, with ovate or elliptic glabrous leaves <8cm long and <2.5cm wide.
- Ulmus laevis - European White Elm or Fluttering Elm, Spreading Elm, (USA only) Russian Elm. Eastern Europe, Western Asia.
- Ulmus thomasii - Rock Elm. Eastern North America.
- "Autumn-flowering elms": autumn flowering.
- Ulmus crassifolia - Cedar Elm. Eastern North America.
- Ulmus parvifolia - Chinese Elm or Lacebark Elm. China. 27 known American cultivars including: 'A. Ross Central Park' (Central Park Splendor™), 'Bosque', 'Drake', 'Dynasty', 'Emer I' (Athena™), 'Emer II' (Allee™), 'King's Choice', 'Ohio', 'Pathfinder', 'Sempervirens'. Many others such as 'Hokkaido' are miniatures raised for bonsai.
- Ulmus serotina - September Elm. Eastern North America.
- Ulmus tonkinensis. Western China, Northern Vietnam. Evergreen tree with exfoliating bark. Ovate-lanceolate glabrous leaves <10cm long and <3cm wide.
- Hybrids and hybrid origin cultivars.
- Ulmus × brandisiana. U. chumlia × U. wallichiana. Naturally-occurring hybrid in Pakistan and north-west India.
- Ulmus × elegantissima 'Jacqueline Hillier'. English hybrid of uncertain parentage, possibly U. glabra × U. minor var. plotii.
- Ulmus × hollandica - Dutch Elm. U. glabra × U. minor.
- Ulmus 'Cathedral'. U. pumila × U. davidiana var. japonica. American hybrid, more closely resembling its male parent, U. davidiana var. japonica than its siblings 'New Horizon' and 'Sapporo Autumn Gold' but not as resistant to Dutch elm disease.
- Ulmus 'Clusius'. (U. glabra Exoniensis × U. wallichiana) × U. × hollandica 'Bea Schwarz'. Dutch hybrid released 1983. Similar to 'Lobel', but with slightly improved resistance to Dutch elm disease.
- Ulmus 'Columella'. 'Plantyn' or 'Plantijn' selfed. Dutch hybrid released 1989.
- Ulmus 'Commelin'. U. × hollandica 'Vegeta' × U. minor. Dutch hybrid released 1960. Fast growing, but only moderate resistance to disease and wind damage.
- Ulmus 'Coolshade'. U. rubra × U. pumila.
- Ulmus 'Dodoens'. U. glabra × U. wallichiana selfed. Dutch hybrid released 1973. Strong, fast growing, but only moderately resistant to Dutch elm disease.
- Ulmus 'Frontier'. U. minor × U. parvifolia. <13m tall, with glabrous leaves turning dark red in autumn.
- Ulmus 'Green King'. U. rubra × U. pumila.
- Ulmus 'Groeneveld'. U. minor × U. glabra. Dutch hybrid released 1960. Slower growing than 'Commelin', and only moderately resistant to disease. Planted mostly in Dutch towns.
- Ulmus 'Homestead'. U. pumila × ((U. hollandica 'Vegeta' × U. minor) × (U. pumila × U. minor)). U. S. National Arboretum hybrid. Fast growing, producing a pyramidal crown, and well-suited to city conditions. High resistance to Dutch elm disease.
- Ulmus 'Lobel'. (U. glabra Exoniensis × U. wallichiana) × U. × hollandica 'Bea Schwarz'. Dutch hybrid released 1973. Fastigiate, small-crowned, small-leaved tree resistant to sea winds, but only moderately resistant to Dutch elm disease.
- Ulmus 'Morton' (Accolade ™). U. davidiana var. japonica × U. wilsoniana. American hybrid >30m tall, vase-shaped tree with small, glossy, dark-green leaves. Highly resistant to Dutch elm disease, but not available in Europe.
- Ulmus 'Morton Glossy' (Triumph ™). 'Morton' × 'Vanguard'. <20m tall, with upright oval- to vase-shape, and dark green glabrous leaves.
- Ulmus 'Morton Plainsman' (Vanguard ™). U. pumila × U. japonica. American hybrid <15m tall, with rounded crown. Drought resistant.
- Ulmus 'Morton Red Tip' (Danada Charm ™). U. davidiana var. japonica × U. wilsoniana. <25m tall, vase-shaped with arching limbs, and dark green leaves. A seedling of (Accolade ™).
- Ulmus 'Morton Stalwart' (Commendation ™). (U. davidiana var. japonica × U. wilsoniana) × (U. pumila × U. minor). <20m tall, with upright, oval shape.
- Ulmus 'Nanguen' (Lutèce ™). 'Plantyn' × (U. × hollandica 'Bea Schwarz' × U. × hollandica 'Bea Schwarz' selfed). Dutch hybrid, released 2002. [1].
- Ulmus 'New Horizon'. U. davidiana var. japonica × U. pumila. American hybrid now also grown under licence in Germany. Very resistant to Dutch elm disease, but unsuited to poorly-drained ground.
- Ulmus 'Patriot'. 'Urban' × U. wilsoniana 'Prospector'. American hybrid with vase-shaped crown. High resistance to Dutch elm disease and elm yellows. Very fast growing, capable of exceeding 1m per annum.
- Ulmus 'Pioneer'. U. glabra × U. minor. U. S. National Arboretum hybrid. Dense, spherical crown. Only moderately resistant to Dutch elm disease.
- Ulmus 'Plantyn' or 'Plantijn'. (U. glabra Exoniensis × U. wallichiana) × (U. minor × U. minor). Dutch hybrid released 1973. Fast growing with broad crown. Tolerant of sea winds, but only moderately resistant to Dutch elm disease.
- Ulmus 'Plinio'. 'Plantyn' × U. pumila. Italian hybrid released 2003.
- Ulmus 'Regal'. U. pumila × ((U. hollandica 'Vegeta' × U. minor) × (U. pumila × U. minor)). American hybrid with upright columnar form making it suitable for urban planting. High resistance to Dutch elm disease.
- Ulmus 'San Zanobi'. 'Plantyn' × U. pumila. Italian hybrid released 2003.
- Ulmus 'Sapporo Autumn Gold'. U. davidiana var. japonica × U. pumila. From a chance crossing in Sapporo, Japan. Grows quickly to form dense vase-shaped crown, although young trees need pruning to produce clean stem. Highly resistant to Dutch elm disease, and now also widely available in Europe.
- Ulmus 'Urban'. (U. × hollandica 'Vegeta' × U. minor) × U. pumila. U. S. National Arboretum hybrid.
- Ulmus 'Vegeta' - Huntingdon Elm, syn. Chichester Elm. U. glabra × U. minor selfed. Old English hybrid raised circa 1750.
- Ulmus 'Wredei' - Golden Elm. U. × hollandica cultivar.
- and many more without formal hybrid names
The other genera in the Ulmaceae are Zelkova (Zelkova) and Planera (Water-elm). Celtis (Hackberry or Nettle Tree), formerly included in Ulmaceae, is now treated in the family Cannabaceae.
[编辑] 種植
榆樹是一種溫帶植物，生命力強，較為耐寒，適合於肥沃的沙壤土上生長，生長速度快。榆樹為中國北方重要綠化樹木，亦常見於民居村落前後。
榆樹花期約在3月上旬，果熟期在4月上旬。
榆樹成熟果實可隨採隨播，亦可使用播種法或插枝法等人工繁殖方法。
[编辑] 荷蘭榆樹病
荷蘭榆樹病曾經廣泛摧毀全歐洲及北美洲的榆樹。這植物疾病的致病原是一種叫做(Ophiostoma nova-ulmi)的霉菌。透過兩種生活在榆樹樹幹的榆小蠹作媒介傳播。霉菌被媒介帶進榆樹表面的傷口，再進入樹幹輸送水份營養往樹葉和樹端的篩管內繁殖。受感染的榆樹能在短短3個星期之內被切斷其的水份傳輸系統，導致死亡。有研究顯示，亞洲品種的榆樹有抗致病霉菌的基因。
[编辑] 用途
[编辑] 木材
榆樹木材有連續相扣的木紋，品質堅直，可供建房﹑製傢俬及農具使用。在西方，榆木亦作棺材的材料。
[编辑] 食用價值
榆樹的嫩果和幼葉可作食用或作飼料。有文獻記載，在19世紀中期挪威大饑荒時，挪威農民以水灼熟榆樹樹幹來充饑。
[编辑] 葯用價值
果﹑樹皮和葉可入葯。例如中醫葯材榆白皮是由榆樹乾燥樹皮或根皮之韌皮部製成，有主治大小二便不通，五淋腫滿﹑疥癬﹑癰腫和滑胎之效。
[编辑] 其他
堅韌的榆樹皮可以製成繩索。
榆樹也是抗有毒氣體如二氧化碳及氯氣的樹種。其內含beta-固淄醇﹑植物醇﹑豆淄醇等多種淄醇及韖質﹑樹膠及脂肪油。
在中世紀時代的歐洲，榆木被製成水管，榆木水管可以在長期濕潤的情況下亦不會腐化。
[编辑] 榆樹遷播史
自18世紀至20世紀早期，榆樹在歐洲和北美洲被廣泛種植，作為街道裝飾樹種。由於榆樹樹幹高，樹冠伸展闊，可以凝造一列「榆樹隧道」的感覺。
在歐洲，無毛榆 (Wych Elm，即U. glabra)和歐洲光葉榆 (Smooth-leaved Elm，即U. minor)都是這些被廣植的品種，其中無毛榆常見於北歐斯堪的那維亞半島地區﹑英國北部，而滑葉榆則常見於較南的地區。而因該兩種榆樹品種自然雜交而生的荷蘭榆樹 (Dutch Elm，即U. × hollandica)亦在歐洲常見。
北美洲常見的榆樹品種稱為美洲榆樹 (American Elm，即U. americana)，擁有生長速度快，對不同氣候和土壤適應力強，堅直的樹幹能抵受強風吹襲，及樹型瓶狀不用時常修剪的優點，故成為街道裝飾樹種的首選。現存生長在紐約市華盛頓廣場公園西北角的「吊人榆」(Hangman's Elm)，是一棵估計約在1679年開始生長的古老英格蘭榆樹(English Elm)。
自1850年至1920年間，最知名的榆樹品種為蘇格蘭榆樹 (Camperdown Elm，即U. Camperdownii)，為接一種經培育變種而來的「變種無毛榆」接枝到純種無毛榆的樹幹而成的，其樹型被改造成類似噴泉狀，在那時代的大花園都有採用這種榆樹品種作裝飾樹種。
在20世紀英國殖民者開發澳大利亞，他們帶了大量英格蘭榆(English Elm，即U. minor var. vulgaris)的樹苗到這裡種植，這些「外來」品種在澳大利亞落地生根，並由於地緣關係，避過了曾經在歐洲發生的荷蘭榆樹病。現時在墨爾本的街道仍然發現英格蘭榆樹屹立。
[编辑] 榆樹與周恩來
榆樹的耐寒和生命力強的特徵，曾被已故中華人民共和國總理周恩來先生提及過。在1973年隨前墨西哥前總統訪問中國的墨西哥莊園園主堂胡安將周恩來派人送來的7根榆樹插條運往其莊園種植，其後榆樹成林。在2006年園主後人為此設立「周恩來榆樹林蔭道」，並在內立碑紀念該事跡。
