Sadly this landscaped garden no longer exists as shown
 
Ag. americana v. variegata ( marginata ) Ag. applanata Ag. arizonica Ag. boldinghiana Ag. leopoldii ( = filifera X schidigera ) Ag.macroacantha Ag. mapisaga Ag. marmorata Ag. mitis v.albidior Ag. parryi Ag. parrasana Ag. polianthiflora Ag. potatorum Ag. pumila ( adult form ) Ag. toumeyana v. bella Ag. toumeyana ssp. toumeyana Ag. sp. Ag. utahensis ssp. kaibabensis Ag.utahensis v. nevadensis Ag. utahensis Ag. victoriae reginae Ag. victoriae reginae f. fernandi regis Ag. victoriae reginae variegata (since 2011 renamed as Ag. nickelsiae ) Ag. victoriae reginae f. viridis ( = Ag. victoriae-reginae f. fernandi regis x lechuguilla )
 
This plant has been at Hollygate for many years now and arrived labelled as agave nigra. This term is generally accepted nowadays as referring to hybrids between agave victoriae-reginae and agave asperrima. In April 2007 in Succulenta, the magazine of the Belgian and Dutch Succulent Society, there appeared an article by Alsemgeest,van Roosbroeck and Walderveen describing the four major forms of agave victoriae-reginae, based on studies of these plants whilst travelling through their natural habitat. The form 'viridis', first described by Breitung in 1968, is found in the Saltillo area and considered to be a hybrid between the fernandi-regis form of agave victoriae-reginae and agave lechuguilla. These plants lack the characteristic markings of other forms of victoriae-reginae. The Hollygate plant appears to be this form.
The full article, translated into English, is to be found here : http://www.agaves.nl/Articles/E_victoriae%20reginae.htm
 
Gallery 1 Mixed agave photos plus photos from Ernst Woelfing
Gallery 2 Mixed agave photos
Gallery 3 and Gallery 4 .Photos from Julia Etter and Martin Kristen
Gallery 5 Photos from Gerhard Koehres
Gallery 6 Photos from Mountain States Nursery
Gallery 7 Photos from Liguria and Cote d'Azur from Dr. Thomas Heller
Gallery 8 Habitat photos from Mexico from Nick Macer plus Alexander Heim's garden near Athens
Gallery 9 Photos from the Hollygate Cactus Garden/Nursery, UK
Gallery 10 Photos from his exotic garden plus Mexican habitat photos from Paul Spracklin
Gallery 11 Habitat photos from Mexico & USA from Wim Alsemgeest
Gallery 12 Photos from Cactus Oasis, a succulent paradise in eastern Holland
Gallery 13 Photos from Kew Gardens, London
Gallery 14 Photos from Phillipe Faucon
Gallery 15 Habitat photos from Greg Starr
Gallery 16 Photos from the private collection of Ron Parker, Fountain Hills, AZ
Gallery 17 Mexican & USA habitat photos from Bertus Spee
Gallery 18 Photos from Michael Greulich.
Gallery19 under construction
Gallery 20 UK National Agave Collection