Melocactus diersianus, also known as the Turk’s Cap cactus, stands out from other succulents with its unique cephalium head and challenging growth requirements. Cultivating this stunning tropical cactus requires an experienced hand, but the effort is well worth it. In this comprehensive guide, we will explore everything you need to know to grow a happy and healthy Turk’s Cap cactus.
Dig in!
Overview
Natural Habitat
In its natural habitat, Melocactus diersianus thrives in the rocky coastal plains and sand dunes near sea level in northeastern Brazil, specifically in Minas Gerais. This cactus has adapted well to survive in its harsh native environment, with poor, dry soil and full sun exposure.
Other Common Names
Melocactus diersianus is also known by Cephalocereus diersianus.
Unique Adaptations
Melocactus diersianus has evolved special adaptations to thrive in its hot and arid homeland:
- Cephalium Head: The woolly, bulbous cephalium provides shade and traps humidity, growing up to 18 cm tall. This will appear as the cactus matures. Mine is still very young, so it hasn’t formed a cephalic head yet.
- Curved Spines: The downward curving spines offer extra shade.
- Shallow Roots: The roots spread out near the surface to absorb moisture effectively.
- Ribbed Stem: The ribbed stem allows the cactus to shrink and swell easily to conserve water.
- Waxy Coating: The cactus has a waxy coating that reduces moisture loss.
Differentiation
Melocactus diersianus stands out from other melocactus species and similar cacti due to its distinctive cephalium head, making it truly unique among its counterparts.
Appearance
Melocactus diersianus is a beautiful and distinct-looking cactus with the following features:
- Size: It grows to a height of 15-30 cm, rarely up to 70 cm.
- Stem: The stem is cylindrical, pale green, with 9-15 acute ribs marked by straight grooves.
- Cephalium: The cephalium measures 10-18 cm tall and 7-12 cm across, adorned with bright red bristles and creamy white wool.
- Flowers: The flowers of Melocactus diersianus are up to 2.7 cm long and 0.9 cm wide, with a vibrant red exterior and deep magenta interior. They bloom in spring/summer.
- Spines: The spines are reddish-brown, grey, and curved downward to provide shade.
Growth Rate
Melocactus diersianus grows at an average rate of 1-2 inches per year. Under ideal conditions, it exhibits relatively fast growth for a cactus, with its peak growth occurring in spring and summer.
Light Needs
Melocactus diersianus requires very bright, direct light, ideally full sun with just slightly less intensity than the most arid cacti. Be cautious, as intense light may cause it to bronze.
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Cold Hardiness
Melocactus diersianus is native to Brazil and cannot tolerate any frost or freezing temperatures. It is sensitive to the cold and goes dormant in the winter, so it’s essential to keep it above 50°F at all times. Ideally, maintain temperatures between 65-80°F and provide winter protection in cooler climates.
How to Care for Melocactus diersianus
Caring for this globular cactus requires some finesse:
Watering
Water Melocactus diersianus thoroughly but infrequently during the growing period from April to October. Allow the soil to dry considerably before watering again. In the winter rest period, water it only once a month, as excessive moisture can lead to root rot. I actually don’t even water my cacti between about November to March unless we get an odd heat wave in San Diego during the winter.
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Rain
Avoid getting the cephalium of Melocactus diersianus wet to prevent rot. Use a covered area outdoors. While the body can tolerate some rain, it’s essential not to overdo it. Once your Melocactus forms a cephalium head, it is more susceptible to rot as the cephalium is wooly and can trap moisture easily.
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Soil
Use a highly porous cactus mix soil with excellent drainage. Repot only when necessary, as the cactus resents frequent repotting.
Fertilizer
During the summer growing months, apply cactus fertilizer at half strength if the plant is actively growing. Avoid feeding it in the fall and winter. Cacti like Melocactus diersianus are accustomed to growing in nutrient poor soils so if you don’t fertilize them at all, they’ll probably be just fine.
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Temperature
Maintain temperatures above 50°F at all times, with an ideal range between 65-80°F, avoiding drastic shifts.
Pests and Diseases
Melocactus diersianus can be susceptible to mealybugs, fungus gnats, scales, and rot. It’s essential to treat infestations early and improve air circulation. Sterilizing the soil can also be beneficial.
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Propagation
Propagate the cactus from seeds in early spring, sowing them in warm, sandy soil.
Pruning
Pruning is generally unnecessary unless the plant is damaged. The cephalium will dry up and fall off naturally, so avoid cutting it off.
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Indoor Growth
Due to its tropical origin, Melocactus diersianus can thrive as a houseplant for experienced growers. To succeed, provide very bright light, suitable temperatures, porous soil, and careful watering. When introducing it to a new environment, acclimate the cactus slowly.
Toxicity
While the cactus itself is not toxic, caution should be exercised around its sharp spines, which can penetrate the skin. I know I’ve been the victim of a cactus spine or two. Leather gloves are a godsend for handling these pretty pricklies.
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Dormancy
During winter, Melocactus diersianus enters dormancy, and its growth slows down. Provide cooler temperatures around 50-60°F and reduce watering frequency during this period. Avoid overwatering until the plant resumes normal growth in spring.
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Etymology
The name “Melocactus” is derived from the Latin term for “melon cactus,” referencing the cactus’s round shape. The specific name “diersianus” honors the German botanist Carl Moritz Diere.
Melocactus diersianus is an exceptionally beautiful tropical cactus that presents some challenges in cultivation. By providing this picky plant with its preferred conditions and expert care, the Turk’s Cap cactus will reward you with its fabulous form and summer flowers. Whether grown indoors or outdoors, its exotic cephalium makes it a striking addition to any space. Prepare yourself for the spikes and enjoy the beauty of this unique cactus.