Synonyms:

Maihueniopsis bonnieae cv. inermis

Habitat:

Puna bonnieae f. inermis is a horticultural form selected from the species Puna bonnieae, which is native to the Andean regions of northwestern Argentina. The species grows in arid, high-altitude environments, on rocky soils poor in organic matter and exposed to intense sunlight.

Description:

Description TextThe genus name Puna refers to the Andean puna, the arid, high-altitude plateau typical of the inner regions of the Andes, which represents the natural environment in which these plants evolved. The specific epithet bonnieae was assigned in honor of Bonnie Brunkow, who discovered the species. The name inermis, from the Latin inermis (“unarmed, without weapons”), alludes to the marked reduction or absence of spines, a feature that distinguishes this form from the type species.

Puna bonnieae f. inermis belongs to the genus Puna and to the family Cactaceae. It is a small cactus characterized by a compact, globular growth habit, rarely exceeding 15 cm (6 inches) in height. The stems are composed of rounded segments, approximately 4–5 cm (1.6–2 inches) in diameter, which over time tend to cluster into dense groups, forming low, ground-hugging cushions. The surface is smooth and green, sometimes developing slight texturing with age. The most distinctive feature of this form is the near total absence of spines: while the type species typically bears 9 to 20 very short, flattened, radial spines slightly curved toward the stem, this form is essentially spineless, with small and inconspicuous areoles.

Flowering occurs in spring and early summer, with solitary flowers appearing at the apex of the segments and displaying a characteristic color change. When first opening, the petals are a light honey yellow, gradually darkening with age. On the second day, shortly before fading, they take on a pinkish, beige-toned coloration. For this reason, yellow and pink flowers can occasionally be observed on the same plant at the same time. Although short-lived, the flowers attract various pollinating insects. The flowers are followed by small, globose, fleshy fruits containing minute seeds.

Cultivation:

Its growth is slow, and cultivation is generally easy.

It requires deep pots and a very well-draining, predominantly mineral substrate. A potting mix composed mainly of inert materials such as coarse sand, gravel, or pumice is recommended, with the possible addition of a small percentage of light potting soil.

During the active growing period, regular watering is required. It is preferable to water deeply but infrequently, ensuring that the substrate has dried out completely between waterings. In spring and summer, watering can be done approximately every 2-3 weeks, while in winter it should be reduced to a minimum or suspended altogether.

It prefers very bright, sunny conditions. Outdoors, it grows well in full sun, receiving at least 6-8 hours of direct light per day. When grown indoors, it should be placed near a well-exposed window. It prefers dry environments with good air circulation and mild temperatures. In colder climates, protection from frost is necessary, and the plant should be kept in a sheltered environment.

The plant does not require frequent fertilization. During the growing season, a single annual application of a low-nitrogen cactus fertilizer is sufficient. Fertilization should be discontinued during the colder months.

Repotting should be carried out only when necessary, approximately every 2-3 years, preferably in early spring. The plant develops a pronounced taproot, making it important to use sufficiently deep pots and a fresh, well-draining substrate.

It is not considered toxic to humans or pets. Although it lacks prominent spines, it may occasionally bear small, barely visible hair-like glochids, so careful handling is still recommended.

It is generally a resilient plant, but it can be sensitive to excess moisture, which may lead to root and fungal rot. Common pests include mealybugs and mites, especially under conditions of poor air circulation or excessive humidity.

Care tip: it is recommended to grow Puna bonnieae f. inermis in deep pots capable of properly accommodating its long, fleshy taproot, avoiding shallow containers that could restrict proper root development.

Propagation:

It is reproduced almost exclusively by vegetative means, through cuttings or grafting, techniques that allow the characteristics of the form to be preserved. Cuttings are obtained by taking a healthy segment, which should be left to callus for a few days before being placed in a well-draining substrate. Rooting is generally possible, but growth on its own roots is slow and the plant may take several years to reach flowering. Grafting is the most common propagation method in cultivation, as it ensures faster and more vigorous development.

Curiosity:

This species develops a fleshy taproot, an adaptation typical of high-altitude cacti, which allows the plant to store water reserves and survive long periods of drought, while also improving anchorage in poor, rocky substrates.

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