Synonyms:

Cereus spegazzinii f. crestata mostruosa

Habitat:

The crested monstrous form of Monvillea spegazzinii, although originating from a spontaneous mutation, is not stable in the wild and is now preserved and propagated almost exclusively in cultivation. The parent species, Monvillea spegazzinii, is native to the arid regions of northwestern Argentina, where it grows in dry, rocky environments among xerophilous shrubs and the sun-exposed slopes of the Andes. Its natural habitat is characterized by intense sunlight, scarce and irregular rainfall, and poor, mostly sandy or gravelly soils.

Description:

The genus Monvillea is named after Chevalier de Monville, Baron Hippolyte Boissel de Monville (1794–1863), a passionate French botanist and collector credited with several cactus descriptions. The specific epithet spegazzinii honors the Italian-Argentinian naturalist Carlo Luigi Spegazzini, a prominent scholar of South American flora. The designation crestata mostruosa refers to the plant’s ornamental mutation: crestata indicates the fan-shaped growth produced by an abnormal meristematic line, while mostruosa describes the irregularities that give the plant its unusual appearance.

Monvillea spegazzinii f. crestata mostruosa belongs to the genus Monvillea and to the family Cactaceae. It is a rare mutation of the species, distinguished by its crested growth that replaces the typical columnar habit. The stem develops in undulating, sinuous, or fan-shaped formations, with highly variable and irregular shapes typical of fasciated cacti. The epidermis ranges from green to blue-green, depending on sunlight exposure and growing conditions. The ribs appear compressed and reshaped by the abnormal growth, while the areoles are closely spaced and bear generally short, fine spines. The plant grows slowly and tends to widen rather than elongate, forming over time a crested mass with a changeable morphology that varies according to age and cultivation.

Its flowers are remarkably large, measuring 10–13 cm in length, with a slender, elongated tube. The outer tepals are reddish, while the inner ones are white, creating a strong contrast in color. The buds develop near the apex of the stems: initially upright, they bend downward at the moment of opening. This species blooms at night: the flowers open after sunset and remain visible for only a few hours, resulting in a flowering that is both brief and distinctive.

Cultivation:

Monvillea spegazzinii is generally easy to grow and shows a relatively fast growth rate compared to many other cacti.

It requires a very well-draining substrate that dries quickly and does not retain excess moisture. An ideal mix is a mineral-based blend with pumice, lava rock, or fine gravel, with a small amount of light potting soil added if desired.

Watering should be moderate, allowing the substrate to dry out completely before watering again. During the growing season, the plant can be watered regularly, especially if grown in a highly draining mix, while in winter it is best to drastically reduce or suspend watering.

This plant needs very bright light, but direct sun during the hottest hours should be avoided; morning sun, up until midday, is particularly suitable. During the active growing season, it performs best at temperatures between 68 and 86 °F (20–30 °C) and can tolerate slightly lower values if kept dry. It is sensitive to cold and does not tolerate frost: freezing temperatures can cause serious damage, so it is advisable to maintain a minimum of about 50 °F (10 °C) in winter. Humidity should also be kept low to moderate to replicate the arid conditions of its natural habitat.

A balanced cactus fertilizer can be used, diluted to half the recommended strength and applied every four to six weeks during the growing season. Fertilization should be stopped in fall and winter when the plant enters dormancy.

Repotting should be done every two to three years, or whenever roots begin to emerge from the drainage holes. Choose a container only slightly larger than the previous one and refresh the substrate using a well-draining cactus soil mix.

This plant is not considered toxic and can be grown safely indoors. The only caution concerns its spines, which may cause irritation or small scratches; it is therefore advisable to handle the plant carefully, especially during repotting.

It is generally resistant but may occasionally be attacked by mealybugs or mites. Regular inspections and prompt treatment with targeted insecticides or natural remedies help keep these infestations under control.

Thanks to its semi-erect habit and compact size, this plant works well both in outdoor arrangements, where it can be placed in a middle-ground position, and in container culture. It is therefore suitable for greenhouses and collections without being intrusive.

Propagation:

This plant is propagated almost exclusively by cuttings, since seed propagation does not ensure that the crested form will be maintained. Cuttings should be taken from healthy, well-hardened portions of the crest and allowed to dry for a few days until a callus forms. They can then be placed in a very well-draining and slightly moist substrate. Rooting is generally good, especially during the warmer months when the plant is in active growth.

Curiosity:

With prolonged exposure to strong sunlight, this plant can develop an attractive violet coloration, a color shift caused by light stress.

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