Many people love the Astrophytum myriostigma and its lack of spines (and many cultivars), but there’s a different cactus in the Astrophytum genus that holds my heart: Astrophytum capricorne.
There are, as with the myriostigma, many cultivars and clones of this species. They are easy to breed, flower and set seed readily, and respond well to selection, meaning there’s bound to be at least one that strikes your fancy. For my region in San Diego, they are quite possibly the perfect cactus to grow: they love heat, sunlight, and minimal water, and produce huge showy blooms all through the hottest months of the year.
What’s not to love?
Description and Natural Location
These distinctive looking cacti are native to Northern Mexico, and quite widespread through the Chihuahuan Desert. Their level of distribution means there are numerous locality types, ranging from heavily spined, white and wooly, thin spines, almost no spines, you name it.
The plant at left is from a private collection, but shows how incredible these cacti can be with time and good care. If you have hot summers, these cacti are great as long as you can keep them adequately dry.
When I say there’s a ton of cultivars and possible appearances for these cacti, I mean it! You can find these with a ton of white spots on them (like above), some with none, some with fluffy areoles, thick spines, thin spines, fat growing, tall growing… And with all the variety, even the big ones, they don’t require much in the way of root space.
Potting and Soil
These cacti do best in very well draining soil – I mix at least 50% pumice into my soil, although I know other growers often pot with up to 75% pumice. You want to use pumice or a similar porous material to ensure there’s enough aeration around the roots, and to encourage rapid water absorption/evaporation. These do not like having soggy roots and wet feet, so well-draining is essential!
A regular cactus/succulent mix works fine for these, although if you only have access to regular houseplant soil, mix with 75% pumice and you’ll be set.
Pot your Astrophytum capricorne in a pot only slightly bigger around than it is. If you’ve got a seedling (like one of mine from my newly published shop!), a 4″ pot is likely fine. Once they reach about 4″ across as young plants, you can pot them up into a 6″ pot and be set for a couple years.
Watering your Astrophytum capricorne
Water when dry in summer, which can be as often as every few days in a very hot and dry climate! More often, expect to water about once a week in summer, and not at all through winter.
In summer, it’s hard to over-water these if you have nice hot temperatures. When our area is averaging 90+, or even 100 degree days, I’d give mine more water, and for a couple reasons:
- I want them to get big, quick, for showing (the opposite of “hard grown”)
- I want them to bloom and bloom often so I can get seeds!
Fertilization and Alternate Growing Options
If you’re in the southwest, you can consider growing these in-ground! I had several in-ground for about two years, and they did extremely well (pictured above). Crucial elements are ensuring that it’s hot and bright enough for them and that the soil is well draining.
In ground, you don’t need to worry about fertilizer. The soil and nutrient exchange in a large area of ground is superior to anything you can try and provide.
In pots, these do well being fertilized with a dilute 1:1:1 fertilizer (half strength) every other time you water.
You should only fertilize in the hot growing months, late spring through summer. As the days get shorter for the fall season, cut back on fertilizer (or stop entirely) until you go completely dry for the cold winter months.
You can’t over-expose these to sunlight, to be honest. They love full sun, they love heat, and they thrive in it. I had several in pots sitting in full sun on my brick retaining wall, with roots and plants hitting 100F+ all summer, and they were SO HAPPY. They bloomed constantly, grew rapidly, and overall were super happy. Having them on that wall was how they captured my heart – they did amazing in conditions that absolutely cooked just about every other plant I’d ever tried growing along that wall.
BUT. Be careful with newly acquired plants, such as those shipped to you, or picked up from a nursery. You should slowly acclimate them to full sun in your region, or risk sunburn.
Blooming and Pollination
I adore how huge, brilliant, and gorgeous the blooms are on these cacti. I have several species of Astrophytum, and the blooms on these are honestly my favorite. They’re huge, often bigger on top than the plant is wide, and beautiful. Brilliant yellow flowers with a deep red throat and plentiful pollen.
In addition to being beautiful, these are extremely easy to pollinate. So easy, in fact, that they often cross-pollinate with any other astrophytum you have outdoors.
When buying my seedlings, they’ll either be indicated as open-pollinated or listed as hand-pollinated myself. Open-pollinated means the plants were outdoors, and bees, butterflies, and hummingbirds are the most likely pollinators…and that they are probably hybrids of some kind.
Hand-pollinated means I had them blooming in my greenhouse, protected from external pollinators, so I could tightly control the pollination. I use the hand-pollination method to cross my variegated A. capricorne with my others and know for certain what I’ve crossed.
Variegation from seed
My variegated capricorne is the most robust variegated Astrophytum I grow, and I cross it with all of my other non-locale specific capricornes.
Doing so, and growing the seeds, has shown me how many you have to grow to get more variegation! I sowed a few hundred seeds last year, saw about 1/4 come up variegated – but only 5 were robust enough to survive a year.
I do offer seeds for sale, but be aware they’re not guaranteed and can be weak seedlings! Even then, growing from seed is likely the most cost effective way to try and get your own variegated capricorne.
Sowing these and growing from seed follows the same process outlined in my Astrophytum asterias care diary.
Growing Astrophytum capricorne for shows
As seen above, when you grow your Astrophytum in a greenhouse and don’t rotate it for many years – they grow in an impressive spiral.
That growth habit is from staying oriented in the same place, facing the same direction, and the growth point following the sun through the seasons. When rotated, they often grow with the spines facing straight along the sides, and you get less of the clockwork spiral.
For the best consistent growth, size, and impressive nature, you can try growing them in-ground until they’ve reached a suitable size for showing (5+ years). You’ll want/need to consider methods to shelter the cactus from weather extremes, pests, and debris hitting the body of the cactus. A tripod with chicken wire, for example, can work to help deflect hail, leaves, or larger items blowing or rolling onto the plant.
Grow your own!
Check the shop for when my seeds become available, and try your own!
You can follow along with me on Instagram @TrexPlants, and see when I pollinate my flowers and when I harvest the fruit. I’m sowing my 2023 seeds now (February – March), and you can expect my first batches of 2020 sown seeds to be available this summer!