Plant Highlights
Plant Highlights By Date Plant Highlights Alphabetically
Plant Highlight: Astrophytum ornatum
by Brian Kemble
About the genus and area of occurrence
The genus Astrophytum is not a large one, with six species recognized in The New Cactus Lexicon, published in 2006. However, these plants are very popular with cactus growers and can be found in collections around the world. All the species occur in Mexico, with one occurring also in south Texas. The largest is Astrophytum ornatum, and it is native to the states of Queretaro and Hidalgo in east-central Mexico, farther south than any other species.
About the plant
As a young plant, Astrophytum ornatum is globose, with protruding ribs (ridges that run vertically down the body of the plant), along which the areoles are situated at intervals of a couple of inches (5 cm) or less. The areoles are the wooly points from which the spine clusters emerge, and later the flowers. The green epidermis is usually initially densely flecked with small white scales, giving the plant a speckled appearance, and later the flecks coalesce into horizontal bands that arch upward from the troughs between the ribs up to the rib summit. The spacing and density of these bands varies considerably from plant to plant, and they may diminish or vanish altogether in older specimens. There are between 5 and 11 spreading spines per areole, and these are up to 1.2 inches long (3 cm) and yellow, honey-colored or brown. A mature plant typically has 8 ribs, which may be spiraled or vertical, and a diameter of 8 to 12 inches (20 to 30 cm). With age, the plant becomes columnar, with older specimens reaching a height of 40 inches or more (1 m). Exceptionally large plants in the wild have been measured at up to 10 feet tall (3 m).
About the flowers and fruits
Astrophytum ornatum flowers from spring to fall, and although sometimes a solitary flower may open, usually the flowers come in bursts of several at once, with multiple weeks passing before another flowering event takes place. The flowers are yellow and 2.8 to 4 inches across (7 – 10 cm), opening during the day and closing at night for several days in a row. On some individuals, the flowers take on a pink tinge after the first day, becoming even more markedly pink on the third day. When pollinated, the flower’s petals wither while the base enlarges to become a rounded fruit, covered with scales and hairs on the outside. Although the fruit is not juicy, the seeds inside are sticky. At maturity, the fruit splits open at the top to reveal the seeds. From one side, each shiny black-brown seed looks like a tiny pear about .12 inch long (3 mm), but on the other side it is scooped-out, so that the seeds are like miniature caps.
Plants in cultivation
Although A. ornatum comes from a part of Mexico where the rainfall occurs mostly in summer to autumn, it can tolerate winter rainfall if the drainage is excellent. Note that in a Mediterranean climate such as that of California, it must be given occasional supplemental water in the summer and early autumn months, since so little precipitation comes at this time of the year. It can take full sun, half-day sun, or lightly filtered sun, but should not have excessive shade. It can be grown in a pot as well, kept in a greenhouse or in a sunny window and watered every week or two during its growing season. It can endure winter overnight lows down to the mid-20’s F (to -4° C), but not extended freezes.
