Gymnocalycium
Commonly Uncommon
This genus is both immensely common (think purple moon cactus, or the neon colored grafted cacti you see at big box stores), and incredibly underrated. There’s so many more species than just the moon cactus you can get from the store down the street.
One of the common names for the genus is “chin cactus”, which is kind of amazing. The reason I started collecting gymnocalyciums is in part because the idea of having a chin garden was enormously entertaining to me.
There are over 70 species in cultivation if you listen to Wikipedia, but Llifle, my favorite cactus encyclopedia, claims 170 types with 6 that are now classified as other species. When looking through the Llifle listings, they seem to be counting each subspecies or variety as a different plant, while Wikipedia… has limited sources, and seems to be just focusing on named species rather than subspecies.
The latin name “gymnocalycium” refers to the flowers having no hair or spines – the name translates, roughly, to “naked covering”.
So in addition to having a garden of chins, you can have a garden of naked covering chins. What’s not to love?
Conditions in situ
The popular cultivated species are common because they are hardy, easy to care for, and forgiving. With so many species that cover such a range of area, there are no hard and fast rules for every single species in the genus.
However, most are tolerant of light frosts (32F for very brief periods), and do best in warmer weather.
They are easy to encourage to flower, and generally stay small.
Location in the wild
Gymnocalycium are found throughout Argentina, part of Uruguay, through Paraguay, southern Bolivia, and parts of south Brazil. The map below is VERY approximate, and shouldn’t be taken as precise by any means. It should, however, help give you an idea of close to where these little sharp chins come from.
Gymnocalycium mihanovichii
In the wild, these are found in Paraguay, in the Chaco Boreal region. They grow under other plants and bushes, and don’t typically get much in the way of direct sunlight. There are numerous varieties or subspecies of mihanovichii, and notably, one of the ways to tell them apart is flower color. Mihanovichiis have pale green to brownish yellow blooms which don’t fully open, and mihanovichiis are more commonly grayish green with white and red blushing/highlights. Friedrichiis (what is more commonly available in cultivation) are distinguished by their purpley-pink, fully opening flowers. Gymnocalycium friedrichii is sometimes lumped with Gymnocalycium stenopleurum, although it appears that they may just be regional variations of a single species. If you’re interested in this difference between the different varieties/subspecies/species, I encourage you to learn more here at Llifle.
In Cultivation
These are enormously easy to grow if you have light and warm summers. If it’s cold in your region in winter, just bring them inside and keep them by a bright window. If kept dry, they can tolerate drops down to freezing or slightly below, but if you want them to thrive and look beautiful, keep them warmer than that.
Mihanovichii and friedrichii are summer growers which are quite happy to bloom in summer, especially if fed with a high potassium fertilizer a couple times during the growing season. Lots of sunlight encourages the deep purple coloration as well as spine growth, but protect from sudden changes in lighting or from full sun during particularly hot days or they’ll scorch.
These cacti stay small, are easy to care for, and are excellent if you’re just getting started keeping cactus.
Gymnocalycium andreae
In the wild, these are found in South America, as a small clumping cactus with tiny little spines. While most information online seems to indicate that these are normally round, green cacti that get a darker green with sun stress, I have found them to turn mildly blob-like and blush a deep, dark purple. Happier andreae cacti do not look like this.
Produces large yellow flowers in late spring through the summer months.
In Cultivation
These are enormously easy to grow, although for best appearance, try not to abuse yours quite as much as I’ve abused mine. Each cactus body seems to stay small, and produces offsets rapidly and with gusto.
They start to bloom in the spring, and will continue to make buds and flowers through summer, produce a prolific amount of seed.
Plant in a well draining cactus/succulent soil, potentially amending with additional pumice if your soil leans to having more organic matter in it. Expect to repot them every 2 to 3 years to refresh their soil, but otherwise, they are fairly easy growers.
While the internet says they are not at all cold tolerant and should be kept above 40F, I’ve found if they are kept dry, they tolerate night time air temperatures down to 30F. They should be protected from actual frost, but otherwise, they are equally as hardy as other gymnocalycium species.
That being said, I’d keep yours more protected than I have kept mine, just so they look like cacti and not blobs.
Gymnocalycium lukasikii
Originally, I purchased this distinctly labelled as “tukasikii”. While the grower I purchased these from is extremely knowledgeable and well respected in our local community, it is also fairly odd to see absolutely no mention of the latin name anywhere online.
After some sleuthing, along with help from the lovely @cocoageekplants on Instagram, I discovered that the latin name is actually lukasikii.
In Cultivation
I grow these nearly identical to the way I grow my andreae, and unlike the andreae, they did not turn into blobs with sunlight and water and warm weather.
Protect from a hard frost, but otherwise, these have been fine with air temperatures down to 30F. Keep dry when it’s cold out. Keep shaded if it’s the hottest part of the afternoon.
Gymnocalycium cardenasianum
AKA Gymnocalycium spegazzinii ssp. cardenasianum
Small, extremely slow growing species of Gymnocalycium that originates from Bolivia.
They are a solitary species, growing as a gray-green lump with pronounced spines that are heavily curved. Top is usually slightly indented, or concave, and very rarely (if ever) offsets with pups.
Blooms with funnel-shaped, pinkish flowers, supposedly, but mine have not bloomed yet – this may be due to time of year, as they most commonly bloom in mid summer and my other species have started in mid to late spring. It is common that flowers do not fully open due to the dense spines.
In Cultivation
These should be grown relatively hard for best spination, which means lots of sun (nearly full sun exposure). During the hottest period of summer, some protection from the worst of the heat is ideal, and mine are in a spot that gets sun at nearly all times except for around noon to 2 pm.
Keep dry in winter, and they will tolerate temperatures down to freezing.
The internet tells me they prefer acidic soil medium or they will eventually stop growing altogether; I plan to repot mine with a mix of acidic soil (for azaleas) and a heavier component of pumice and orchid bark to compensate for the moisture retention in the organic medium. Mine have continued to grow (you can see new, darker spines on top in the plant pictured left), but slowly, as noted, although our tap water is highly alkaline and comes from the hose at pH 8 to 8.4, depending on the day.
Gymnocalycium denudatum
Globular green cactus from a large range in South America, ranging from Brazil to Aregentina, Paraguay, and Uruguay.
Synonyms include
- Echinocactus denudatus
- Cereus denudatus
- Gymnocalicium paraguayense
Mature specimens can reach up to 6″ across, and 4″ tall. Produces large, creamy white flowers that can be nearly as wide as the plant when fully open.
In Cultivation
Extremely hardy and easy to grow cactus whose growing season is summer. Keep moderately well watered in during warm weather and long days. Does best in full sun in moderate climates, needs partial shade for southern growers with more intense sunlight. I keep mine in roughly 50% shade with full sun exposure in the morning and late evening.
Feed with a high potassium fertilizer in summer if desired.
If kept dry in winter, can readily tolerate temperatures down to 28 – 30F.
Gymnocalycium horstii
Distinctive, plump cactus with minimal spines and a green, round body. Occasionally called the spider cactus, but more commonly the tomato cactus due to the similar shape.
Found on rocky outcrops in the grasslands of Uruguay, Paraguay, south Brazil and Northeast Argentina. Wide range, but very scattered populations.
In Cultivation
Summer grower that thrives with regular water during the hot summer months. Enjoys more water than the average cactus, but should still be allowed to dry before being watered again.
Does not do well in hot, direct sun, and will burn if exposed to high sunlight coupled with heat – as I’ve experienced! If slowly acclimated to more intense sun, they will blush a bronze-brown color.
Rarely produces offsets and usually can be propagated through seeds. Blooms with large, white to deep pink flowers that are quite attractive.
Gymnocalycium amerhauseri (amerhausii)
A small, single headed little cactus found in Northwest Argentina in a small provence. Population size in the wild is estimated at fewer than 250 individuals!
Dark green body with short spines that look almost spider-like.
Flowers readily from summer through autumn, with creamy white to pale pink blooms with a redder hued center.
In Cultivation
Prefers plenty of space for roots and a relatively acidic soil. These are some newer gymnocalycium to my collection, and I have only had them a few months. They’re growing well in my greenhouse, showing the nice deep green of the body with attractive minimal spination and at first, a hint of blooms. The stress of shipping and rooting seems to have stunted any efforts the cacti were making to bloom this year, but I am hopeful for blossoms next summer.
These stay very small, and the plants I have are about as tall as these are normally seen, and may get somewhat wider with time.
The internet says these can be quite hardy to cold temperatures if kept dry in winter, but I haven’t experienced that season with these yet (2021). Through summer, they have thrived with plentiful water during the hot and sunny days.
Gymnocalycium anisitsii (ssp. damsii)
Slowly clumping cactus that flushes a brilliant magenta-pink when stressed by lack of water or sun exposure. They’re easy to grow, surviving a surprising amount of abuse and managing to still look pretty and pink doing so. When kept with regular water, good light, and a touch of fertilizer, they’ll happily bloom all summer long.
The photo at left has the label “gymnocalycium rotundum”, but that’s not an accurate name.
In Cultivation
As with most Gymnocalycium, pot in a well-draining soil mix, preferably one that’s about 50% inorganic materials, such as pumice.
Keep them in pots only somewhat bigger than they are, with the cacti rarely needing to be potted in something larger than a 5″ pot. Exceptionally old specimens that are clumping profusely benefit from a larger pot, but by that point, you’d likely already know what to do.
Surprisingly hardy to cold winter temperatures, tolerating drops to the high 20s if kept dry in winter. In summer, they will put up with just about any high temperature you can expose them to if kept well-watered. During particularly hot summers, take care to water only in the evening or first thing in the morning to prevent scorching or burning.
They will happily accept a dilute, balanced fertilizer during the growing season, especially in highly inorganic soil mixes or if it’s been over two years since you last re-potted the cactus.
MORE COMING!
