Cacti of the genus Astrophytum (Star Cactus)


Growing cacti is becoming more and more popular among flower growers. Among the variety of such crops, they try to choose only the most interesting and unpretentious in care. An amazing plant – Astrophytum cactus – is popular. We propose to get acquainted with the features of this cactus, the rules of care indoors.

Features of the genus Astrophytum

The genus Astrophytum includes six species of cacti native to Mexico and the southwestern United States. Three of them are cultivars, better known by the common designation “star cactus”. The name was given for their ribbed structure, resembling the shape of a star. The trunk of Astrophytum is covered with areolas on which there are sharp black or golden spines. In some species, a white phlox grows on the surface of the body, designed to protect the plant’s tissues from the sun.

Astrophythum in natural conditions
Astrophythum in natural conditions

The main feature of such a crop is felt speckles in light shades, which are evenly arranged on the surface. These “dots” perfectly absorb water. There are varieties of Astrophytum with large prickles on the surface.

In translation, the name of the plant means: “astro” – “star” and “phytum” – “plant”. There are quite a few varieties of astrophythum that grow indoors, and they are very popular with florists. Most varieties have a proportionately rounded trunk, with both weakly and strongly pronounced ribs.

It is worth knowing that Astrophythum is quite slow to develop. Its flowering begins in early spring and lasts until late fall. The florets are usually large in size, colored in a yellow shade with a reddish yawn on top. The florets are attached to the stem tip. Once they open, they are beautiful for 2-3 days, after which they fade.

You can see the incredible shapes and colors of cultivars of the genus Astrophytum and enjoy their blooms by watching this video.

Astrophytum asterias are highly prized by plant collectors. But they are very difficult to propagate.

Care of Astrophytum indoors

Astrophythum has similar care needs as other cacti with a few nuances. Let us tell in more detail about the growing of this wonderful plant.

What type of soil is right for the cactus?

Like most cacti, Astrophythum prefers stony and sandy soils. Astrophytum prefers acidic soil with a pH of 5 to 6.5.

Astrophythum collection in the greenhouse
Astrophytum collection in the greenhouse

You can find a large selection of ready-made cactus and succulent potting soil mixes at the store.
Our plant needs a light potting soil, but it should not contain too many nutrients and organic matter. To prevent rot you can add a small amount of shredded charcoal into the soil mixture. Astrophytum substrate is best suited with a pH of 6.0.

Remember that the stagnant moisture in the soil mixture can kill the plant. Therefore, make a good drainage layer, the thickness of which should be equal to a third of the height of the pot. To do this, use fragments of red bricks or expanded clay. After planting the cactus, the surface of the substrate is also backfilled with drainage material, for example, small pebbles. This will help prevent the accumulation of liquid at the root neck.


Star Cactus belongs to the light-loving plants. You should choose a place with a lot of bright light. A window facing southeast or south is perfect for the plant. In the summer heat, when the sun’s rays are most intense, Astrophythums should be moved to a shaded area. In winter the cactus does not need extra light.

Temperature and humidity

Optimal growing temperatures are between 68 and 77 °F (20 and 25 °C). It is recommended to provide a difference between day and night temperatures. To do this, the pot with the flower can be taken to an open loggia or terrace, leaving it at night. Astrophythum should be kept indoors at approximately 50 °F (10 °C) during the winter.

Star Cactus feel great in the summer period
Star Cactus feel great in the summer period

The cactus responds well to low humidity in the room. It is not necessary to humidify it with a sprayer. However, the plant needs a regular supply of fresh air, so do not forget to ventilate the room where it is located systematically.

Remember that high air humidity in the winter months can kill the cactus by rotting.


Proper watering for Astrophytum is the main and important point in the care. The cactus should be watered moderately in the summer. The soil should be fully saturated with moisture and the substrate should then dry well.

Remember. Star Cactus stop their growth during the growing season during the day. Active moisture absorption begins with the onset of darkness. Therefore, water the plant in the morning or in the evening after 6:00 pm.

Experienced cactus growers often use bottom watering. From autumn to spring, water cacti infrequently. One or two waterings over the winter will serve the plant well.


Astrophytum fertilization is done with a purchased cactus fertilizer that can be purchased at a specialty store. Fertilizing is done in spring and summer with a frequency of once every 4 weeks. However, you should use ½ of the dosage recommended by the manufacturer to prepare liquid fertilizer. No fertilizing is carried out during the winter.


The Star Cactus needs regular transplanting. Astrophytum should be transplanted at the beginning of each growing season to allow it to grow to an impressive size. Prepare a clay or terra cotta pot with wide drainage holes.

  • Fill the pot with a well-drained cactus mix.
  • Remove the plant from the pot and move it to a larger pot.
  • Fill the pot with the potting soil mixture.
  • Water the plant and allow the water to drain completely.

Fertilizing is best done after a few weeks as replanting the cactus can stress the plant.

Succulent care information

How to propagate Astrophytum cactus

The star cactus does not form offspring, so only seeds are used for propagation. They are quite fragile, so handle them with care. Seeds have a fairly short shelf life. It is best to plant them after harvest to have success on rooting. Before planting, it is worth soaking the seeds overnight. Next, do the following steps.

Astrophytum sprouts
Astrophytum sprouts
  • Fill the tray with cactus growing mix and place the seeds on the tray.
  • Press them slightly into the soil mixture and cover the top with a thin layer of soil. The soil should be moistened.
  • Cover the tray with a plastic lid to retain moisture.
  • Place the container with the seeds in a sunny window, keeping the temperature at 70 degrees Fahrenheit. Provide systematic ventilation for the seeds, and remember to moisten the potting soil regularly as the top layer dries out.
  • The first shoots should show after 7-15 days. After that, open the tray and gradually acclimatize them by increasing the periods of exposure to direct sunlight.
    Once the seedlings have grown and become like small balls, they should be carefully unpacked into individual small pots.

Diseases and pests of Atrophytum

The cactus is often attacked by mealybugs, spider mites and scales.


Usually appear as white tiny fuzzy dots, more like small cotton balls. They slowly suck the sap of the plant. If you find the pest, spray the plant with a jet of water. Alternatively, medical alcohol and water can be used. Use some absorbent cotton to apply the diluted alcohol to the affected areas.

In addition to sucking sap, mealybugs can eat the roots of the plant. This is where you will notice that the plant becomes unhealthy, even when outwardly everything is fine. In this case, you will have to pull the plant out of the soil and check the roots. If you notice tiny creatures, rinse the roots well and repot them in a new pot (or thoroughly wash the previous one) using fresh soil mix.

Spider mites

They’re pretty good at hiding, so you won’t notice them until your plant is affected. Brown spots on the surface are a sure sign of their presence. To get rid of them, simply use the water spraying technique described above or rub with alcohol mixed with water.


These pests usually have a tough exterior coating. And they are not as easy to wash off as worms and mites. Mechanical cleaning is quite effective (manually remove the pest with a toothpick).

How to avoid Astrophytum root rot

This is an obvious problem if the plant gets too much water or the soil mixture drains too slowly. Adjust the frequency of watering and watch how the soil lets in moisture.

Common species of Astrophytum cactus

There are six main species of the genus Astrophytum and many artificially bred varieties – cultivars. We propose to consider the most popular varieties in more detail.

Astrophytum asterias (sand dollar cactus, sea-urchin cactus, star cactus, or star peyote)

Very common among florists because of its ideal symmetrical shape. The stems have no thorns, on them there are 8 ribs of flat shape.

Astrophytum asterias
Astrophytum asterias

Despite the slow development of the plant, it is capable of reaching up to 7 inches (18 cm) in diameter. The cactus blooms yellow. For propagation, the seed method is used. The most popular variety is considered Super-Kabuto. Its peculiarity is that it can either be completely covered with mottling, or not have it at all.

Astrophytum myriostigma

This species is commonly referred to as bishop’s cap cactus, bishop’s hat, or bishop’s miter cactus. The variety is considered the most unpretentious, thorns on it almost completely absent, but there is felt speckles of white hue.

Astrophytum myriostigma
Astrophytum myriostigma

The large ribs are usually no more than 5, the flowers reach a diameter of up to 2 inches (6 cm), they have a yellowish color, sometimes you may find a reddish-orange callus.

Astrophytum capricorne (Goat’s horn cactus)

Young cactus are usually round in shape, with time they turn into cylinders. The cactus is up to 6 inches (15 cm) in volume and no more than 10 inches (25 cm) tall. Usually count up to 8 ribs.

Astrophytum capricorne
Astrophytum capricorne

Such a strange name for the cactus because of the presence of interesting curved barbs, visually resembling goat horns. The stem is a dark green shade, it has many speckles of light color. The florets are yellowish in color.

Astrophytum ornatum (Bishop’s cap or monk’s hood cactus)

Characterized by a large number of thorns, usually up to 6 ft (2 m) in height. But when grown indoors, it does not exceed 8 in (20 cm) in height.

Astrophytum ornatum
Astrophytum ornatum

The surface is covered with felted stripes (speckles) that create interesting patterns.

Astrophytum caput-medusae

A rare plant, an endangered species. Its appearance does not resemble other plants in the genus. Astrophytum caput-medusae

Instead, it has narrow, cylindrical stems up to 7 in (17 cm) long with yellow flowers. This species is rarely grown as an indoor plant.

Astrophytum coahuilense

Another rare species, almost never grown in greenhouses. Very similar in appearance to A. myriostigma, with five ribs and similar size, but its body is a softer gray color. It grows in northern Mexico, away from its “relatives”. It is very demanding of intense sunlight and grows slowly. The largest cactus of this species reaches up to 2 ft (50 cm) in height and 8 in (20 cm) in diameter.

Astrophytum coahuilense

The stem of this species is globular when young, but over time it elongates into a column-shaped form, with no side shoots. The color of the stem is gray-green, and it is completely covered with a layer of grayish-white flaky speckles.


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