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A mature Astrophytum ornatum for sale at Tula Plants & Design. A mature Astrophytum ornatum for sale at Tula Plants & Design.

Astrophytum ornatum

Botanical Name — Astrophytum ornatum

Common Name — Monk's Hood, Star Cactus

Plant Family — Cactaceae


Background


Astrophytum ornatum is a columnar cactus native to Central Mexico. Early in its long life, this plant will look spherical, calling to mind a small barrel cactus, but as it grows, it matures into a thick cylindrical column, up to six feet tall. Remarkably hardy, Astrophytum ornatum is one of the most drought-tolerant plants in the world, even among cacti. Look for large, yellow blossoms in spring and summer that have a sweet scent.


Growth Requirements


Sun

  • These cacti prefer lots of sun, at least five hours of direct sun daily. They can tolerate a little shade, but the more sun the better.
  • Indoors, a south facing window is ideal. Outdoors, give them a place where they will get plenty of sun exposure.

Temperature/ Humidity 

  • Astrophytum like it hot! Above 70 ºF in the summer is preferred. But since these plants are native to mountainous areas of Central America, they are also accustomed to seasonal cool weather. 
  • During the winter they prefer cooler temperatures, between 50 and 60 ºF. If grown outdoors, move them to a sunny windowsill inside in regions where temperatures regularly drop below 50 ºF.

Water

  • Astrophytum prefer to stay on the dry side. In the summer water them only when the soil has dried out entirely. Always error on the side of underwatering. They are built to withstand drought, and overwatering is one of the quickest ways to kill them.
  • During the winter, water very infrequently. Maybe even once a month or month and a half. It’s safe to cut back on watering entirely. This will encourage flowering during the spring!

Soil/Roots

  • Astrophytum are native to rocky, mountain slopes and a desert climate. They prefer a gritty, well-draining soil mix. A cactus mix works fine. You can amend it with sand or fine pumice up to 50% to improve grittiness and drainage. 

Flowering

  • Astrophytum ornatum will produce one or more flowers between spring and summer. Look for wide, 6-10 cm in diameter flowers. They are a vibrant yellow with a sweet scent.
  • Astrophytum plants flower once they’ve matured. This can take up to six years. Exposing your cactus to drought while it is dormant during the winter will encourage blooming during the growing season. 

Fertilization

  • Typically, Astrophytum do not require fertilization. You can feed them during the active growing season to give them a boost or refresh their soil. Apply a balanced fertilizer diluted at half strength, once a month. Never fertilize in winter.

Propagation

  • Astrophytum are typically propagated by seed. Seeds are fragile and have a fairly short shelf life. Be gentle with them and sow quickly after harvesting to improve chances of germination. 
  • Very occasionally, these plants will produce offsets which can be separated and grown independently.

Health


Diseases

  • Astrophytums are not especially susceptible to pests or diseases. Keep an eye out for common pests such as aphids, mealy bugs, and scale. 
  • Root rot can be a common issue in the instance of overwatering. 

Maintenance (pruning, legginess, repotting)

  • Astrophytum plants are very low maintenance. They prefer to be pot bound. Repot them once every two to three years. Early spring is the best time to repot, when they are just waking from their dormancy. 

Toxicity

  • Astrophytum are not known to be toxic to humans or pets.