The bishop’s cap comes across as a not particularly exciting cactus. However, Astrophytum myriostigma has a lot to offer: a children’s cactus without thorns, pleasingly easy to care for if its most important requirements are observed and available in a surprising number of very differently shaped cultivars. Below you will find out what is important when caring for the desert cactus, why the name “bishop’s cap” comes from the surface and not the shape and much more.

This is how the bishop’s cap lives in nature

Bishop’s caps are desert cacti that grow in the arid regions of Mexico, mainly in the Chihuahuan desert (northern and central Mexico). This so-called rain shadow desert was created because the area is shielded from any rain front by the Sierra Madre.

In summer the temperature is around 30 °C during the day, around 20 °C at night, in winter 17 – 25 °C during the day, 2 to 5 °C at night and never below zero.

In the Chihuahuanian Desert, a bishop’s hat never sees or drinks more than 250mm of rainfall a year, most of it concentrated during the short mid/late summer monsoon season. For comparison: precipitation Germany annual average 1881-2014 = 754 mm.

The bishop’s cap in Mexico gets a lot of light: in Chihuahua there is an average of 7.7 hours of sun per day, in Germany 4 hours. Mexico is between latitude 14 and 30 degrees north (Chihuahua City 28, we between latitude 47 and 55 degrees north), so it is quite a bit closer to the equator than Germany. So the sun is a whole lot closer. All year round closer to the equator, the seasons do not differentiate so much into warm and cold. As if all of that wasn’t enough, the bishop’s cap has to be banished behind a window pane in winter so that it doesn’t freeze to death.

The Chihuahuan desert is a mountain-rock-scree desert, the bishop’s cap does not know a soil in the sense of our garden or forest soil. There is no humus-rich soil in deserts because there are hardly any plant parts that rot to form humus. At the same time, hardly any plant rot means that the organic nutrient content of the soil is very low, while the mineral nutrient content is very high.

This information will help a lot if you want to make a cozy home for a bishop’s cap in your living room:

The location claims of the bishop’s cap

From the point of view of a desert plant, the biggest difference between German living space and the desert is the light in which it is supposed to live here. In Chihuahua, the bishop’s cap gets much more sun than in Germany all year round, direct sun. With us, the bishop’s cap lives behind windows for at least part of the year. From the point of view of the plants, there is just “dark days”.

Therefore, the bishop’s cap should get a really light location, preferably the warm sunny place at the south window. And she should move outdoors in the summer, preferably on the sunny spot on the balcony where other plants get sunburned.

Our room temperatures are similar to average spring-summer-fall temperatures in Mexico, so quite familiar to the bishop’s cap. Outdoors, she enjoys every heat that Germany has to offer.

The bishop’s cap doesn’t need a lot of space here, it will be a maximum of 40 cm high.

Soil, substrate, planter

You should provide potted Astrophytum with soil similar to that found in the Chihuahuan desert. Cactus experts often keep desert cacti in purely mineral substrates, but this is not compulsory, cacti are really not spoiled. You can use cactus soil or normal (not freshly fertilized/over-fertilized) garden soil as a base for the mix.

This foundation is enriched with ground rock, so loose that the cactus can push roots through, so tight that the roots find footing and water doesn’t just run through. Any standard parent rock is fine, all contain minerals, preferably medium grain. Beware of primary rock flour, it is often excessively finely ground, fine particles tend to stick together to form “concrete”. You can get diabase, which is often the source rock for primary rock flour, from the nearest builders’ merchant. It then costs around €12 a ton. If you come by with the bucket they might charge you €1.2 for the service. You can also mix in aquarium sand, lavalite, perlite, all mineral grain mixtures.

Clay pots are suitable as planters. They have the advantage that excess water evaporates into the room via the outer wall. This is how cacti survive if you water them too much, which quickly happens to inexperienced plant caretakers. However, if it is very hot during the growth period, you have to watch the moisture in the clay pot carefully, as the substrate dries out faster.

The pot should not be too small. Cactus roots like to spread out flat to find a foothold in barren, rocky desert soil. A centimeter of space between the cactus body and the edge of the pot is the minimum. But you can also place the bishop’s cap in a flat flower bowl, perhaps with other cacti (with similar substrate and care requirements) as a small landscape. A drainage layer is put in the pot in front of the substrate, which keeps the drain free, e.g. B. from basalt split, clay pots should be placed without cover pots, because of evaporation.


As mentioned above, the bishop’s miter is used to a maximum of 250 millimeters of rainfall a year, most of which falls between July and September, which is the Astrophytum’s main growing season in Mexico. Here with us, the precipitation falls more evenly throughout the year, and part of the year the indoor gardener makes the rain anyway, the bishop’s cap puts its main growing season in the time with the most light, from May to August.

In this main growth period, the bishop’s cap should be watered, but moderately, please. The root ball should always be allowed to dry a little between waterings, water is only given when the top layer feels completely dry.


Plants live mainly on the four main nutrients carbon, hydrogen, oxygen, nitrogen and (much smaller amounts) of the main nutrients phosphorus, potassium, sulphur, calcium and magnesium. Except for water and nitrogen, which can only be used by plants in the soil/humus, the bishop’s cap finds all of these substances in abundance in the desert. When it comes to water and nitrogen, she has adjusted to being provided with rather meager supplies.

If the bishop’s cap is kept in soil rich in minerals, it does not actually need to be fertilized at all, at most when a flower starts to appear.

In cactus soil or normal potting soil, the bishop’s cap needs fertilizer, but then you should not give Astrophytum a normal complete fertilizer, but a fertilizer with little nitrogen, NPK 4-7-7 z. B., with trace elements. It is sold as cactus fertiliser, but you can also mix it yourself much cheaper in good specialist garden shops. Only fertilize during the main growth period, then at most once a month, and not too much.

make flowers bloom

Astrophytum myriostigma bloom, with beautiful light yellow flowers, which appear mainly solitary and only last a few days, but there can be several flowers from spring to summer (if you want to see a lot of cactus flowers, you should stick to the Astrophytum caput-medusae:

However, flowers do not develop until the third year, with us perhaps even later. And if the bishop’s cap gets enough light, i.e. at least stands outside in summer. The flowering period is between June and August, when you see the beginnings of flowers, you can already be ready with the smallest sip of flower fertilizer.

The flowers are hermaphrodite, pollination by wind or insects would certainly work, at least on the balcony – if you want to harvest seeds, you need two bishop’s hats, these are self-sterile, the pollen of a flower cannot pollinate the stigma of the same plant.


Our room temperatures would theoretically be fine for the bishop’s cap even in winter, in practice it is even colder on average in Mexico in winter; In addition, the bishop’s cap could suffer a silent death from a lack of light if it is to continue to grow normally in the winter.

Therefore the cactus should be sent into hibernation with us. After being cleared from the balcony, she is given a month of acclimatization at room temperature. Then the bishop’s cap is placed in a cool place, at temperatures between 4 and 12 °C, still in a light location, but not in direct sun, which would heat up the plants too much. During the dormant period, the bishop’s cap is not watered (if it is in the right place, it only evaporates traces of water) and of course it is not fertilized either.

The bishop’s cap stays there for at least 4 months, usually from October to March. This calm is also important so that the bishop’s cap can blossom. From March the bishop’s cap is slowly watered, in April it gets used to the sun and from May it is placed in the summer quarters.


Astrophytum only needs to be repotted every two to three years. In taller pots, the roots often already reach the edge of the pot, from which the bishop’s cap is potted out, the root is treated – dead parts removed, checked for pest infestation, combated if necessary – and then held vertically in the new container, which is already equipped with a drainage layer, while Bring in the substrate all around.

You should do the repotting at the end of the dormant period, then water slowly and carefully as usual. If you have had to cut a lot of fine roots, you should wait two weeks before watering, then the cactus has to form new fine roots with which it can absorb water.


The bishop’s cap is usually propagated by sowing, which should be started in the spring. The seeds are sprinkled onto the mineral-rich substrate mix described above and watered lightly. In an environment with high humidity and temperatures around 25 °C, they usually germinate after a few days.

Almost nothing can be found about propagation by offshoots, at most it is mentioned as not possible. With some cultivars of the bishop’s hat, however, it is certainly worth trying to cut and root cuttings.

varieties and species

The bishop’s cap is botanically called Astrophytum myriostigma, belongs (of course) to the cactus family, which in turn (not so naturally) belongs to the order of the carnation-like ones.

However, within the largest subfamily Cactoideae (100 genera, 1500 species), the bishop’s cap belongs to the tribe Cacteae, which has decided not even to develop the few sparse leaves that would be due to a “carnation-like” plant, but to do without leaves altogether. Out of necessity, because of thirst, and so it was with all 25 species of Cacteae (in case you’re getting annoyed by another rain shower).

The genus of the bishop’s cap is called Astrophytum, translated “star plant” after the star-shaped ribs of the first discovered Astrophytum ornatum, from which the bishop’s cap has meanwhile taken the “nickname” star cactus. It is called “myriostigma” after its innumerable (Greek myrios) spots (Greek stigma), which Astrophytum myriostigma developed instead of thorns. It comes in a variety of cultures:

  • The “normal” Astrophytum myriostigma has 5 to 8 ribs and instead of thorns, it has tiny, light-colored wool flakes.
  • Astrophytum myriostigma ssp. quadricostatum forms a body with four ribs, looks a bit like a children’s pinwheel from above:
  • Astrophytum myriostigma var. tricostatum forms only three patched ribs
  • A. myriostigma var. nudum is completely bare, no thorns and no tufts of wool on its normally five ribs.
  • A. myriostigma cv. TAO (forma bicostata) has only 2 ribs, which he twists merrily into each other, can be viewed at, Cactus curiosities, Cactus Curiosity No. 9

In addition to Astrophytum myriostigma, the genus includes 4 other species, which focus on point design (Astrophytum asterias,, miniature horns (Astrophytum capricorne, File:Astrophytum_capricorne_4.jpg), tentative attempts at grass (Astrophytum caput-medusae, or ornamental forms (Astrophytum ornatum, http://www.llifle. com/photos/Astrophytum_ornatum_cv._Spiral_16943_l.jpg ).

The rather unexciting bishop’s cap is also unexcitingly easy to care for if you know the decisive factors, but on closer inspection it already reveals a few surprises in terms of shape. For the curious, the Bischofsmütze has even more to offer. In some culture forms, plenty of sprouts for propagation attempts, kept in pairs for seed production to get started with cactus breeding. In addition, it is also a treasure trove for naturopaths. It is said to have an aphrodisiac effect and is said to have a positive influence on potency, hormone balance, high blood pressure, poor memory and many other weaknesses in the human body.

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