Thursday, December 5, 2019

New plant coming to Dave's Botanic Garden - Sulcorebutia rauschii f. violacidermis

As you may or may not know, I've been a succulent plant enthusiast and hobby grower for 25 years.  I live in San Diego, California, which is a great climate for growing many succulent plants.  Anyway, I recently had the idea to acquire several different species of Rebutia cactuses. Rebutia are small easy growing cactuses known for their relatively large blooms and profuse flowering. I had plans to put these plants together in a large pot so I could enjoy their spring flowers each year.

Instead however I took the money I would have spent on several Rebutia and bought one good sized cluster of Suclorebutia rauschii f. violacidermis. It's a very pretty and desirable collector cactus, a version of S. rauschii that has been selected by growers for it's violet skin and propagated to produce more plants for sale. However it's slower and harder to grow than the easy growing Rebutias, which is why it commands a higher price and is thus desirable by professional growers as a profitable plant. I've had an S. rauschii before in the past and managed to kill it pretty quickly.  The plant is known for having thick tap roots that rot easily if over-watered, unlike the filamentous roots of Rebutias.

​Sulcorebutia rauschii f. violaciformis. This is not my plant, just an example pic.  Mine hasn't arrived in the mail yet.

To be more successful growing it this time, I wanted to find out about it's habitat so I could hopefully recreate it's natural conditions here in San Diego.  This is how rare plant growers think, "Under what conditions does this plant live in the wild, and how can I recreate those conditions". So I looked up the plant on and found that it comes from the area around the town of Sucre in Bolivia, in the eastern foothills of the Andes. Then I looked up the elevation of Sucre, over 9000ft, so it lives at some altitude!  The latitude of Sucre is 19 degrees south, technically in the tropics. 

The average maximum temperature in Sucre is only 70°F (21°C).  The highest recorded maximum is only 93°F (34°C). However the average minimum is 45°F (7.2°C) and the lowest recorded minimum is only 24°F (-4.4°C). So it's a cool mountain climate, but not really cold. They get occasional light frosts but no snow.
Rainfall in the rainy season from October to March is 23 inches, wow that's a lot. Most of that rain comes in heavy downpours during thunderstorms. However in the dry season from April to September the rainfall is only 3 inches, very dry.  So it's a typical dry tropical rainfall pattern with big differences in rainfall between the wet and dry seasons.

This explains why many people have trouble growing this plant and why I killed it last time - it can't handle a lot of heat, and it needs to be kept dry in winter. My balcony sometimes gets to 120°F (49°C) in summer, which is much too hot for this plant, and San Diego gets its rainfall at the wrong time of year for it, winter.
So this plant is not one for my baking balcony, it's much too hot there. This plant will be going to "Dave's Botanic Garden Annex", also known as my in-law's house by the coast, where temperatures are more moderate. However, it will need to be shielded from winter rains, to prevent it getting wet during it's dormancy period and rotting.

The shape of the plant also tells me something about it. Unlike Rebutias which live in the cracks and crevices of rocks and have thin filamentous roots to probe for water in those cracks, this plant has thick taproots. This suggests it lives in soil and not in narrow rock crevices.  The big tap roots help store water during the long dry season, and as they dry out and shrink during the dry season they probably pull the plant underground a little, further shielding the plant from the drying effects of sun and wind. 
Sure enough, when I did a Google image search for pictures of Sulcorebutia rasuchii in habitat, it shows the plant growing in soil, and sometimes slightly retracted underground.

S. rauschii growing in soil in habitat and looking plump with water

S. rauschii in in habitat. The plants in the foreground are clearly retracted into the ground.

 S. rauschii partially retracted into the soil.
Note the fine particles of this soil, not well draining at all.

S. rauschii in habitat. Another example of retraction and the soil they grow in.  Flower buds can be seen forming on some of the heads.

I wasn't able to find any good info on the soil these plants naturally grow in. The rocks around Sucre are sedimentary and are derived from the andesite and diorite of the Andes mountains to the west. These kinds of rocks tend to produce clay soils similar to the way granite does, and the habitat photos certainly agree with the soil being a clay soil. However my plant will be planted in my standard succulent soil mix of 1:1:1:1 perlite, red scoria, quartz sand, & potting mix, which I've found to be superior for most types of succulents, and it should do ok with that.

Tadaa!!!  Here's the plant I received after potting it up.  


I'll post some more photos as it grows and flowers.


Here is the same plant on 19 September 2021, 21½ months later.  Now that I re-read my blog, I realize that I've probably been giving it too much sun and heat.  The purple color is on the shady side of the plant, while the sunny side looks pale and perhaps a little burned.  The pot is also in the sun and is black, so probably the roots are getting too hot. I'll move it to a less sunny location and see how it does.

-Dave Bad Person, succulent plant nutcase

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