Alcantarea imperialis
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Alcantarea imperialis
Jan Townsend, Green form.
Jan Townsend, Red form, Leme Black .
Photo by Ken Woods, 10/05 Mike Symmons garden.

Peter Franklin, PAF745, Raymond Terrace NSW.

‘Rubra’ is it Valid or NOT ? compiled by Ross Little 2017
In our FNCBS September Newsletter we used the term ‘rubra’ which drew the following response from Derek Butcher.

Let us get rid of the term 'rubra' used with Alcantarea imperialis or at least try. Nobody has defined this quasi-botanical term by writing a description under the ICN rules as a botanist would do. It is not acceptable under the ICNCP rules for a cultivar either.
The following is what Versieux and Wanderley published in ‘Bromelias Gigantes do Brasil’, 2015, which is a very definitive book on the genus Alcantarea: “There is considerable morphological intraspecific variation in the different popu-lations studied, particularly with regard to the colour of the central rosette leaves and peduncle bracts. In the populations of Macae de Cima, in Nova Friburgo, Rio de Janeiro, Brazil, it is possible to observe individuals totally green growing alongside those totally vinous (Barbara et al. 2007). For gardeners, such varia-tions constitutes important sources of selection of cultivars, which can be totally green plants, completely red-vinous with variations between the lighter shades or dark, or plants with leaves almost completely green, only with the tips vinous and peduncle bracts vinous at the base, passing to green concolor”.
Nobody has defined what 'rubra' refers to: Is it the red leaves or red peduncle/primary bracts or must it have both ? Does a tinge of red in the leaves qualify ? The use of the word 'rubra' in this context should be banned from Bromeliad Newsletters. Regrettably some growers will always use the word on their labels even though it has no botanical validity in conjunction with the botanically described, Latinised words Alcantarea imperialis.

After some discussion it has been agreed that there is no way a single cultivar name could be used for this ill-defined red form of Alc. imperialis.
The redness is quite normal however variable the plants may be. Remember the term ’rubra’ is only a descriptive trade or nursery name. The use of such terms should be banned. If you must use a descriptor use “red form”.
If sellers are serious about their use of the name ‘Rubra’ they should select their distinctive forms and think of alternative names and register them as Cultivars.
For similar reasons “Purpurea” should be banned too.
Acknowledgements: Peter Franklin, Geoff Lawn and Derek Butcher.

Updated 29/11/17