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onsdag, januari 26, 2005

Austrocactus

Description of the genus
Austrocactus are smallish barrel cacti which are grossly similar to the North American Sclerocacti, with similar cultural requirements to Sclerocactus.The plants often have hooked spines, but just as often not. This has been the basis for some of the several synonyms in the genus, but is useless as a taxonomic trait, as in almost all populations both types occur (sometimes on different stemsof the same plant).
Austrocactus is also clearly defined. These (in all 5 species) have fruit which dehisce very characteristically and are dry (some species juicy before dehiscing), and the seeds are also very characteristic.
Based upon seed, fruit, flowers, and stem, Austrocactus seems most closely akin to true Pyrrhocactus (i.e. strausianus and closest kin,or those with hard dry dehiscent fruit).

Austrocactus distribution is more or less Patagonica plus mountain areas in east Chile. It also grows into southern Mendoza.

Species
Kiesling in Flora Patagonica V (subtitle Cactus de la Patagonia), recognises 3 species in Argentina, namely
Adriana Hoffmann reports 4 Austrocactus from Chile.

The spiniflorus, philippii, hibernus are endemic to Chile while the last is a typically Argentine species.
The present status of Austrocactus philippii is questionable. Is it rare or extinct as Hoffmann suggests? Or is itthat its actual native habitat remains unknown?

Description of the species


A. bertinii
A large bodied species and similar looking to a Sclerocactus, with stems usually well over 5 cm in diameter and over 10(-30) cm tall when mature. These usually have hooked spines when immature, but commonly the spines become straight in larger plants.
In habitat it can be difficult to distinguish this with Pyrrocactus strausianus, even for a trained eye. Stems are normally single headed or with only a few offsets, but near the coast in Rio Negro (northeast part of it range) there exist populations in which the plants forms large hemispherical clumps of stems.
Flower is yellowish, brownish, orange-brown, or similar hues. The flower looks like flower of Pyrrhocactus strausianus. The fruits dry quickly and split dehiscently.
Distribution; This species ranges from Southern Mendoza to eastern Rio Negro and south to Chubut and into Santa Cruz along the coast, abundanty in scrub desert and grassland.
Habitat: It always seems to grow between the mountains and the coast, but never up into the mountains, A. bertinii doesn't not occur the Andes , with the exeception of the southern Mendoza and Neuquen as it does climb into the foothills.
Accociated plants: Larrea species(Creosote bush), Pterocactus tuberosus , Gymnocalycium and Pyrrhocactus strausianus, Notocactus submammulosus, and Trichocereus candicans in the north and with Maihuenia patagonica and Maihueniopsis darwinii/hickenii and other Pterocactus in southern (and not uncommonly Magellanic Penguins).




A. dusenii
A. dusenii is a small species with stems rarely as thick as 5 cm. It tends to form clusters but rather loose and always creeping or sprawlinig. They will grow rhizomes and send slender shoots between rocks, through cushion plants, or through the soil, sometimes for over a meter, sending up series of stems anywhere one can get through (or out the bottom of a pot).
A. dusenii is a highly variable plant. The plants growing in most areas generally have gray to brown or blackish spines (often quite black when spines are new), but the plants growing in more sheltered canyons in the mountains often have white to yellow spines (particularly in western Chubut). Most of the brown and later grey central spines are hooked.
Flower is large , more often white to pink, somtime yellowish, but variable, and with longer tubes than bertinii and are a bit reminiscent of a Lobivia or Echinopsis flower. The fruit is little juicy before it dries out, but after they do dry, they dehisce in the same manner.

Distribution: A. dusenii favoring higher elevation or more southerly latitudes than A. bertinii. but it exist in Uspallata at 2300 to 2500 m above sea level in the region between the provinces San Juan and Mendoza. It is very common at the sky area Las Lenas in Neuquen, southern Mendoza (in the mountains). It is one of the southernmost occurring of all cacti (but Pterocactus australis seems to hold the record as the most southern).

Habitat: scrubby deserts similair to bertinii , except that it occurs further south in cooler regions and climb into the Andes and maybe cross into Chile.
Associated Plants: Maihueniopsis glomerata, Maihueniopsis russelii, Opuntia ovata, Denmoza and Trichocereus formosa (in northern regions)



A. patagonicus (Weber) Backeberg
Problematic species. Sometimes considered a synynoms of both species mentioned above, sometime by it's own. Most pictures on the web showing this one is really bertinii.
The original description seems to point to the large species which was first named A.bertinii and subsequent authors all seem to agree. The problem it is reported being in Chile. On several places from the states of Mendoza to Santa Cruz (Argentina) the dusenii species crosses the border into Chile, but have never the bertinii come even close, it likes hot desert places (but it could follow a low valley somewhere in northern Patagonia into Chile, but which one?).
Distribution:Argentina. Only known by one population near Chile, Chico southern Chile




A. spiniflorus (Philippi) Ritter
Plants with several stems arising from branching underground stems. Stems are clubshaped, blue-green, to 20 cm long and 4.5 cm in diameter. Ribs are mostlty 6-8, obtuse, shallowly notched. Spines needlelike, straight, brown in colour and with darker bases. Central spines 1-3, 1.5-2.5 cm long. Radial spines 5-8 , spreading less than 1 cm long.
Flowers are born laterally, purplish red, 6-8 cm long. Fruits ellipsoidal to club shaoed, yellowish,spiny when immature. 5 cm long and 2.5-3 cm in diameter.
Distribution: A. spiniflora grows in southeast part of Santiago in the mountains of Mina Las Aranas, Chile

Habitat: Rocky slopes



A. philippii (Regel &Schmidt) Buxbaum & Ritter
Plants often branched, columnar, greenish, slender, creeping or erect, 10-40 cm ling, to 3 cm in diameter. Ribs 7-10 are strongly tuberculate. Central spines 1-5. stout, sharp, straight, yellowish brown, 1-3 cm long.
Flower are yellowish brown, 4-5 cm long. Fruits green and white, mucilaginous
Distribution : Upper part of Cordillera de Maule , Chile.




Synonyms
A. coxii see A. dusenii
A. gracilis see A. bertinii
A. hibernus Ritter see A. philippi.

Taxonomical doubts
Taxinomical doubls has been raised by David Ferguson regarding one to three Pyrrhocactus species.
Here is a experpt from his arguments:
Maybe should Austrocactus also include some of the Pyrrhocactus (i.e. strausianus and kin ) = those with rough seeds and dry dehiscent fruits).
Some say the flowers of Austrocactus and Pyrrhocactus are different, those of Austrocactus being larger with a longer hypanthium. However, A. bertinii and P.strausianus have flowers which are very similar. The rest of Pyrrhocactus (in all one or two species) is well defined as well, but needs a new name if considered as a full genus (and not to Eriosyce), since the type species of Pyrrhocactus is strausianus! These other, the remaining "Pyrrhocactus" species have short vase-shaped flowers, fleshy but hollow fruits which are non-dehiscent, and shiny seeds very like miniature Copiapoa seeds (not so flattened).
The length of the flower tube, and the difference in length between the inner and outer groups of stamens is cited as not allowing this relationship, but species of Austrocactus vary on these points as well, and these traits vary widely within several other genera of Cereoids. There are no significant structural distinctions, this is just citing measurements again.
Also the overall morphology of these two species is very similar. The two sometimes grow together as well , which added to the initial confusion.
The seeds of Pyrrhocactus and Austrocactus to be very similar. In fact it is difficult to impossible to separate the seeds of certain species if they become mixed. The seeds vary some from species to species, but show a nearly discoid shape with a sublateral hilum, micropyle distinctly outside of the hilum (unusual in Cereoid cacti), and rough, often ridged (for lack of a better term) epidermal surface. They tend to look brownish gray, but this seems to be at least in part do to the surface texturing, with the actual underlying color being near black. The seeds of some species are less ridged than others. Seed size varies from species to species, but in all are rather large as compared to those of most species of the related Neoporteria/ Neochilenea/Islaya alliance. The seeds of Eriocyse [sensu strictu] are quite similar to those of Pyrrhocactus and Austrocactus.
The fruits of Pyrrhocactus [minus umadeave and bulbocalyx] and Austrocactus bertinii are the same as those of Pyrrhocactus in basic structure, in drying rigid when mature, and in mode of dehiscence, and these are very different fruits from the rest of Pyrrocactus.
Fred Katterman disagree with Dave Ferguson regarding the close relationship to Pyrrhocactus. According to F. Katterman there are distinct differences. In the flowers the anthers are in two series, one hugging the style and the other group hugging the tube. In Eriosyce section Pyrrhocactus no such division exists. F. Katterman says that seeds are also very different, but then he refer to Eriocyce not true Pyrrhocactus [sensu stricta, incl. strausianus and kin ].

Cultivation
All species are very cold tolerant, and they can survive to at least -20 C maybe lower temperatures.
A. spiniflora is covered by snow in 3-4 months during winter time.
A. bertinii likes hotter climate than the rest.
Everybody should also keep in mind that second after Austrocactus, which as a very similar geographic range, Maihuenia patagonica is one of the three species of Cactaceae with the southernmost overall distribution. Only one species each of Austrocactus (A. patagonicus) and Pterocactus (P. australis) extend farther to the south according to Kiesling (1982, 1988, 1990).
They appear to have a short growing period from in Sweden late April to end of June, although giving water through the summer months but sparingly is a good idea. During the summer months they should put outside. Well drained compost is beneficial.

Seeds seem hard to germinate and probably need cold stratification and they die more easily than other seedlings from other species. Once they have been established it grows rather quickly first year.

It has been reported that people have tried pre-frozen (much as people would treat Sclerocactus and Pediocactus seed), regular preparation, sowed on gravel, or sand, under the surface, on the surface, in high warmth, low temperature like 17C and yet very low germination rate. Maybe they are like Tephrocactus, there appears to be a high degree of sterility in the seed.


For an article on this plant see:
Stephenson, R. (1992) EXTREMELY SOUTHERN
CACTI. British Cact. & Succ. Journ. 10 (3): 57-58, 2 figs.






mats rolfson, 23:36

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