Astrophytum (2019)

By Pat Mahon (August 2019)

One very unusual cactus genus that blooms this time of year is Astrophytum. At the society’s summer show in 2017, there was a beautiful Astrophytum myriostigma that had an unopened bud that eventually opened up and bloomed in the sun on the show floor. This genus is known for large, silky-sheened, highly petalled flowers. They are gorgeous!

Astrophytum consists of only five accepted species endemic to the Chihuahuan Desert in Mexico and southern Texas. A. caput-medusae is still fuzzy on where it fits within the genus.

The name Astrophytum is derived from the ancient Greek “astron,” which means star, and “phyton,” plant, in an obvious reference to the majority of the species’ bodies having star-shaped forms. All these cacti share a very similar funnelform shape and a silky perianth (sepals and petals). Some of the species have spines, and some lack spines. Almost all have some sort of hairy scales covering the body or in beautiful patterns, and woolly areoles.

Nearly all astrophytums are considered easy to grow, and apparently are easy to propagate from seed. Each species is described below.

Astrophytum asterias. This species resembles a sea urchin, with many patterns of hairy scales in varying amounts. Completely nude examples also exist, as well as several types of variegation. These were once found throughout parts of Texas and seem to historically have had a wide distribution. These days, the distribution has been reduced to possibly 5.000 plants in one locality in Texas.

Flowers are silky yellow with red centers. The bodies are similar in shape and appearance to those of the attractive lophophora, and also form slightly tuberous taproots.

Astrophytum capricorne. One of the two species with spines, these seem to be very rewarding plants. Although seedlings are easy to find, they don’t get the attention they deserve from beginners. The plants are forgiving in cultivation and seem to be able to bounce back from whatever human error you throw at it.

As seedlings, they are tiny, spiny, ugly things. Fast forward a few years, and the plants begin to become more globular and sport the beautiful yellow flowers with red centers. In time, and if encouraged to grow a larger root system, they will begin to grow in a columnar manner. The long and wiry spines lower on the plant seem to fall off with age.

Astrophytum ornatum. The other spiny species, this one is a little more difficult to find in cultivation. The plants sport more organized, small and angry little spines on the areoles along the ribs. Personally, I find them the most beautiful plants in the genus. Most sport hairy scale patterns that become more dense in mottling at the apex of the stem.

Similarly to A. capricorne, A. ornatum begins globular and over time becomes columnar. Flowers are monochromatic, ranging from white to yellow.

Astrophytum myriostigma. One of the most common astrophytums encountered in cultivation, these present an endless supply of body shapes, color forms, variegation and amounts/patterns of hairy body scales. There are several subspecies that also sport incredible texturing on the bodies.

Many Japanese cultivars, such as Kikko and Super Kabuto, have become the most prominent trendy and expensive examples in the genus. Like the other four species, these eventually (and more quickly) grow to be columnar. Flowers range from silky white to yellow.

Astrophytum caput-medusae. The oddball species that doesn’t quite fit in the genus was also the most recently discovered (2001) from a small population in Nuevo Leon, Mexico, and possibly another department. These have typical Astrophytum flowers: funnelform, yellow and with woolly pedicels. Altough the tubercles are fingerlike, there is an areole on each, also covered in hairy scales.

The major difference between A. caput-medusae and other astrophytums is that the plant’s body is reduced to a cylindrical mass with paperlike bristles originating at the base of the tubercles. They also seem to have the development of a tuberous root system. A. caput-medusae does not hybridize with other species in the genus and seems to be difficult to propagate by seed.

Because these are still uncommon in cultivation, they are offered both grafted and on their own roots. Grafted plants will need adequate watering for the rootstock so tubercles do not dry and wither. If on their own roots, plants can withstand a little less watering due to the formation of the taproot. In any case, these cacti should be potted in a fast-draining mix, possibly supplemented with a little organic matter for a minimal amount of moisture retention.

Almost all Astrophytum species grow in the presence of other plants (i.e., agaves or bushes), which help shade their bodies from the intense sun and create organic matter in the root zone. Most of the species seem to enjoy watering during active growth, tapering down in the winter. In the case of A. caput-medusae, seedlings and mature plants seem to favor a little extra watering, possibly because of the reduced body size. It prevents tubercles from shedding.

Astrophytum is another genus of cacti in which all species seem to be good candidates for any level of cactus-growing experience. From other growers’ experiences, the seeds of all astrophytums – except A. caput-medusae – are easy to germinate and grow. They survive well through winter and hopefully will reward you with blooms in time for the next cactus show!

Sources:
Die Kakteen – Volumes I, IV: Astrophytum – H. Krainz
Wikipedia – https://en.wikipedia.org/wiki/Astrophytum
CactiGuide.com – http://cactiguide.com/cactus/?genus=astrophytum
Llifle Encyclopedia of Cacti – http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/1845/Astrophytum_myriostigma
http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/1464/Astrophytum_asterias
http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/3564/Astrophytum_capricorne
http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/3593/Astrophytum_caput-medusae