Astrophytum myriostigma or Bishop’s cap

Astrophytum myriostigma is an interesting and beautiful cactus that many exotic plant lovers have come to love. Its spectacular appearance, unique tubercles and ribs make it a standout in any collection. ‘Bishop’s Cap’ is a great choice for those looking for an easy to care for plant and an eye-catching addition to their home.

Classification and description of Astrophytum myriostigma

Astrophytum myriostigma, commonly known as Bishop’s cap or Star cactus, is a species of cactus native to central and northern Mexico. This species grows between 2500 and 5000 ft (750 – 1,500 meters) above sea level on stony, limestone soils. Its habitat is overgrown plains or steep slopes facing east or west.

Astrophytum myriostigma is relatively new to the cactus world, having been discovered in the late 19th century by German botanist Carl Moritz Schumann. It was first described in 1899 and has since become a popular ornamental in many parts of the world. In its natural habitat, the bishop’s cap grows in rocky desert areas, often in the company of other cacti and succulents. It is adapted to hot, dry conditions and can tolerate long periods of drought.

It is a small, slow-growing cactus that usually grows to 4-8 inches (10-20 cm) tall and 3-5 inches (8-15 cm) in diameter. It has a characteristic star shape with five to eight rounded ribs that form a pentagonal or hexagonal shape, depending on the plant. The ribs are covered with small white or yellowish dots called tubercles, which are actually modified areoles that release spines.
The spines of Astrophytum myriostigma are short, usually only a few millimeters long. They are usually curved or twisted, and their color can vary from white to yellow to brown. The spines grow from the edges of the tubercles, giving the plant an indistinct appearance when viewed up close. In the center of the plant is a small round depression known as an “eye” from which the plant’s flowers emerge.

Astrophytum myriostigma flowering

The flower emerges from areoles at the tip of the stem of a mature plant and is usually no more than 2 in (5 cm) in diameter and up to 3 inches (7 cm) long. Flowering lasts about 2 days. The flowers are yellow with a red or orange midrib and appear in spring or early summer. Despite the slow growth rate, with proper care, even young plants can bloom. The flowers of the cactus have a faint sweet odor. The fruits are up to 1 inch (2.5 cm) in diameter, greenish to brownish-red in color, covered with brown, overlapping scales with long wool in the axils.

One of the most interesting features of Astrophytum myriostigma is its ability to hybridize with other members of the Astrophytum genus. This has led to the creation of a wide range of varieties, each with its own unique appearance and characteristics. Some of the most popular varieties include Astrophytum myriostigma ‘Onzuka’, which has long, twisted spines, and Astrophytum myriostigma ‘Quadricostatum’, which has four ribs instead of five or six.

How to grow Astrophytum myriostigma indoors

Let’s describe in detail the conditions in which the ‘Bishop’s Cap’ will grow without problems and please the owner with its beautiful appearance.

Soil

This cactus prefers well-drained soil that is slightly acidic. You can prepare a soil mix of 2 parts sand, 1 part perlite, and 1 part peat moss, fertile soil, or coconut coir to help it grow well. Alternatively, you can use a quality ready-made cactus mix from a gardening supply store.

Lighting

Astrophytum myriostigma needs bright, direct sunlight for at least 4-6 hours per day. Do not overdo it with light – do not expose the plant to direct sunlight for long periods of time, especially during the hot part of the summer day. To grow the cactus indoors, place the pot with the plant near a south-facing window.

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Temperature and Humidity

“Bishop’s cap” prefers warm air between 70-80 °F (21-27 °C). It can tolerate temperatures as low as 50 °F (10 °C), but only for short periods. It is a desert plant and does not like high humidity, so avoid placing it in humid areas.

Water

Allow the soil in the Astrophytum myriostigma pot to dry out completely before watering. Water the plant once a week during the growing season (spring through fall).

In winter, reduce watering to once a month or less. Excessive watering can cause root rot and kill the plant. And ‘Bishop’s Cap’ is very susceptible to this disease.

Fertilizer

Astrophytum myriostigma does not need much fertilization. To keep your plant looking healthy, you can fertilize your cactus once a month during the growing season. Be sure to dilute the fertilizer to half strength to avoid burning the roots.

Repotting Astrophytum myriostigma

Bishop’s cap grows slowly and does not require annual transplanting. This cactus likes to be confined in a pot. The plant should be transplanted when it outgrows its current pot. What to do.

• Select a new pot. It should be 1-2 inches (3-5 cm) larger in diameter than the current pot. Drainage holes in the bottom are a must to allow excess water to drain.
• Prepare the potting mix. Prepare the soil mixture as described above.
• Wear gardening gloves to protect your hands from Astrophytum myriostigma spines. Turn the pot upside down and gently tap the bottom of the pot to loosen the soil. Carefully remove the cactus from the pot by holding the base of the stem.
• Inspect the roots for signs of damage, rot, or pests. Trim away any dead or damaged roots with clean, sharp scissors or pruning shears.
• Place a layer of potting mix in the bottom of the new pot. Hold the ‘Bishop’s Cap’ in the center of the pot and fill in the potting mix around it, making sure the cactus is upright and standing. Press the soil lightly with your fingers to remove any air pockets.
• Moisten the soil well with water. Allow the water to drain from the pot and discard the excess water in the saucer. Do not water for one week or until the soil is completely dry.

How to propagate Bishop’s Cap

Astrophytum myriostigma can be propagated in two basic ways – by seed and by grafting. We will describe how to propagate the cactus by each of these methods.

Propagation by seeds

The best option is to obtain fresh bishop’s cap seeds from a reputable source.

• Sterilize the seed potting soil by baking it in the oven at  200 °F (93 °C) for 30 minutes.
• Fill a small pot or container with the sterilized seed mix.
• Moisten the mixture with water so that it is evenly moist but not overly saturated.
• Spread the seeds evenly over the surface of the mix and press lightly into the soil.
• Cover the container with a clear plastic lid or film and place in a warm, bright location out of direct sunlight.
• Check the container daily and water the soil lightly as needed to keep it moist.
• Seeds should germinate within 2-4 weeks. Once they have germinated, remove the plastic cover and place the container in a bright, sunny location.

Allow the seedlings to grow for a few months before transplanting them into individual pots.

Propagation by offshoots

Wait for Bishop’s Cap to produce suckers – small shoots that grow from the base of the mother plant.

• Carefully separate the cuttings from the mother plant with a sharp, clean knife or scissors.
• Allow the cuttings to dry for a few days in a warm, dry place out of direct sunlight.
• When the cuttings are blistered, fill a small pot or container with well-drained cactus potting mix.
• Plant the cuttings in the soil, making sure the base of each cutting is in contact with the soil.
• Water the soil lightly to allow it to settle and place the pot in full sunlight.
• Allow the cuttings to root and grow for a few months, then transplant them to individual pots.

Propagating Astrophytum myriostigma is a slow and delicate process that requires patience and attention to detail. However, with the proper care and conditions, you can successfully propagate this beautiful cactus plant.

What problems can occur when growing Astrophytum myriostigma?

Here are some of the most common problems with Astrophytum myriostigma and how to solve them:

• Overwatering. Bishop’s cap is susceptible to root rot if overwatered. Wait until the soil is completely dry before watering again. Water deeply but infrequently and avoid getting water on the stem.
• Sunburn. Although Astrophytum myriostigma needs plenty of sunlight to thrive, it can become sunburned if left in direct sunlight for too long. Provide the cactus with bright indirect sunlight or gradually acclimate it to direct sunlight over several weeks.
• Pests. The cactus may attract pests such as mealy bugs, spider mites, and scales. Check the cactus regularly for signs of infestation, such as sticky or discolored areas, and treat with an insecticide or garden oil if necessary.
• Nutrient deficiencies. Bishop’s cap may visually show signs of nutrient deficiency in the form of a yellowing stem or stunted growth. Fertilize your cactus with a well-balanced fertilizer during the growing season and be sure to follow the label directions.

Popular varieties and cultivars of Astrophytum myriostigma

At the moment there are more than 100 cultivars of this spectacular cactus in the world. Let us describe the most famous cultivars of Astrophytum myriostigma.

Astrophytum myriostigma var. nudum

It has no white spots on the stem and its epidermis is smooth. The stem varies with age from spherical to cylindrical in shape, 3 ft (1 m) in height. The number of ribs varies from 3 to 8 (usually 5).

Astrophytum myriostigma var. quadricostatum

This is a variety of Astrophytum myriostigma with four ribs instead of five. It is usually a solitary cactus with an almost spherical stem when young that becomes columnar with age. The stem reaches 3 ft (1 meter) in height and up to 10 cm in diameter. The flowers are pale yellow, 2 in (5 cm) long, and appear in spring and summer.

Astrophytum myriostigma ‘Onzuka’.

An attractive cactus with many white dots on the epidermis. The stem looks mottled because of these snow-white spots. The appearance of the spots may change as the cactus ages.

Astrophytum myriostigma ‘Onzuka Quadricostatum

This is a variation of the superior variety with four ribs instead of five and a white, heavily mottled epidermis with incredible markings. The stem is square to 3 ft (90 cm) tall. As the plant ages, it quickly takes on a cylindrical shape.

Source: gardenbeast.com