The Monvillea spegazzinii cristata, known as “Dinosaur Back Cactus” or “Cristate Monvillea,” is a unique ornamental cactus. Its distinct appeal comes from an unusual growth habit, where its stems develop wavy, brain-like, or fan-like formations. This aesthetic sets it apart from more conventional cacti.
Understanding Monvillea Spegazzinii Cristata
This plant’s crested form, or “cristata,” is a mutation where the growth point flattens and elongates, creating its characteristic wavy or fan-like shape. Stems display blue-green hues, developing reddish or purplish tints with increased sun exposure. Small spines and woolly areoles are present along the crests. Native to arid regions of South America, particularly Argentina and Paraguay, the original Monvillea spegazzinii is a shrubby cactus; the crested form is either a natural or induced mutation.
Essential Care Requirements
Light
Monvillea spegazzinii cristata thrives in bright, indirect light. While it tolerates a few hours of direct morning sun, harsh afternoon sunlight can scorch its delicate crested tissues. Insufficient light leads to etiolation, causing stems to stretch and appear pale. Place the plant near a south-facing window with a sheer curtain, or in an east or west-facing window.
Watering
Water Monvillea spegazzinii cristata using the “soak and dry” method. Allow the soil to dry out completely between waterings to prevent root rot. During the active growing season in spring and summer, water more frequently. Reduce watering significantly during winter dormancy.
Soil and Potting
A well-draining, gritty cactus or succulent mix is essential for Monvillea spegazzinii cristata. Incorporate materials like perlite, pumice, or coarse sand to enhance drainage and aeration, preventing water accumulation. The pot must have adequate drainage holes. Choose a pot not excessively large for the plant’s size; terracotta pots are preferred for their breathability, which helps soil dry efficiently.
Temperature and Humidity
This cactus prefers warm temperatures during its active growing period, ranging from 18 to 32°C (64 to 90°F). During winter, it tolerates cooler temperatures, but protect it from freezing conditions, with a minimum of 10°C (50°F). Monvillea spegazzinii cristata is accustomed to arid environments and thrives in average household humidity, requiring no high humidity.
Fertilizing
Fertilize Monvillea spegazzinii cristata sparingly, only during its growing season (spring through summer). Use a balanced fertilizer or one formulated for cacti and succulents with lower nitrogen. Avoid fertilizing during winter dormancy. Over-fertilization can harm the plant, so follow product instructions carefully.
Addressing Common Challenges
Overwatering is a common cause of rot in Monvillea spegazzinii cristata, manifesting as mushy or discolored stems. Prevent this by ensuring the soil dries completely between waterings and using a highly porous potting mix. If the plant stretches or grows thin and pale, it indicates etiolation from insufficient light. Move the cactus to a brighter location with more indirect sunlight.
Common pests like mealybugs or spider mites can affect the plant. Inspect regularly for infestation and treat with organic solutions like neem oil or insecticidal soap. Occasionally, a crested Monvillea spegazzinii cristata may revert to its non-crested, columnar form, especially if grafted. Prune away any normal growth to encourage the crested form.
Propagation and Display
Propagating crested forms like Monvillea spegazzinii cristata often involves grafting onto a suitable rootstock. Grafting provides stability and promotes faster growth for the delicate crested sections. While propagation by cuttings is possible, the resulting crested form may be less stable or slower to develop than grafted specimens. Allow cuttings to callous for several days before planting to prevent rot and encourage rooting.
The distinct architectural shape of Monvillea spegazzinii cristata makes it an excellent choice for display. Highlight its unique form by planting it in decorative pots that complement its unusual contours. The plant serves as a striking focal point on its own or can be incorporated into succulent arrangements.