Care Diary: How to Grow Aloe castilloniae

aloe castilloniae

Written byJen Greene

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

August 2, 2021

Aloe castilloniae is a highly sought after species for true aloe enthusiasts. If you’ve ever looked it up, particularly as a newbie to the hobby, the price tag even on small or young specimens might raise an eyebrow or two. They are a slow growing species from Madagascar, primarily found on porous calcareous sandstone cliffs. 

Their desireability and demand stems from how rare they have been due to being restricted to only a handful of populations in Madagascar. There are multiple forms, with a smooth-leaf form (no tubercules on the top or underside of the leaf) and a textured form being available. The textured form is far more common in part due to tissue culture making them more readily available. 

aloe castilloniae

The various forms of Aloe castilloniae are a result of very limited collections of specimens in the wild, and I have a third type that appears to be between the two extremes – thin, smooth leaves with only a sprinkle of tubercles on top. 

At left, you can see a smooth form castilloniae in the forefront, and a rough form just out of sight in the back. Below is the rough form castilloniae, but in a high-sun exposure, causing the burnt orange sun stress coloration.

aloe castilloniae

Aloe castilloniae was only described in 2006, by Jean-Bernard Castillon, and named in honor of his wife, Bernadette. The newness of the species in horticulture and the limited number of clone types, as well as their somewhat slow growth habit, contributes significantly to their demand. 

Basic Care for Aloe castilloniae

 I do not find any significant differences in care needs between the clones, which is likely due to all of them coming from the same small area with a similar environment. 

Potting & Soil 

This plant prefers to be a bit under-potted, and will be slow to grow branches and leaves if transplanted into something too large right away. Based on my first specimen that I overpotted, then repotted, it seemed to put energy into expanding its root system first before adding appreciable size to the various heads. When left a bit crowded, similar to my smooth form castilloniae, they seem to focus on length and on producing new heads. 

Repot your Aloe castilloniae only when you see roots protuding from the drainage holes, and it’s clear that the plant is root bound. This means needing more frequent water, or the pot feeling light even when the plant has recently been watered thoroughly (a sign the pot is full of roots, not soil). 

The soil should be a blend of quality cactus and succulent soil with 20 – 50% pumice, depending on the humidity and general climate in your region. I potted mine with only about 20% extra pumice, but they do appreciate the extra drainage and air in their root region. Keeping in mind that these aloes grow on porous stone, err on the side of less organic material in the soil than more. 

Fortunately, even if you aren’t at all sure, the aloe will probably be just fine. They are quite hardy and forgiving, particularly the heavily textured clone that is most commonly available. 

Lighting

At right, you can see the same Aloe castilloniae as the red-orange one above, but this is after growing for a month under 50% shade cloth. 

In the wild, these aloes grow in nearly full sun, blushing the reddish color to protect them from the intensity of the sun’s rays. In cultivation, you can see more rapid and robust growth by providing your Aloe castilloniae with some shade, particularly during the hottest part of the day. The shade cloth in my greenhouse is 40%, and my aloes are starting to blush slightly again in response. 

aloe castilloniae
aloe castilloniae sun stress

Above is that same plant, but after 2 weeks of 40% shade rather than 50% shade protection with nearly full sun exposure. 

This means that the plant (and the whole greenhouse) is fully exposed to sun for nearly the entire day, but I use a 40% shade cloth to protect the plants inside. The 40% cloth seems to be about equivalent to 2 – 3 hours of shade, so it’s enough to protect while still allowing for some sun stress coloration. The percentage refers to how much light is filtered, not the percent of the day of sunlight it’s shading, so you’ll have to adapt your shade as needed if you choose to go the shade cloth route. In more northern altitudes, you may not need a shade cloth or shade at all. 

That depends, of course, on the two elements that are deeply intertwined with light:

Temperature and Water 

While they’re adapted to a dry climate, the region of Madagascar they’re from is fairly mild to warm. Even in winter, the lows are rarely below the mid-60s, while average highs are in the mid 80s in summer. 

Despite being adapted to a moderate range of temperatures, these aloes have proven fairly hardy in cultivation. If kept dry in winter, most clones can handle drops down to the low 30s, and in summer, they can tolerate temperatures in the 90s and 100s. A key aspect for any of these extremes is acclimating the plant to them – if you immediately put a greenhouse-grown aloe outside into a frost-prone backyard, it’s likely to rot and fail to thrive. This is true for heat extremes as well! Jumping from a cool greenhouse or nursery to a hot and sunny yard will fry your plant. 

aloe castilloniae smooth form

The hotter the weather, the more water these will accept. You don’t want to overdo it, and they are far more forgiving of being under-watered than over watering. 

A sign that your Aloe castilloniae would appreciate a bit more water is when the leaves begin to curl from the outer edge inward, as in the smooth form on the left. The greater the curl, the thirstier the plant!

Some moderate leaf curl is normal, particularly in hot and dry months, so don’t go overboard if you see it. Just take it as a sign that the plant may like more water and adjust your schedule accordingly – or don’t! Some of the natural variation in growth is normal and can make cultivation of the species more enjoyable.

It can take time for a plant to really plump up after an extended period of low water, and you should try not to flood the poor thing to compensate. Excess water on a regular basis can lead to rotted roots and a dead plant just as surely as not enough water will lead to a crispy plant.

At right is my “intermediate” clone not long after coming home; it was distinctly thirsty but had a poor root system. It’s had to be kept shaded and watered only when dry to ensure it has what it needs to thrive. 

Unfortunately, it crisped from being moved into my greenhouse too quickly, so it’ll take even longer to recover now. 

aloe castilloniae clone

Aloe castilloniae: makes for pretty hybrids

In addition to being a very attractive and striking species, it is popular as a probable ingredient in many aloe hybrids.

These include the Purple People Eater (at least by rumor, I don’t have proof that there’s a castilloniae in the lineage, but they sure look like it), and obviously, the Aloe castilloniae “blue” hybrid. 

aloe castilloniae blue

There’s other species that have tubercules on the leaves, or teeth on the outer edge, but the bright red that’s characteristic of Aloe castilloniae may be a key influence.

Hybrid lineages are often trade secrets, or may not even breed true, and only tissue cultured total clones can resemble a given appearance.

I really can’t say. I’ll leave you with an Aloe “Purple Haze”, which is an example of close, but…not quite like a castilloniae. Could there be a bit in there? Maybe. You’d have to ask the creator, Kelly Griffin, to know for sure!

aloe purple haze

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