榆属

榆树
	; 榆属特征
科学分类
域：	真核域 Eukarya;
界：	植物界 Plantae;
门：	被子植物门 Magnoliophyta;
纲：	双子叶植物纲 Magnoliopsida;
目：	蔷薇目(Rosales);
科：	榆科(Ulmaceae);
属：	榆属(Ulmus);
二名法
	Carolus Linnaenus; (L.) Batsch

榆树，乔本的一种，双子叶植物中属榆科，主要在北半球的温带地区生长。一般高约25米，树皮粗糙。具高度实用、药用及食用价值。

榆树的叶呈椭圆形或椭圆状波针形，叶长2-8厘米、宽1.5-2.5厘米，两面叶面无毛，或背面脉腋有毛。叶侧脉有9-16对，叶缘有单锯齿，很少有重锯齿。叶柄长约2-10毫米。

榆树在早春发叶前先开花，花呈簇状生成聚伞花序，花被钟形，开4-5花瓣，每朵花有雄蕊约4-5条。翅果近圆形或宽倒卵形，长约1.3-1.5厘米，果皮表面无毛，顶端凹缺。内藏种子，近翅果中部，很少接近凹缺处；果柄长约2毫米。

品种

由于各种榆树易于杂交，有些地区以人工方式繁殖了很多特别的品种，使榆树品种的界定变得较为困难。一般来讲，榆树可分为约20-45个品种，视乎其界定方法之异同。

分类

主要有美国榆树、中国榆树和西伯利亚榆树等品种。

"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.

种植

榆树是一种温带植物，生命力强，较为耐寒，适合于肥沃的沙壤土上生长，生长速度快。榆树为中国北方重要绿化树木，亦常见于民居村落前后。亦可培植成盆景。

榆树花期约在3月上旬，果熟期在4月上旬。

榆树成熟果实可随采随播，亦可使用播种法或插枝法等人工繁殖方法栽种。

荷兰榆树病

荷兰榆树病曾经广泛摧毁全欧洲及北美洲的榆树。这植物疾病的致病原是一种叫做(Ophiostoma nova-ulmi)的霉菌。透过两种生活在榆树树干的榆小蠹作媒介传播。霉菌被媒介带进榆树表面的伤口，再进入树干输送水份营养往树叶和树端的筛管内繁殖。受感染的榆树能在短短3个星期之内被切断其水份传输系统，导致死亡。有研究显示，亚洲品种的榆树有抗致病霉菌的基因。

用途

木材

榆树木材有连续相扣的木纹，品质坚直，可供建房、制家具及农具使用。在西方，榆木亦用来制作棺材。

食用价值

榆树的嫩果和幼叶可以食用或作饲料。有文献记载，在19世纪中期挪威大饥荒时，挪威农民以水煮熟榆树树干来充饥。

药用价值

果、树皮和叶可入药。例如中医药材榆白皮是由榆树干燥树皮或根皮之韧皮部制成，有主治大小便不通，五淋肿满、疥癣、痈肿和滑胎之作用。

其他用途

坚韧的榆树皮可以制成绳索。

榆树也是抗有毒气体如二氧化碳及氯气的树种。其内含beta-固淄醇、植物醇、豆淄醇等多种淄醇及韖质、树胶及脂肪油。

在中世纪时代的欧洲，榆木被制成水管，榆木水管在长期湿润的情况下亦不会腐化。

榆树迁播史

自18世纪至20世纪早期，榆树在欧洲和北美洲被广泛种植，作为街道装饰树种。由于榆树树干高，树冠伸展阔，可以形成一列“榆树隧道”的感觉。

在欧洲，无毛榆 (Wych Elm，即U. glabra)和欧洲光叶榆 (Smooth-leaved Elm，即U. minor)都是这些被广植的品种，其中无毛榆常见于北欧斯堪的那维亚半岛地区、英国北部，而滑叶榆则常见于较南的地区。而因该两种榆树品种自然杂交而生的荷兰榆树 (Dutch Elm，即U. × hollandica)亦常见于欧洲。

北美洲常见的榆树品种称为美洲榆树 (American Elm，即U. americana)，拥有生长速度快，对不同气候和土壤适应力强，坚直的树干能经受强风吹袭，及树型瓶状不用时常修剪的优点，故成为街道装饰树种的首选。现存生长在纽约市华盛顿广场公园西北角的“吊人榆”(Hangman's Elm)，是一棵估计约在1679年开始生长的古老英格兰榆树(English Elm)。

自1850年至1920年间，最知名的榆树品种为苏格兰榆树 (Camperdown Elm，即U. Camperdownii)，为一种经培育变种而来的“变种无毛榆”嫁接到纯种无毛榆的树干而成，其树型被改造成类似喷泉状，在当时的大花园里都采用这种榆树品种作装饰树种。

在20世纪，英国殖民者开发澳大利亚，他们带了大量英格兰榆(English Elm，即U. minor var. vulgaris)的树苗到那里种植，这些“外来”品种在澳大利亚落地生根，并由于地缘关系，避过了曾经在欧洲发生的荷兰榆树病。现在墨尔本的街道仍能发现英格兰榆树巍然屹立。

榆树与周恩来

榆树的耐寒和生命力强的特征，曾被已故中华人民共和国总理周恩来先生提及过。在1973年随墨西哥前总统访问中国的墨西哥庄园园主堂胡安将周恩来派人送来的7根榆树插条运往其庄园种植，其后榆树成林。在2006年园主后人为此设立“周恩来榆树林荫道”，并在内立碑纪念该事迹。说明：立碑纪念该事的不是已死的原主人，而是中共五家中央级新闻单位。等于是中共自己花钱给自己树碑。如此而已。

本来，墨西哥不缺榆树，为什么种植中国的榆树，而不是从余钱种子开始，大有学问。

外部链接

榆树, Yushu 药用植物图像数据库 (香港浸会大学中医药学院) （繁体中文）（英文）