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Dear Station Members,
Attached is a recent local news on the proposed tree planting by the Urban Redevelopment Authority (URA) in Tai Kok Tsui to 're-vitalize' the streetscape in this mature district. It was full of good intention & it proposed to plant tree species in accordance with the name of the street, e.g. Cherry for Cherry Street, Oak for Oak Street, & Pine for Pine Street. It also mentioned that studies would be carried out to check suitability of the species at the location by the designers.
Arboriculture is a scientific discipline. It is known in our profession that Arborist practises more as a scientist rather than an artist. For the above proposal, it would be known that Cheery, Oak & most Pines are temperate species which would have survival problem in our tropical summer. Tai Kok Tsui would come to a temperature of 39C in the hot summer as given by the HK Observatory only a little while ago. Also, these proposed species would mostly come from regions where there is no typhoon. HK is a typhoon country & priority may have to be placed on wind failure rather than 'flowering' or anything else. If not, it may be another case of Mother Nature makes the Rules, not any of us. Just look at the number of tree failures in our territory after rainstorms ...
If Alaska would have a street called Coconut Avenue somewhere, would the developer there choose Coconut as the 'Theme' species to green that street? After all, Alaska is more than temperate during winter time with tons of snow everywhere, having tropical palms there would add warmth & comfort to the residents when they are wearing fur coats. But would fantasies fit realities?
Former ETF carried out a lot of research on introducing foreign species for planting in Southern China. A research paper was published by the Station Manager in China in 2002 & is attached in this Station Mail for general reference.
HK people always give admiration to Singapore greenery especially when it comes to tree planting. This is heard from our local Tree Experts time & time again in community forums & discussions. Nevertheless, how many of us would understand the tree planting in Singapore is masterminded by a leading Govt agency called National Parks Board (Nparks) alone? Nparks have about 600 staff looking after over 1.3 million trees in Singapore & over 20% of Nparks staff are Arborists. Arborists would make the final decision on tree planting in Singapore from design, operation to maintenance & not anybody else, ever since Singapore has become a nation. This may be one of the untold secrets behind their success not known to the HK people.
A Station Mail will come out very soon for anyone interested to join the HK Delegation to visit the Singapore Garden Festival 2008 Expo from July 24 - 26, 2008. ISA HK/China has proposed a day tour to study the Singapore tree planting on Friday July 25 or Sunday July 27 for the delegation & anyone interested to join in. This will let the visitors see with their own eyes how & why Singapore tree planting has become so successful.
Looking forward to anyone joining us to visit the SGF 2008 in July. We already have over 13 going even before the announcement.
best regards,
Sammy Au
Station Manager
The ISA Mission - Through research, technology, and education, promote the professional practice of arboriculture and foster a greater public awareness of the benefits of trees. (http://www.isa-arbor.com/)
Dear Station Members,
Attached is a recent local news on the proposed tree planting by the Urban Redevelopment Authority (URA) in Tai Kok Tsui to 're-vitalize' the streetscape in this mature district. It was full of good intention & it proposed to plant tree species in accordance with the name of the street, e.g. Cherry for Cherry Street, Oak for Oak Street, & Pine for Pine Street. It also mentioned that studies would be carried out to check suitability of the species at the location by the designers.
Arboriculture is a scientific discipline. It is known in our profession that Arborist practises more as a scientist rather than an artist. For the above proposal, it would be known that Cheery, Oak & most Pines are temperate species which would have survival problem in our tropical summer. Tai Kok Tsui would come to a temperature of 39C in the hot summer as given by the HK Observatory only a little while ago. Also, these proposed species would mostly come from regions where there is no typhoon. HK is a typhoon country & priority may have to be placed on wind failure rather than 'flowering' or anything else. If not, it may be another case of Mother Nature makes the Rules, not any of us. Just look at the number of tree failures in our territory after rainstorms ...
If Alaska would have a street called Coconut Avenue somewhere, would the developer there choose Coconut as the 'Theme' species to green that street? After all, Alaska is more than temperate during winter time with tons of snow everywhere, having tropical palms there would add warmth & comfort to the residents when they are wearing fur coats. But would fantasies fit realities?
Former ETF carried out a lot of research on introducing foreign species for planting in Southern China. A research paper was published by the Station Manager in China in 2002 & is attached in this Station Mail for general reference.
HK people always give admiration to Singapore greenery especially when it comes to tree planting. This is heard from our local Tree Experts time & time again in community forums & discussions. Nevertheless, how many of us would understand the tree planting in Singapore is masterminded by a leading Govt agency called National Parks Board (Nparks) alone? Nparks have about 600 staff looking after over 1.3 million trees in Singapore & over 20% of Nparks staff are Arborists. Arborists would make the final decision on tree planting in Singapore from design, operation to maintenance & not anybody else, ever since Singapore has become a nation. This may be one of the untold secrets behind their success not known to the HK people.
A Station Mail will come out very soon for anyone interested to join the HK Delegation to visit the Singapore Garden Festival 2008 Expo from July 24 - 26, 2008. ISA HK/China has proposed a day tour to study the Singapore tree planting on Friday July 25 or Sunday July 27 for the delegation & anyone interested to join in. This will let the visitors see with their own eyes how & why Singapore tree planting has become so successful.
Looking forward to anyone joining us to visit the SGF 2008 in July. We already have over 13 going even before the announcement.
best regards,
Sammy Au
Station Manager
The ISA Mission - Through research, technology, and education, promote the professional practice of arboriculture and foster a greater public awareness of the benefits of trees. (http://www.isa-arbor.com/)
引种的艺术
作者自1995年开始，在广东省广州市花都区建立了占地200亩的引种试产基地，从事引进国内没有或是稀有的花木品种，计有棕榈科、苏铁科、绿化乔木灌木、洋兰类、草花类、鲜切花类、阴
生植物类、仙人掌和多肉植物类等等。算至2003年中，累积已被引种试产的品种已超过1800
种，90%以上是从种子引进，其他的有小苗、插条或成品引进。
总结过去八年时间的引种经验以后，众多的所引品种到今天还在批量生产的占不到全部引进品种总数的3%，个中原因可分为商业考虑和技术设施。本文现只集中讨论作者在引种过程当中所涉及的技术设施问题，不对市场策略方面作出考虑。
作者过去所引进的品种大部份是采取‘异地引种’的手法，也即是并非从中国境内取种，而种苗来自世界各地，当中很多品种来自热带雨林，例如棕榈科；但也有许多来自乾旱沙漠，例如仙人掌科。其中有可耐寒至零下22C的耐寒品种，例如 BUTIA CAPITATA，也有可长时间可耐40C高温的PHOENIX DACTYLIFERA。有长期喜欢泡在水里的RAVENEA RIVULARIS，也有下一
总结过去八年时间的引种经验以后，众多的所引品种到今天还在批量生产的占不到全部引进品种总数的3%，个中原因可分为商业考虑和技术设施。本文现只集中讨论作者在引种过程当中所涉及的技术设施问题，不对市场策略方面作出考虑。
作者过去所引进的品种大部份是采取‘异地引种’的手法，也即是并非从中国境内取种，而种苗来自世界各地，当中很多品种来自热带雨林，例如棕榈科；但也有许多来自乾旱沙漠，例如仙人掌科。其中有可耐寒至零下22C的耐寒品种，例如 BUTIA CAPITATA，也有可长时间可耐40C高温的PHOENIX DACTYLIFERA。有长期喜欢泡在水里的RAVENEA RIVULARIS，也有下一
个晚上大雨就会产生根腐病的YUCCA ROSTRATA。有天天喜欢强烈暴晒的CARNEGIEA GIGANTEA，也有晒上一天就产生日灼症的SPATHIPHYLLUM FLORIBUNDUM。它们其中有的1克重量的种子就超过80,000粒，例如ACHIMENES HYBRIDA，也有1粒种子可达20KG重量，例如LODOICEA MALDIVICA。在引进的种苗当中，有的是从国外苗场购进，也有部份是作
者自己到国外苗场或郊野采摘。
对于大部份所引品种来说，作者经常缺乏文献去追查该品种是如何催芽、育苗和栽培。除了某些商业化品种以外，大部份的引种技术都要靠作者自己研究试探，自我寻找方向。在这不断探索的过程中，作者厘定了一套‘引种八点’作为指南，这八点是光、温、湿、水、肥、植料、病虫害、和风力。作者发觉如果这八点都能够全部符合，则所引品种便能正常茁壮长大；但只要其中任何一点达不到，则那次引种注定失败。
对于大部份所引品种来说，作者经常缺乏文献去追查该品种是如何催芽、育苗和栽培。除了某些商业化品种以外，大部份的引种技术都要靠作者自己研究试探，自我寻找方向。在这不断探索的过程中，作者厘定了一套‘引种八点’作为指南，这八点是光、温、湿、水、肥、植料、病虫害、和风力。作者发觉如果这八点都能够全部符合，则所引品种便能正常茁壮长大；但只要其中任何一点达不到，则那次引种注定失败。
现将此八点作较为详尽讨论如下：
(1) 光
这里涉及的主要是光强、光质和光照时间。每一种植物都有它本身喜欢的光强，而同一种植物在其催芽、育苗和成品种养的阶段都需要不同的光强来配合。以龙舌兰科为例，很多人都认为它们必须强光照才能发育正常，但实践证明它的催芽和育苗都喜欢在50%遮阳的情况下才能生育正常，如在缺乏遮阳条件下会出现发芽率偏低和小苗生长不良，而只是在小苗一般达到30cm高以后才可以接受全日照。
光质是指日光的不同频率波段。一般来说，短波段的紫外光对很多植物的生长有制造短茎和枝叶紧密的效果，而长波段的红外光则会产生徒长效果。懂得利用不同遮光度或反光性的材料可以控制植物的生长速度或造型，也可以间接性的导致防虫目的。很多昆虫的导航系统是依靠紫外光，增强或减弱光线便可令它们盲航。
光照时间会对很多所引品种的花芽制造有决定性的影响。举例说，短日照才开花的圣旦红在长日照的情况下会继续其营养生长，而不会进入生殖生长，从而不会变色开花。相反地雁来红则只会在日照超过10小时的情况下才会制造花芽，不然的话怎么给水催肥打激素都无补于事。
明白了光线对所引品种的影响之后，便可评估自我设施能否配合，然后才决定引进。
(2) 温
每种植物在其催芽、育苗和成品栽培的阶段都有一个特定的适温范围，超出了这个范围会导致各种生理病或死亡。从热带雨林所引种的产品，一般它们的最高至最低的适温范围只有8C，因为这是热带雨林的每日的平均温差。如果把此等品种放在广州地区一个没有加温设备的钢架薄膜大棚里自然越冬，换来的是严重生长不良或死亡。
有些人认为持续高温就必然带来快速生长，其实这是一种错觉，而必须看所引品种来定。举例说，许多商用草花都来自温带地区，它们的开花适温普遍在15C - 25C之间，在华南地区如果生产设施没有控温设备的话，在夏天便完全不能控制开花期，或是花量七零八落，不能达到生产目的。
从催芽角度来看，某些种子或种球是需要一段低温休眠期才会发芽，例如百合和朴树，它们都必须放在5C阴暗的环境里两个月左右才能打破休眠期，否则发芽率很低。如果引种前不先搞清楚这点，千辛万苦才得到的种子，最终也是徒劳无功。
(3) 湿
每种植物都有它本身喜欢生长的湿度范围，如果长时间超越这个范围，它会生长不良或死亡。举例说，叶片宽大而稀薄的阴生植物例如竹芋类就非常害怕低湿度，往往在相对湿度50%左右就会出现叶片卷曲的自我保护情况，如果不即时加湿，到25%相对湿度时，便会出现叶缘枯黄，不到几天它的地上部会慢慢枯萎。当在加湿的时候也要同时小心真菌的发生，否则只会导致顾此失彼。
如果所引种的植物是来自沙漠地区的话，情况就刚好相反。作者的经验是在没有全天控的生产设施里，降低湿度比提高湿度往往是更加困難，而在大田生产的话，只得听天由命。广州地区的春夏交替间，相对湿度可达99.5%，而一个晚上可下900mm的豪雨，相等于美洲沙漠的几年雨量，这就是为何某些仙人掌产品例如金琥在华南地区是引了又引，没有办法生产出来。
(4) 水
这里指的主要是水质和给水量，而水质里面又涉及pH、EC值、含菌量、含矿量和有机物成份。
水质对某些热带雨林品种的生产非常重要，例如洋兰类和凤梨类。这两种产品只能供给象天然雨水般水质的水，才可避免发生种种生理病和菌害。对大部份阴生植物的生产来说，水质要求是pH接近6.5，EC值在0.5以下，含菌量低于1%，含矿量在0.1%以下，有机物含量在1%以下便可算是好水质。如此水质在广州地区的河涌很难找到，一般较为有规模的生产商都会自行挖井抽取地下水，因为地下水的水质较为稳定。作者对自我生产的用水每三个月都会送到检测部门去检查水质，以确保生产用水达标和能够即时作出调整。
给水量对某些草花的生产至为重要，以洋凤仙为例，其植物体内98%左右都是水，如果生产过程中三天缺水，差不多可以肯定会造成大量植株死亡，而这种情况在广州地区会因为仃电或水井缺水而出现。相对来说，如果把多肉植物的成品生产安排在大田里面，例如仙人球类，则一周间的雨水已足够催毁整个生产，导致血本无归。
(5) 肥
适当施肥是保障快速生长和抗病保质的关键所在。在引种以前，引种者必须先弄清楚所引品种的施肥要求。肥料主分有机和无机两大类，而两种都有自身的优点和缺点。一般来说，催芽的阶段应该不施肥，小苗阶段以施无机肥为佳，而成品生产则以施有机肥为好。
无机肥的优点在于肥力猛，使用简便，但缺点在于肥效短，重覆使用会造成地下水源污染。虽然市面上有各种各样的号称缓解肥，又声称肥效在三个月以上，但作者的经验并不苟同，因为施了三个月以后，很多植株根本看不出有明显的生长效益，有可能是实验室的环境跟大田生产是有所不同吧。
有机肥料是近年在欧美地区大力推荐的施肥方法，目前也有袋装的商品肥出售。作者则喜欢利用植物废料和动物粪便自制有机肥，因为可以自我控制品质。一般来说，热带雨林的附生植物和沙漠植物是不喜欢施有机肥，因为有机肥会招致大量的泥土微生物活动。很多棕榈科、苏铁科和绿化工程花木都可以直接施用未经腐熟的新鲜有机肥而不会出现烧根现象，只要在用量上面小心和配合生长季节进行就可以，并不如很多书本所写有机肥非腐熟者不可用那么绝对。
(6) 植料
这里指的是种植栽培用的介质，大概可以分为带土和无土两大类。国际上采用无土栽培的生产商主要是为了通过进口检疫这一关，因为无土栽培的成本效益远远低于带土栽培。无土栽培的另一个缺点在于介质里微生物活动的减少，例如缺乏蚯蚓、线虫和共生菌等微生物去增氧或制造养分，同时又会缺乏微量元素和令到植物根部缺乏物理缎炼，从而在生产上需要采取补救手段。在植物世界里，可能唯一在大自然环境下适应无土栽培的植物是附生性植物，例如空气草类、洋兰类、凤梨类等等，如果引进的品种属于这一类的话，无土栽培是无可避免。
带土栽培是目前华南地区花木生产的主流，许多从国外引种的无土栽培植物在抵步后都会重新被改为带土栽培。目前带土栽培的手法五花八门，有用纯泥土的，有用泥土渗进泥炭土、珍珠岩、蛭石、石棉、沙石、陶粒、木屑、有机肥料等等的，很难说那一个配方是特别好，必须对症下药。
合适的植料对引种生产来说是非常重要的一关，因为植物摄取水份营养都是依靠植料，选用错误的植料配方去进行栽培是注定引种失败的主因之一，然而正确的配方必须依靠经验和不断尝试去找出，别无他法。
(7) 病虫害
如果不能控制所引品种日后所产生的病虫害，则一番辛劳的成果只会白白送给病虫去瓜分。在引种以前，必须先考虑到所引品种在现有生产条件下的抗病抗虫能力，也要考虑到日后如果真的发生病虫害之时，自我条件下有否药物和其他手段去治病治虫。
某些植物在其原生地点可能有很高的抗病抗虫能力，但是引到中国以后，由于气候、泥土、光温湿度的改变，其抗病抗虫能力也可能有所改变，所以必须预先研究调查清楚才可引进。在决定所引品种可能会发生什么类型的病虫害时，必须同时考虑环境因素和水肥问题，必须全盘考虑真菌、细菌、线虫和害虫同时的综合性影响，因为在实际生产过程中，病和虫是经常相互影响，绝少单一行动。此外植株由于缺素症所引起的生理病状，很多时候被错误判断为菌害，以一般生产者都缺乏实验室设备或学术水平去详细分析病源时，只得靠自己的经验或国外文献去尝试找出原因和对付方法。
对于已知的某个品种容易发生的病虫害，例如海枣类的红棕象甲虫，引种者是最好不要引进如此品种，但这个也要考虑栽种地点。红棕象甲虫在粤西和海南岛发展很快，但在广州北部和福建沿海却很少听到，这个有可能与虫体越冬的能力有关，如果虫体不能越冬，那么它的繁殖能力肯定有限，也等如说在粤西和海南就不应引进海枣生产，而在广州北部和福建沿海就可以作出尝试。
(8) 风力
风力对在大田生产的所引品种会有一定的影响力，某些怕风的品种，例如棕榈科里的阴生品种，如果整天放在大田里的阴网下吹风的话，肯定造成叶缘枯黄和长势缓慢，从而丧失商品价值。如果生产基地是在海边的话，海风里面的盐份会对许多植物造成伤害，特别是所引的品种的原产地是热带雨林。
普遍来说，草花、鲜切花、洋兰、阴生植物、仙人掌和多肉植物的生产风力不应超过4级，否则会导致各种弯曲变形、植株矮化的生理变异。与此同时，此等产品又不能在零风力的条件下正常生长，不然会导致病害发生。此等品种的最佳的生产场地是在一个能够控制风力的密封温室里，如果自己没有这种条件就最好考虑避免引进。
广东沿海地区每年夏天都受到台风吹袭，风力可以达到12级，而且夹杂著豪雨，到了冬天又括起东北季候乾冷风，湿度可低至20%。由此可见，引种到广东沿海大田生产的品种必须能够敖过这两个极端，而并不是许多被引品种的原产地是具备象广东沿海这种特殊气候条件的，所以在引种前应该小心考虑。
* * * * * * * *
结论
引种是一种艺术。要成功引种一个品种，引种者需要冷静的科学头脑、耐性、时间和不怕屡次失败的好奇心。目前香港的绿化项目很多都要求采用国外品种，例如迪士尼乐园内外就设计下大量的澳洲和美洲品种，当中有不少从未踏足香港，这可说是引种的另一种表现。
本文希望对有兴趣从事异地引种的人仕有所帮助。
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