These cacti are attractive, dense little plants that produce large displays of vivid, orange-yellow blooms throughout spring and early summer. I picked one up in late 2021, and have been enamored with the attractive, dense growth since.
Distribution
These are native to Bolivia, in South America, and have a very limited range in their natural environment. They are naturally scarce, and the only reason they are not considered a threatened or endangered species is their remote location and lack of human interest in development in their range.
Plants found in collections are typically grown from seed or division in cultivation, and nearly all are descended from the type locality.
Three type localities/subspecies exist:
- Rebutia arenacea (what I grow & will focus on here)
- Rebutia candiae
- Rebutia glomeriseta
Cultivation
While easy to grow, a few considerations should be made.
Soil
With thick taproots, they can be vulnerable to over-watering and rot, so a well-draining, porous soil is ideal. I prefer a mix of at least 50% pumice for mine, and will be repotting it for the first time in early summer.
You’ll want to watch the part of the plant that narrows to the tap root, the “neck”, and potentially pack in a layer of pumice or rock to ensure rapid drainage and fast drying in the delicate spot. That area is particularly prone to rot, and once rot enters the stem, it’ll ruin your plant.
My plant in January, 2022.
Same cactus in January this year – 2023.
Water and Fertilizer
As you might imagine from the warning about rot, overwatering these cacti is a particular concern.
They should be watered only when dry, and when in doubt, you should simply skip a few days before watering again. During winter months, when the lows are approaching freezing or below, they should be kept entirely dry.
As spring approaches and the weather warms up, you can start watering them again, starting with a small amount on warm days, then a thorough drench as the weather is sunny and truly warm. In my area, we have some warm winter days that I can amplify in my greenhouse, meaning I’ll give mine a splash if it’s warm out.
Encouraging Flowers
Sulcorebutia arenacea require a cold period of rest to encourage good blooming. Temperatures at night should reach 32F, or even a little colder, as long as it doesn’t freeze. These cold temperatures are essential for encouraging blooms, so if you want to see the flowers and grow yours inside – stick it somewhere sheltered outdoors in winter!
I’ve seen the best blooms from mine after a summer growing season with regular fertilizer. I use a 1:1:1 fertilizer at half strength, but not on a rigid schedule. I aim for every time I water at peak summer months, but I’m far less consistent early in the season, or as it tapers off.
Light or Sun Exposure
I have mine in the same area of the greenhouse as my smaller Gymnocalyciums, which I set up with 40% shade cloth in summer, and no protection in winter.
Considerations for my level of shade exposure: my summer months in my greenhouse routinely reach 120F+, and I choose to add shade to try and minimize stress on my plants when it’s super bright. This year, with most cacti accustomed to the greenhouse, I may opt for no shade at all…but we’ll see.
When making any change in light exposure, do so slowly to minimize chances of sunburn. If moving to an area of lower light exposure, watch the cactus carefully for any signs of stretching. The center, apical growth point should remain slightly recessed. There is a good chance the cactus will rot before it etoliates if kept in conditions that are too dark, so keep that in mind. When moving to lower light, hold back on watering, and watch the cactus closely!
I’ll note that a happy, healthy sulcorebutia of this species will change very little in appearance. If you notice significant changes, you’ll need to review your care and consider what might need to change.
Getting a Sulcorebutia aranacea of Your Own
Your best bet to locate one of these cacti is at your local cactus club!
Additionally, sellers may grow them from seed and offer them as young plants on sites such as Etsy or E-bay. Offshoots (such as the one you may see in some of the photos of mine here) are uncommon, but older/larger plants produce them regularly enough to be a viable, if irregular, method of propagation.
I also aim to offer these from seed when possible, so be sure to check my shop for availability!
