The different aspects of the genus Astrophytum Lem. within the cacti family are still poor researched. There exists only one attempt by MEGATA, M. to collect the knowledge in 1944 from a scientific point of view. This site includes to his position new facts and documents from the since past six decades. Despite the considerable extent of the data and number of pictures these collections also remain to speak with the words of MEGATA:
A preciousness from the New World:
Let me introduce the genus Astrophytum (star plants), which contains the high developed stem succulents of Mexico. Their common English name "bishop's cap" is aptly derived from the five ribed shape. The Mexicans also describe the Astrophytum myriostigma as "mitra" (bishop's cap). The genus contains five species and a subgenus Stigmatodactylus, which live in separated areas (Outline).
Astrophytum ornatum (DC.) F.A.C. Web. ex B&R
The evolutional oldest and most southern species is Astrophytum ornatum (ornatum = adorned) from the Mexican federal states Hidalgo, Queretaro, Guanajuato and the south of San Luis Potosi. It was the first bishop's cap that came to Europe in the year 1828. When the botanist De Candolle unpacked the plant from the overseas box he thought, the new and unknown cactus was affected by fungus after the ship journey of some months. But to his astonishment he proved, that the complete body was strewed with white spots of tuft hair. One knows today that these spots represent a characteristic of Astrophytum which only they have. The wool flakes serve perhaps(!) for water collection and also perhaps as protection against the sun. Primarily they have an important function for the mimicry. One understands the visual adaptation to the surroundings by it. It gives the plants a great chance to survive because it offers protection against animal muck and sometimes also against the human collector activity!
Astrophytum myriostigma Lemaire
A very perfect disguise is found at Astrophytum myriostigma (myriostigma = thousand dotted) which the Frenchman Lemaire described eleven years later in 1839. With its five-ribbed thick body, covered with white wool spots and without spines you can find it hardly at its locations between the lime rocks of San Luis Potosi and Tamaulipas. Many cactus collectors discovered and described later varieties in the second half of the 19'th century. One knows even plants without wooly dots (nudes), plants with only four ribs and old Myriostigmas with seven, eight ore more. However, everyone has pure yellow flowers like Ornatum.
Astrophytum asterias (Zuccarini) Lemaire
If an anectode is true, we owe the discovery of the also spineless Astrophytum asterias (asterias = sea urchin) to the desert wind! The German royal Karwinsky had to run after his rolling hat on a journey in Tamaulipas. His sombrero just found cought in the skinny brushwood where just the most beautiful species of the genus grew. The few specimen which reached Europe in 1843 soon disappeared because the culture of the plant isn't simple. The Asterias has been found again by Mr. Fric at the properties of the Mexican landowner Gonzalez 51 years later. The plant is still a rarity today in cultivation. And in its native country it is nearly extincted. One has established another occurrences at the Rio Grande near the Mexican / Texas border at the beginning of the 20th century. However the also very rare Texan Asterias was nearly wiped out soon by unprincipled dealers.
Astrophytum capricorne (Dietrich) Britton et Rose
Astrophytum capricorne (capricorne = goat horn formed spines) was found in 1850 by Poselger and described by Dietrich in 1851. These are the most northern bishop's caps in the states Coahuila and Nuevo Leon. They have thick, long spines and splendid yellow flowers with a deep red throat. Their locations in the deserts of the Sierra de Paila are one of the driest habitats of all Astrophytums. Their spines play an important role in mimicry. In the brushwood they disguise the plants excellently. Some plants look more like an arid tuft of grass than a cactus. There are known the varieties Astrophytum capricorne niveum = (snowily, snow-whitely), senile (senile = old), aureum (aureus=golden), minus (minus=little) and crassispinum (crassispinus = strong spines) .
Astrophytum coahuilense (H. Möller) Kayser
The fifth species of the genus, the Astrophytum coahuilense, also grows in the native country of the Astrophytum capricorne. It got its name of his first found location in the state of Coahuila. It also lives at the border of the adjacent Mexican federal states Zacatecas as well as Durango: so seen the name "coahuilense" isn't very exact. A layman can hardly distinguish the Coahuilense of the "normal" bishop's cap, the Astrophytum myriostigma. The flower shows the difference. While the Myriostigmas have pure yellow flowers as mentioned, the Coahuilense shows a red orange colored center. A closer relationship with the Capricorne is obvious. The scientific systematics has mistakenly nevertheless led these plants as a variety of Myriostigma until the year 1939.
Stigmatodactylus: Astrophytum caput-medusae D. Hunt
The plants were discovered in 2001 at Nuevo Leon and first described as Digitostigma. The recombination to Astrophytum by David Hunt were made because the plants own the characteristic tufts of wool from this genus, have very similar flowers and the same hat-formed seed. They own very long wards with an divided areole. The body above the earth is short but Stigmatodactylus has a mighty, fleshy central-root which can store water over a long time. The only one species is Astrophytum caput-medusae.
Culture and propagation
The cultivation of the Myriostigma and Ornatum might not represent any problem for the dedicated plant friend. They like a sand, loam mineral substratum. A reaction by pH 7 absolutely meets their approval: they settle areas with limestone formations in her native country like our Jura Mountains in Germany. April till September is their vegetation time in our European climate. The bishop's caps spend the rest of the year completely dry at temperatures around 10 degrees centigrade. The most frequent care fault consists that this rest period isn't taken into account.
All other Astrophytums have to be treated similarly. But caution: they don't tolerate a divergent treatment regarding watering and rest period far less. It is worth to take care about these preciousnesses in the plant kingdom, and there is hardly too much light and too little water for them. Darkness, cold and jam wetness take them to danger!
If you buy bunged Astrophytums in a supermarket, then cut the cactuses off to reroot them. (Outline). Let dry the plant at a shady but warm place some weeks and soon new roots are growing. Then put your Astrophytum into the substratum and give careful little water now. Bunged Astrophyten don't look very beautiful. Beside they don't get old on the customary pad because this usually dies soon.
If you want to propagate your bishop's caps by seed, there are more possibilities. Either you cross two simultaneous flowering individuals and reap the seed. Ore still more simply buy seed. Or you cut your bishop's cap in two. (Outline). Let the top dry several weeks until roots appear again as mentioned already. From the remained stump after some time new Astrophytums will shoot .
To raise plants from the cap-formed, 2-3 mm tall deep brown seeds is rather simple. The seeds are scattered only loosely on mineral substratum. One irrigates the planting vessels best by putting water from below. So seed do not swim around in the pots and the required mild humidity settle himself. The first seeds germinate already after a few days at high atmospheric humidity's and temperatures' around 25-28 degree centigrade. Take care that the young seedlings get fresh air. Against fungus attack one can use the easily available Chinosol with good success.
Let your young bishop's caps not quite dry up in the first winter and give them if possible a bright place at the window not under 15 degrees centigrade. If your seedlings turn out a little "longishly", it will grow together in next summer again. This time or in the early spring you can put the seedlings into a new substratum and larger pots. But you still have to wait for the splendid flowers at good care 3-4 years (Ornatum 5-8 years). Then the bishop's caps bring regularly and rich flowers from spring to fall. Your plants will get very old if you establish everything optimal. One knows that, for example, one hundred years aren't a limit in the life of an Astrophytum ornatum.