€10,60

🌱 Morphology
This ornamental plant consists of a scion of Gymnocalycium mihanovichii, typically a mutation colored red, orange, yellow, pink, or even cream, placed via grafting onto a green Hylocereus rootstock. The scion retains the globose shape and characteristic ribs of the Gymnocalycium, while the rootstock features green, triangular stems that grow much faster. The completely colored forms lack sufficient chlorophyll to perform photosynthesis and, therefore, cannot survive on their own roots.

🌍 Origin, history, and taxonomy
Gymnocalycium mihanovichii comes from Paraguay and nearby regions of the South American Chaco. The so-called Moon Cactus is, however, a creation of 20th-century Japanese horticulture. The most documented history attributes to Eiji Watanabe the selection of the first colored mutations: he imported G. mihanovichii var. friedrichii seeds from Germany in 1937 and, after growing thousands of seedlings, selected reddish mutant specimens around 1940. The first individual completely devoid of chlorophyll was reportedly detected in Japan in 1941 and was kept alive through grafting. Commercial forms were introduced later, around 1948, and reached great international popularity starting in the 1960s.

Family Cactaceae · Subfamily Cactoideae · Tribe Cereeae 

❄️ Temperature · USDA Zone 10b
The thermal behavior is largely determined by the tropical Hylocereus rootstock, which is much more sensitive to cold than Gymnocalycium mihanovichii. It is recommended to keep it above 10 ºC and protect it from any frost. Cold, combined with a moist substrate, can quickly cause damage to the rootstock and loss of the graft.

☀️ Lighting
Very bright but filtered light is recommended, avoiding intense sun during the central hours of summer, especially on the rootstock. A PAR radiation of approximately 15–25 mol·m⁻²·day⁻¹ is suitable for maintaining balanced growth and intense coloration without overheating the plant.

💧 Growth cycle and watering
Growth primarily spring–summer. The Hylocereus rootstock needs more heat and humidity than a conventional Gymnocalycium. During active growth, it is recommended to water when the substrate has dried out completely, avoiding keeping it permanently moist. In autumn, watering is reduced, and during winter it is kept very dry, but it should not be subjected to the cold and dry conditions of a Gymnocalycium on its own roots.

🌸 Flowering
The scion can produce the typical flowers of Gymnocalycium mihanovichii, in shades from greenish-yellow to pale olive, although in commercial specimens, flowering is not usually the main ornamental attraction. Under suitable conditions, it can bloom in late spring and during the summer. No sufficiently reliable age of first flowering has been found to establish it as a general data point for this commercial cultivar.

🌿 Why is it grafted?
Here is the key to this plant: grafting is not simply a technique to accelerate growth. In completely colored specimens, it is a physiological necessity. The mutation eliminates or drastically reduces the chlorophyll of the Gymnocalycium, so the scion practically cannot produce its own sugars through photosynthesis. The green Hylocereus rootstock performs photosynthesis and keeps the scion alive through the vascular connection established at the graft union.

🌿 Who started doing it?
The selection and commercial exploitation of these mutants is primarily attributed to the Japanese nurseryman Eiji Watanabe. The first completely achlorophyllous mutant was documented in Japan in 1941 and was preserved by grafting. Watanabe later developed the propagation of these forms, and the ‘Hibotan’ cultivar became the origin of many of the so-called Moon Cacti. However, early history is not documented with absolute unanimity in all sources, so it is more rigorous to speak of Watanabe as the main documented figure of its horticultural development, not necessarily as the inventor of cactus grafting.

🧬 A curiosity
The offsets produced by the colored scion can be separated and regrafted onto new rootstocks. This is how a mutation that could not survive on its own is maintained vegetatively. Grafting, however, has a limited life: Hylocereus grows much faster than Gymnocalycium and, over the years, the union can deteriorate.

🪴 Pot
9x9 cm gourmet black pot

This is an inimitable xerophyte grown in Madrid in a high-tech square pot, with the substrate activated with mycorrhizal fungi and biofungicides.

* As this is an online purchase, the appearance of the specimen sent may vary slightly from the product image. The measurements of the plant are specified in the photo description, but this may also vary slightly because it is a living being! Each of the plants at Desert CITY has unique characteristics.

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