A word of caution before we get carried away criticising Roy.
I am a repeat customer of Imen's and out of a sense of loyalty / familiarity felt instant indignation when reading Roy's reply but, firstly Imen started the 'attack' and Roy may have felt angry also.
Something stirring at the back of my mind clicked with the single trunk idea, and an image in my mind of the trees in Fenghuang as opposed to the bushes of Min Bei and Min Nan. When trying (and failing) to discover the origin of Shui Xian I came across the notion several times.
Mary and Robert Heiss subscribe to the Single Trunk explanation/translation for Dan Cong. Pages 155 and 156
http://books.google.co.uk/books?id=3NBt ... sh&f=false
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Perhaps in the heat of the moment, our 2 friends are talking from different heated standpoints.
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Latin, Ancient Greek and many other dead languages are fixed, but living languages evolve and change, and words take on new meanings ( I still don't appreciate when you youngsters describe something as 'sick' - if you mean good or bad

)
It is possible - realms of unsteady hypothesis here

- that originally Dan Cong meant Single Trunk 'and still should'
BUT
that because each tree until cloning started (which was fairly recently) was unique, with different flavour profiles, that encouraged where viable the processing of each tree seperately. This essential step in discretely analysing and appreciating the lone tea tree/bush for it's own merits has a great appeal to the serious Dan Cong student and can seem an easy way in how the term would evolve a different meaning, which is now an acceptable usage because we are talking about and in a living language.
since cloning and the needs of commercial enterprises we can see how Single Grove can come to be an acceptable usage of the term Dan Cong.
So How
- Perhaps Dan Cong - tea - is really - only a class of tea made from true descendants of the original 'Shui Xian' trees, that has been made in the Dan Cong fashion. The Anxi Tie Guan Yin process has a different number of processing steps to the Yan Cha process, maybe the Dan Cong process has a recognised production pattern which helps to make it a Dan Cong?
It could then be all of the above, Single Trunk, Single Grove and Single Tree/Bush - with Single Tree usually at the Apogee of the Class.
The translation then relies on the facts of the particular instance?
There have been occasions when trees have been neglected, and then brought back into use after many decades of non use. This could account for very old trees which do not have the single trunk.
More pertinent would be when new 'groves' have been planted in the last 4 decades what form of arboriculture is being practised, do any photos of new trees show the single trunk being maintained?
It would be nice to get Roy and Imen working together collaboratively - each with an Olive Branch in hand - to truly inform their tea drinking friends with a common understanding.