I have a bad habit of scrolling through Etsy or Instagram, looking for Gymnocalycium species I don’t have yet. These were from a seller that had quite a few Gymnocalcyium, all seed grown, and I decided to snag them even though I’d never heard of the species before. A quick google search told me that they should stay small, and their blooms should be quite pretty.
Quick Care Guide
Frost Hardiness: To 32F easily, if kept dry
Watering: Enjoys frequent (weekly or more) watering in summer
Light: Shade during afternoon; full sun otherwise
Soil: Prefers very porous, well-draining soil
In nature, these cacti are found in a small area in the Sierra Chica of Argentina. A handful of small distributions have been recorded through the Cordoba province, but they are far from common.
Only about 250 individual specimens are estimated to exist in the type locality, although they are somewhat protected due to their altitude and growth in undesirable grassland regions. That said, it is suspected to be more widespread than currently recorded, and is not considered threatened.
These small little cacti closely resemble several other Gymnocalycium, but they have some clear distinctions.
They’re small; rarely more than 1″ tall and 2.5″ across for what you can see above ground. There is typically a long lower ‘stem’ below ground, which is a part of the body, in addition to a long taproot or stake-like main root body.
Typically 8 ribs, flatter near the base of the plant and slightly more mounded near the top. Areoles in slightly raised lumps, with the areoles slightly depressed. New growth has yellowish to white fuzz covering the areoles, remaining visible in cultivated plants but described as rapidly disappearing in habitat specimens.
Flowers are large and impressive, with large white petals and a long throat that’s deeply reddish.
Growing G. amerhauseri
These little plants flower readily when young and stay small, making them exceptional for container cultivation.
I have grown mine well for the last couple years in a mix that’s 50% pumice, 50% cactus soil, with a layer of pumice on top for presentation.
As young plants just under 2″ across, they did well in 4″ pots, and they’ve become slightly larger. I potted one up into a show pot, and the other will get a soil refresh this spring, along with many of my other Gymnocalyciums.
Water and Fertilization
In winter, these should get very little to no water at all if you’d like them to be exposed to cold weather.
In summer, however, they’re easy keepers – they’ll accept plentiful water as long as it’s hot and bright. For best appearance, though, you should only water when they’re quite dry.
These cacti turn a very pretty deep burgundy when stressed, which can be due to cold, light exposure, or lack of water. This is worth monitoring as a signal, although what it indicates varies on the season.
Fertilizing your Gymnocalycium
These little cacti need very little in the way of supplemental plant food, and to keep them from becoming bloated or overgrown, should not be fertilized very much at all.
However, in spring, or if potted in a highly inorganic mix, they can definitely benefit from a light feed. I use a balanced 1:1:1 fertilizer at half strength every two or three times I water the cacti in spring, as long as the days are expected to be sunny for bit after.
As an example of how this plays out, this year (2023), we’ve had a lot of cloud cover and rain, so I’ve only fed for springtime once in the last month and a half. Last year, in 2022, it was hotter and sunnier, so I was watering and feeding every week or two.
The darker your lil amerhausi, the more stressed they are about something – and the most common reason is typically light exposure.
I enjoy mine the most when they have the deep reddish blush, so I prefer keeping them in a bright exposure. In my greenhouse, they’re in full sun with 40% shade cloth during summer. Their small size makes them easily shaded by the other plants, which protects them from the worst of the sun and heat when there’s a heat wave.
Keeping them in nice, bright sunlight exposure encourages spine production as well as prolific bloom production, something I’m seeing for myself this year. Prior to this winter, I kept them very sheltered and shaded, so the increased sunlight for winter (I removed my shade cloth) has had a lovely effect on the cacti.
Above is a cold-stressed, water-stressed amerhausi in March 2023, preparing bloom buds.
At right is the same plant, but at the end of summer 2022, showing the difference in stress coloration. Through summer, I kept the plant well-watered, and it stayed on the greener end of the spectrum although still dark.
Growing From Seed
While mine bloom consistently every year, I’ve yet to successfully pollinate them. This isn’t due to any particular difficulty they have, and is purely because with only two, they keep missing each other with simultaneous blooms.
I’m hoping to have seeds later this summer – but no promises!
These are a cactus worth adding to your bench if you like small, easy growers with huge and impressive blooms! Very very enjoyable to keep, and a cactus I highly recommend.