U vindt dit artikel in de Nederlandse taal in Succulenta No.5 van oktober 2007

Agave xylonacantha Salm Dyck and heteracantha Berger

This article is a copy of an original article in the Dutch journal of the Dutch Cactus and Succulent Society 'Succulenta'' (oktober 2007) and has been translated into English by Jan Kolendo England.

Wim Alsemgeest  Jos van Roosbroeck and Theo van ‘t Walderveen

Scan from Agave xylonacantha out of Curt.Bot.Mag. (Collection Roy Mottram England))

History.
Agave xylonacantha,like so many other  agaves in the 19 century, was initially discribed by the well known Count Joseph-Maria von Salm-Dyck in 1853 who had an extensive collection of succulents in his castle in Düsseldorf, Germany. At that time every plant coming from a far away exotic country  was considered a treasure. Many plants, as we now know, were taken from habitat and found their way not only to varioust botanical gardens but also to the collections of the rich and famous. These people ware so proud and delighted with their plants that they tried to give each individual acquisition an individual botanical status.
So for example, Pampanini, Jacobi, Regel and Berger described numerous plants that we no know to be variations of one and the same plant. Communication at that time were not as rapid as they are now with eg.internet systems and sharing of information was not as speedy as can be achieved in today's times.The consensus currently is that,as far as nomenclature is concerned, the oldest names and descriptions have priority and all newer versions are consigned to history.At present not only many botanists but also many amateurs enthusiasts are busy trying to work out what was done in the past and trying to make some orderout of that chaos. Currently there are some 20 synonyms for Agave xylonacantha and that in itself says a lot.

The older names can still be found in many books and journal articles. Sometimes having an older name is quite useful because it may help in tracing the history of a plant back to an orginal source. In many old botanical gardens one can find plants with their old orginal names and this is more common than in private collections.

Our Plant

Why we refer to Agave xylonacantha in this article as “our plant “ ??

Our plant, not Agave xylonacantha but agave heteracantha

Plants in collections under the name of A. xylonacantha tend to be grey/green in colour, with an light green middle stripe on the leaves. On the underside of the leaves one can see  many small stripes and the surfase is often quite rough.Apart from the end spike one can see on of the side of the leaves many variable teeth on broad bases; some are double and some variously flexed and hooked.Apart from the end spine one can see on the side of the leaves many variable teeth on broad bases; some are double and some variously flexed and hooked. The margins of the leaves are initialy brown and later grey and together with the changing of colour of the leaves this makes for a beautiful plant, especially specimens with numerous leaves.
The flower spike is a spicate form, a small column of flowers, and this places the plant in the Littaea  group. Theses are the most typical  characteristics of the plant.

Our plant grows with an asymmetrical rosette  so it is immediately recognisable. We talking here about  a specific form , because we are coming to the conclusion that  our A. xylonacantha, is the plant we have in our collections not the typical A. xylonacantha but more about this name later. From now  we' call our “A. xylonacantha”  Our plant!

Two young plants, left the green A.heteracantha and richt the an gry/green seedling of A. xylonacantha

The Asymmetric rosette of “our plant “

There are also   small forms of “our plant in the collections, with different names such as  A. xylonacantha var. minor,  A. univittata and  A. univittata var. minor.
You can find a good picture in the first edition of Dr. Thomas Heller’s book “Agaven” on page 128.
Another characteristic growth feature  of “our plant” is  that the new central leaves of the plant do no grow straight upwards but appear horizontally.  We think that the reason is that the plant does not have a  typical symmetrical central axis.
This typical growth system you can also find in the plants under the name of   A. xylonacantha ,,minor”, A. univittata and A. univittata var. minor.

The "real" agave xylonacantha in cultur collection Jos van Roosbroeck Belgium

Is “our plant” now A. xylonacantha or A. lophantha ?

Our plant look's very much on A. lophantha sometimes also to be found under the name of  A. univittata but this latter name is now no longer used under the rules of botanical nomenclature .
Many times you may see “our plant” under the name of A. lophantha but also you can also find hybrids  of A. xylonacantha with  A. lechuguilla, A. ghiesbreghtii, A. filifera  and A. attenuata .
Naturally it is not easy to find out what the correct name of “our plant’ is, as it  is a long time ago that these plant were brought from their natural home to Europe and described.
There is an interesting story to be found  in Berger's book from 1915 “Die Agaven”. Lt.Gen. G. von Jacobi saw in Count Oswald de  Kerchove de Denterghem’s collection plants of A. univittata (now A. lophantha) and A. xylonacantha together in flower . Many seeds were collected later from these plants and so many young plants arose from these two different specimens. Maybe these are the ancestors of “ our plant ”
Agave lophantha is different from  A. xylonacantha because of the many smaller teeth but just like A. xylonacantha they also have double teeth.  The teeth of “our plant” are much bigger than average   and their colours vary  from yellow to grey. They are often described as  “wooden teeth”.  Another important  characteristic of A. lophantha is the flat leaves, whereas most of the other agaves, including “our  plant ”, have leaves which are concave .

An green and an grey/green form of Agave xylonacantha between Zimapan and Rio Moctezuma

In the natural Habitat

We continue to have  doubts that   “our plant” is correctly named as A. xylonacantha.
We are now living  in such times  that many amateurs like us  have the possibility to go and look for the  the plants in habitat.   So we hope that we can solve the mystery of these names and have a lot of fun and pleasure in doing so.

Agave xylonacantha with an broken flowerstalk on the same site

Two years later we were again in the same area and we again found on our route an A. xylonacantha with  an short flower stalk. At first we thought  we had found an unusual  A. xylonacantha form with a short flower stalk, but the final conclusion was that the flower stalk was simply  broken. So you can see how easily confusion can occur.

We have also visited the site of A. xylonacantha. near San Luis Potosi, in the neighbourhood  of the well know site described by the  “Globe Trotters”. The plants growing there are much bigger with more green-yellow colouring of the leaves but they also have the double teeth  and the rough underside of the leaves as in the picture.
The third site of  A. xylonacantha we visid is in the fames  Baranca de Los Venados near Meztitlan, there were we the well known ' Old Man Cactus' the Cephalocactus senilis also grows.
Here one can see many A. xylonacantha hanging on cliff walls. The plants here are only the grey- green variety, without any yellowish/green forms. There are true  wall growers on vertical cliffs en that is the reason the leaves have a different form and are also far fewer in number. The leave are long and the plant are not very attractive and generally not recommended for a window display.
The plant you can find down flat onder flatter ground, have more or less the spiral growing system but also in culture you can see that same spiral growing method. These are very ugly plants. Later we find also on vertical cliffs near  Bella Vista Del Rio more A. xylonacantha and again the plants there demonstrated spiral growthing with the asymetrical growing as found in "our plant".

If you look at the very old descriptions you find out that the A. xylonacantha plants growing on vertical cliffs adhere to the growth deevelopment described there..

Separate you find in this context the old descriptions.Click here.

In our opinion, the true form of  A. xylonacantha is the  the ‘ugly’ form growing on the vertical cliffs  in the Baranca  Meztitlan and also near Bella Vista Del Rio. In the  agave bible, the famous book of Howard S. Gentry ‘The Agaves of Continental North America,  the author states ‘ the species is abundant on the limestone slopes in the Barranca de Meztitlan, not far from the great mines of Real del Monte’.
Real del Monte is the city not far from the city of  Pachuca, in the state  of Hidalgo.We now have young plants grown from seed coming from the original site and we discover that these young plant are much greyer in colour than  the young  offsets  from  “our plant “, which appear to be much greener. So therefore what is the agave present for an long time in our collection with the name A. xylonacantha and now known only as “our plant” ? Is “our plant” perhaps A. heteracantha?

Alwin Berger
Berger described almost all of his agaves from plants growing in The  Hanbury Gardens in  La Mortola on the Italian  Riviera.

, but that is an error and should refer to page 593.  This picture and the description brings us to  “our plant”.

Berger tried to obtain the paper with the description of  A.heteracantha by Zuccarini from 1883 but was not successful.

A. heteracantha appeared in the collection of  Jacobi and Salm-Dyck and  Salm-Dyck described the stripes on the leaves; Berger concluded that this was the right plant and described it as  A. heteracantha  A. Berger.

The confusion is complete with the knowledge that there are three different descriptions  of A. heteracantha, all taken from different plants.

1. A. heteracantha Baker, Gardeners'Chronicle, 1877: 369, fig. 59.
    This name is  a synonym of  A. ensifera (Gentry, 1982).

2. A. heteracantha  Hort. This name is a synonym of A. lechuguilla  (Gentry,1982).

3. A. heteracantha Zucc., Acad. Caes. Leop. Carol. 1833 (?), 16(2):675.
    This name is a synonym A. lophantha (Gentry,1982).

There is no explanation of any reason why this is so and it has to be pointed out that the first two allocations of A. heteracantha are not based on a  study of the literature.

Because the picture of Alwin Berger's A. heteracantha,  taken  in La Mortola and published  in   “Die Gartenwelt” from 1898,  looks identical to ‘ our plant “ and the description also fits precisely , have we have concluded that   “our plant” is the real  Agave heteracantha A. Berger.

August J. J. Breitung
In his publication ‘The Agaves’ (1968)  Breitung shows a picture of A. univittata  var. carchariodonta ( picture 22, page 11).
This plant appears identical to the A. xylonacantha one can find growing near San Luis Potosi. In his book Gentry describes this plant as a  synonym of A. xylonacantha. 

Curtis’s Botanical Magazine
The beautiful painting in colour in the famous  Curtis’s Botanical Magazine from 1876 (see the copy in this article with thanks to Roy Mottram), is the  type plant of A. xylonacantha.
This painting is of a plant coming originally from   Real del Monte, north of Pachuca, Hidalgo, Mex., not far from the Barranca de Meztitlan. The plant in the painting flowered in Kew Gardens,London in 1876.
You can see the flower-stalk in the painting. If you look at the centre of the plant you can certainly see the similarities to “our plant”.
But one must also realise that if an  agave starts to  flower then there is also a change in the appearance of the leaves,which become smaller and thinner.
.
If one looks closely at  the underside of the leaves of the plant on the painting one can see the typical striped leaves of A. xylonacantha. Also the pattern of leaf growth suggests  that the plants are coming from a rock wall originally and so this painting makes  a very good lectotype for  A. xylonacantha.

The plants growing near San Luis  Potosi are different in form. These plant are much bigger and more yellowish-green in the colour of the leaves and also have the typical double  teeth , so that these plants also belongs as A. xylonacantha forms, but not to the type of A. xylonacantha growing in the  Barranca de Meztitlan.

John G. Baker
Finally, we can  also find A. xylonacantha in the book written by Baker in 1888.
Baker was working in the  Kew Gardens and had written  another book in 1879,  that means nine  years earlier. This work was translated from the  English into  Italian by V. Ricasoli.In this book you can find different paintings , also one of Ä.xilinacantha,”, This name is missing one “ o “ and one “ n “. This name is synonymous  with  A. xylonacantha. One can also find the name “A.xilacantha” in : “Salm-Dyck - Bot. Mag. t. 5660 - Gard. Chron. fig. 81, vol. VII, p. 527“, also representing   A. xylonacantha.
The painting  of A. xilacantha is a copy from the Gardeners’ Chronicle; it shows the typical cliff-grower plant. However  this typical plant has very small leaves, or perhaps this painter has made them smaller. By looking closely at the painting, one can also find the double teeth.

Conclusion

A. xylonacantha is a very  variable plant, so it is not surprising that we have for a long time not realised that  ” our plant “ does not belong to the true A.xylonacantha.
Now that we have  young seedlings available in cultivation with  precisely known origins, we can see  that  these seedlings have the  green-grey colour of the leaves typical for the  “real ” A. xylonacantha.
The most typical  A. xylonacantha grows in the  Barraca De Meztitlan as a cliff dweller, with a curved rosette and few  leaves. The growth pattern is quite different to the asymmetrical growth of  A. heteracantha.
On flat terrain the plants grow with normal shaped rosettes and more numerous leaves. These plants are typically grey-green in colour.

In Alwin Berger’s  book on page 114, it is mentioned that  C. A. Purpus has collected plants under the name of A.xylonacantha in San Luis Potosi.

Because  “our plant” is so much different to the real “A. xylonacantha” our  conclusion is that  “our plant”  belongs to a different  taxon, this being  the original A. heteracantha  Zucc.   “Our plant” ,now named as  A. heteracantha is a beautiful plant.
There are also smaller forms of  this A. heteracantha, we suggest naming these smaller forms A. heteracantha “minor”

The Cultivation  of A. heteracantha.
.
The forms of A. heteracantha are very strong and winter hardy. We know the story of a plant in Holland completely forgotten about in winter because it was on the roof of a house. When this plant was discovered by it’s owner it was   completely frosted up in the pot, but it appeared to be none the worse from this experience.
We suspect that because this plant is reasonably winter hardy in Europe it can be found in many collections growing without any problems.

Synonyms  from A. xylonacantha:

Agave amurensis  Jacobi  (small form)
Agave carchariodonta  Pampanini (1907)
Agave cornuta  Hort. Belg. ex Besaucele
Agave heteracantha var. splendens  (Jacobi) Terracciano
Agave kochii  Jacobi (1866)
Agave hybrida  Hort. ex Baker  (an hybrid)
Agave maximilliana  Hort. ex Besaucele ( small form)
Agave noli-tangere  A. Berger (1915)
Agave perbella  Hort ex Baker
Agave splendens Jacobi (1870)
Agave univittata var. carchariodonta  (Pampanini) Breitung
Agave vanderdonckii  Hort. ex Baker
Agave vittata  Regel (1858)
Agave xylacantha Hort
Agave xylonacantha var. horizontalis Hort. ex Berger
Agave xylonacantha var. latifolia  Jacobi
Agave xylonacantha var. macracantha Jacobi
Agave xylonacantha var. mediopicta Trelease
Agave xlyonacantha var. torta Jacobi
Agave xylonacantha var. vittata Jacobi

Literatuur:
Alsemgeest, W. (2002) : Ervaringen met agaven in cultuur(2). Succulenta, 81 (3): 106.
Baker, Dottore J. G. (1879). Succinto della Monografia delle Agave (vertaald uit het Engels door V. Ricasoli). Bull. Soc. Toscana Orticultura, IV, Firenze.
Baker, J. G. (1877). The Genus Agave. The Gardeners’ Chronicle, N.S. 2, vol. ......., p. 527, fig.81.
Baker, J. G. (1888). Handbook of the Amaryllideae: including the Alstroemerieae and Agaveae, p.168. Bell, London.
Berger, A. (1915) : Die Agaven – Beiträge zu einer Monographie.  Fischer, Jena   (Idem, ergänzter Nachdruck der 1. Auflage, 1988, Gustav Fischer Verlag, Stuttgart, New York).
Berger, A. (1898) : Agaven - von Alwin Berger Kurator des Akklimatisationsgartens zu La Mortola. Die Gartenwelt, Jg. 2,  September 1898,  no.49 und 51.
Breitung, A. J. J. (1968) . The Agaves. The Cactus  and Succulent  Journal Yearbook. Abbey Garden Press.
Curtis’s Botanical Magazin, 18 ........, vol. ........., t. ......(with text): Agave xylonacantha.
Etter, J. &  Kristen, M. (2004): A Roundtrip Through  San Luis Potosi. Cactus&Co, 8 (2): 69-86.
Garcia-Mendoza, A. (2002). Distribution of Agave (Agavaceae) in Mexico. C.&S.J.(US), 74 (4): 178.
Gentry, H. S. (1982). Agaves of the continental North America. The University of Arizona Press, Tucson.
Hamburger Garten- und Blumenzeitung (Verlag Robert Kittler, Hamburg), 1864, Jg. 20, S. 550-551.
Heller, Th. (2003). Agaven. Natur und Tier Verlag GmbH,  Münster
Irish, M. & G. Irish (2000).  Agaves and related Plants – A Gardeners' Guide. Timber Press, Portland Oregon.
Jacobi, Generalleutnant G. A. von (1864). Versuch zu einer systematischen Ordnung der Agaven. Hamburger Garten- und Blumenzeitung (Verlag Robert Kittler, Hamburg), S. 455-466, 498-515, 539-562.
Jacobi, Generalleutnant G. A. von (1866).  Herzug zu einer systematisichen Ordnung der Agaven. Hamburger Garten- und Blumenzeitung (Verlag Robert Kittler, Hamburg), S. 114-123, 167-178, 209-222, 261-273, 320-331, 353-361, 404-413.
Jacobi, G.A. von (1867). Agave xylonacantha. Hamburger Garten- und Blumenzeitung (Verlag Robert Kittler, Hamburg), S. 555-556.
Jacobi, G. A. von (1869). Nachtrag zu dem Versuch einer systematischen Ordnung der Agaven. Abhandlungen der Schlesischen Gesellschaft fur vaterländische Cultur. Abtheilung fur Naturwissenschaften und Medicin (Breslau), S. 138-176.
Jacobi, G. A. von (1872). Zweiter Nachtrag zu dem Versuch einer systematischen Ordnung der Agaven. Abhandlungen der Schlesischen Gesellschaft fur vaterländische Cultur. Abtheilung fur Naturwissenschaften und Medicin, Breslau, S. 147-175.
Jacobsen, H. (1955) : Handbuch der sukkulenten Pflanzen.  Fischer, Jena.
Korevaar, L.C. et al. (1983) Wat betekent die naam. Botanisch Latijn toegankelijk gemaakt.Kon.Van Poll, Roosendaal.
Thiede, J. (2001). Agavaceae. In Eggli, U. (Hrsg.), Sukkulenten-Lexikon, Bd. 1, Einkeimblättrige Pflanzen (Monocotyledonen). Ulmer, Stuttgart.
Ullrich, B. (1991).  Agavensystematik für das I.O.S.- Lexicon (1. Vorschlag) 3/1991.

Websites:
www.agaves.nl
www.agavacea.com
The International Plant Names Index (IPNI): http://www.ipni.org

Thanks to  Sjef Theunissen the help us with the translation from the original describing from Latin in to Dutch.
An thanks also to Jan Kolendo for the help from the translation from the hole article from Dutch to Englisch.

Many thanks for the help by the translation from Dutch to the Englisch language from Jan Kolendo

Literature:

Breitung, A.J. J. (1968). The Agaves. The Cactus  and Succulent Journal Yearbook. Abbey Garden Press, .............
Heller, Th. (2003). Agaven. Natur und Tier Verlag GmbH, Münster.
Irish, M. & Irish, G. (2000). Agaves and related Plants - A Gardeners' Guide. Timber Press, Portland Oregon.
Janse, J. A. (1942). Agaven. Cactussen en Vetplanten, 8: 51-56.
Thiede, J. (2001). Agavaceae.  In Eggli, U. (Hrsg.), Sukkulenten-Lexicon, Bd 1, Einkeimblättrige Pflanzen (Monocotyledonen). Ulmer, Stuttgart.
Ullrich.B.Zum Verbreitungsgebiet von Agave victoriae-reginae T.Moore. K.u.a.s. 42(11) 1991 pag.262-263
Ullrich.B. Agave victoriae-reginae T. Moore K.u.a.s kartei heft 7/1991.

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