Care Diary: Gymnocalycium pflanzii and its varieties

gymnocalycium pflanzii

Written byJen Greene

Animal lover, plant enthusiast, and addicted to the sunshine and warmth in San Diego.

June 24, 2021

I unabashedly love gymnocalyciums.

One of my top five favorite genera, fo. sho.

In large part, it’s because once these reach a certain size, they’re extremely hardy and easy to care for. They thrive in the conditions I have here, notable the high heat and my penchant for watering a tad more than I probably should. 

In this post, I’ll talk about my little collection of Gymnocalycium pflanzii, a species that has numerous varieties or ‘locales’ that are marginally different from each other. 

Basic Care for Gymnocalycium pflanzii

The species originates in Bolivia, Paraguay, and the northern portion of Argentina. Wild plants grow most often in rich, deep soil rather than sparse or rocky soil, and are usually found at least somewhat sheltered under bushes. 

Once established (roughly 2″ or so in diameter), pretty much all varieties follow the same care requirements.

Plants grow to about 6″ in diameter on average, with large specimens being up to 10″ across. Reaches blooming size/maturity at about 4″ tall, although will continue to grow upward with time. Very old gymnocalyciums may be 6 – 10″ tall in cultivation. Our carefully tended, cultivated cacti often reach sizes you would never see in wild specimens, very likely due to the abundance of resources we offer our beloved cacti. 

When raising younger plants, give them plenty of room for roots – a pot with a diameter about an inch larger than the plant itself works, or even slightly bigger so they have room to expand. Plan on repotting your younger plants at least every year until they’re close to mature size, roughly 5″ across.

Soil

While wild plants are found in rich, deep soil, your cultivated specimens should still be potted in a succulent/cactus soil blend. I prefer to mix in at least 25% additional pumice to increase drainage, as I tend to have a heavy hand when watering my gymnos.

And that’s it! You don’t need to find any special additives or mixes. I’d bet these would do just fine in Miracle Gro, if I’m completely honest. They are hardy, easy, and not particularly fussy as long as you meet their next needs.

Heat and Water

I was fortunate recently to attend a talk from Mark Fryer, a well known gymnocalycium expert here in San Diego. He explained something I’d suspected, but didn’t have the sheer numbers or years of experience to be confident in – for happy, robust gymnocalyciums, including pflanzii, you’ll want them to get plenty of heat, and plenty of water.

My Gymnocalycium pflanzii are all out in the elements, with partial shade for the bulk of their day but full exposure to the heat of our inland area. This year, spikes of extremely hot weather started in April, with multiple days at 90+, which occurred through May as well. June’s average high has been at least 80F for all but 2 days, with a heat wave of 90 to just shy of 100F.

I mention these temperatures to give an example of how mine are growing, and thriving, and to contrast against Mr. Fryer’s greenhouse during his talk – which was over 120F and nearly all of his cacti were exploding with blooms!

Whenever I know weather is going to be warm, particularly in the 90F range or higher, I make sure to water the cacti. Gymnocalycium pflanzii tend to show if they are feeling thirsty by blushing dark, even deep purple depending on the cultivar. Albipulpa is a variety that gets notably deep purple with even the hint of stress, while others need more chronic underwatering and heat to develop colors.

When watering, you should ensure the soil is thoroughly drenched and water is running out of the bottom of the pots. You want to ensure that the soil is thoroughly moistened so the cacti have access to plenty of moisture throughout. Ideally, try to time when you water to be in the evening or at least first thing in the morning. Cacti open up their little pores to drink and breathe at night, and yours will appreciate access to water during this time.

Fertilizer

While you can certainly grow these without any fertilizer at all, I feed mine every 2 to 4 weeks during the hottest time of year. This season, I’m using Grow More’s Cactus Juice along with a small amount of Super Thrive and I’m happy with it.

These need a high potassium fertilizer, and Cactus Juice is 1-7-6, meaning by weight the fertilizer is 1% Nitrogen, 7% Phosphorus, and 6% Potassium – a suitably high amount of potassium for these plants. Cactus Juice also has additional calcium, which I appreciate for spine development when fertilizing cacti that don’t necessarily need acidic soil (and thus don’t appreciate limestone or gypsum as a soil additive).

Gymnocalycium pflanzii is not a species that takes calcium and uses it to make spines, at least not as a 1:1 type of growth thing. Instead, for better spination, they need to be grown with very bright light. I find that for my pflanzii, shade during the hottest part of the day and full sun in the morning and evening is enough light for them to have attractive spines and not burn in the sun. 

Gymnocalycium Cultivars / Varieties

I have 4 cultivars of blooming-size gymnocalycium pflanzii, although my assurance that they are the exact cultivars are purchased them as is at about 90%.  I’ll add photos below, and should I find anything definitive about how to identify specific types, I’ll include that as well. I’m experimenting with several types from seed, although only one is unique from the older plants I have. 

Currently Growing: 

  • Gymnocalycium pflanzii, species type 
  • Gymnocalycium pflanzii, var albipulpa 
  • Gymnocalycium pflanzii, var tomina (tominensis)
  • Gymnocalycium pflanzii, var riograndensis
  • Gymnocalycium pflanzii, var lagunillansense (KK850 Lagunillas, Bolivia) – seedlings
gymnocalycium pflanzii albipulpa

One of my larger specimens staged for show in June 2021.

Gymnocalycium pflanzii var. albipulpa

My first variety of pflanzii that wasn’t the ‘species type’. They have a slightly sparkly skin texture, visible even when green and happy, that makes them look almost dusty.

When stressed, this variety gets a deep, dark purple, which you can see below in the plants I first picked up.

Flowers are a pale orange-pink, with neon-pink/red centers.

The deep purple coloration they get when stressed varies throughout the year, most notably during times of stress. They often look their best in winter.

Spines come out red with pale bases, sometimes with striations of yellow and red. 

gymnocalycium pflanzii albipulpa

One of my first albipulpas when I first purchased it in May 2020. The pot is a 6″ diameter pot, to give an idea for size. 

gymnocalycium pflanzii var albipulpa

July, 2020. Heat + water = growth and loss of stress colors. Notice the change in diameter after just a couple months! 

gymnocalycium albipulpa

Same cacti, early June 2021. We’re just entering peak growth season, but before putting much energy into size, they are all blooming like crazy. 

Gymnocalycium pflanzii (species type)

I wish I’d bought more of these when I saw them, as I haven’t seen any quite like it since.

Body is a bright light green, with the same almost-sparkle hue to it that the albipulpa have. Unlike the albipulpa, this never really darkens even when stressed, and the flowers are a distinctly different color. Stress color seems to be to turn a more olive hue, while it remains a brilliant green when kept shaded. 

Blooms are large and have white petals, with a brilliant pink throat that is harder to glimpse than in other varieties. It has some wool around the areoles, but not much, and only around the newest ones. Spines come out bright red with little to no striations. 

gymnocalycium pflanzii

The petals for this flower could almost be a very pale pink, but when seen against other flowers, are more white than anything. 

June 2021.

gymnocalycium pflanzii

Gymnocalycium pflanzii, April 2021. You can see the brilliant green body color and the new spines just starting to grow in as a bright red. If you can, click the photo and check out the body texture – this cactus is hard to beat for a subtle beauty. 

gymnocalycium pflanzii

December 2019 

I hadn’t realized how much this plant had grown until finding the picture from when I first bought it – I haven’t repotted it, so all photos are in the same 6″ pot. 

Gymnocalycium pflanzii riograndense

June 2021

Prolific and repeated blooms. In the 6″ pot I first picked these up in; have not repotted. 

Gymnocalycium pflanzii var. riograndense

The most recent acquisition in this complex, I picked these up in early 2021. Bodies are a shiny green, compared to the slightly sparkly matte of the other varieties. 

Blooms are huge, opening with a slightly pink hue and by the time they are fully open, are a bright white with magenta centers. 

Even new areoles have little to no fuzz, and new spines emerge with distinct striations. Some are more golden and cream, while others are red and cream, but the striations are noticeable. As the spines harden off, they become white as with other varieties.  

gymnocalycium riograndense

Flowers are nearly identical to the “type” pflanzii, but the shine of the body is different. 

June 2021. 

gymnocalycium pflanzii riograndense

Gymnocalycium pflanzii var riograndense when I first brought them home – April 2021. 

gymnocalycium pflanzii riograndensis

Same variety, May 2021, viewed in the shade. 

You can clearly see the spine striations, and the shine of the body.

Gymnocalycium pflanzii var. tomina (tominensis/tominense)

I’ve seen this labeled all three ways above and I have no idea who’s right. Fight amongst yourselves, please. 

Has the matte/sparkle body of others, but much woolier growth at the apical point. Spines don’t seem to follow a pattern – may be initially pale with dark tips, or red, but fade to white. 

Flowers are a cross between albipulpa and pflanzii; start out a peach hue and fade to a brighter white/pink shade as they mature. In my plants, these have the largest flowers compared to the rest. Hard to show accurately in photos, but it’s almost laughable how the large flowers contort themselves among the spines. 

While flowers are peach/pink, similar to albipulpa, these do not seem to stress purple even with low water or cold weather. 

gymnocalycium pflanzii tomina

Gymnocalycium pflanzii var. tomina, June 2021

These are more ‘mature’ flowers, and have a pink hue similar to albipulpa. This time of year, they are very very hard to tell apart, and I’m glad for the pot labels on all of them. 

gymnocalycium pflanzii var tominensis

Gymnocalycium pflanzii var. tomina (tominensis?), April 2021

Does this look almost identical to an albipulpa? 

The main difference seems to be that the albipulpas get a whiff of stress and go full purple – this is the closest to blushing dark I’ve seen these do. Much woolier up top too. 

gymnocalycium pflanzii var tominensis

A different specimen in June 2021. 

You can see the peachy color of the newly opening blooms, as well as an idea of how they get squashed by the spines around them. 

While this cactus has paler spines when new, the flowers behave almost identical to the darker-spined plants, which makes me think they are truly in the same variety rather than offshoots. These have much more individual variety than the others seem to. 

When it comes to blooms and pollination, I’ve noticed that these seem to follow a pattern for pollination. 

The first few days a bloom is open, the stamens produce a ton of pollen, and you can see the bright white or yellow pollen all around the flower edge. The stigma at the center is usually not very open and receptive, but you can still apply some pollen pre-emptively. 

After a few days, the pollen seems to be depleted, and the stigmas really open. 

If you look at the tomina photo above, labeled “different specimen June 2021”, you can see both phases of bloom. On the left is a newly opened flower, with tons of fresh pollen, and on the right is a more mature flower that is ready to receive pollen. The deep pink/red of the inner flower throat seems to attract bees and butterflies, but bees are by far the most enthusiastic pollinators I see visiting these. 

Other varieties I’m growing are seedlings sown this spring, and barely visible even with my jeweler’s loupe, so I will revisit them once they gain some size. 

To follow along as I harvest seeds and sow this year’s crop for the first time, follow me on Instagram! @Trexplants 

You may also like…

Care Diary: Stenocereus beneckei

Care Diary: Stenocereus beneckei

The Stenocereus beneckei is one of those cacti that when you see one grown in greenhouse conditions, or sheltered from...