Named after William Troll, Oreocereus trollii is also known as the “Old Man of the Andes”. Belonging to the Cactaceae family, this hardy cactus species is native to Bolivia and Argentina and grows in the high altitudes of the arid mountains.
About Oreocereus trollii
The Oreocereus trollii plant has ribbed dark-green colored columnar stems that are covered with wooly white hairs, which look like cotton wool around the reddish-brown-colored spines.
The hairs protect the plant from the extreme sun during the summer months and frost and cold in the winter.
The slow-growing cactus can take up to 20 years to reach a height of around 2 feet. And once it reaches several feet in height, it produces purplish-red or pale pink funnel-shaped flowers in late spring.
A great addition to rockeries and outdoor gardens, in this article, we’ll discuss how to care for the Oreocereus trollii.
8 Types of Oreocereus Cacti [With Pictures]
How to Care for Oreocereus trollii
The Oreocereus trollii grows well when it has bright light all through the day. Full to partial sunlight with good ventilation is best for the growth of the Old Man of the Andes and it does better outdoors than indoors.
If you’re growing the Oreocereus trollii outdoors in your garden, then choose a spot where the plant gets plenty of sunlight.
If you’re growing the plant in a pot or container indoors, then make sure to place the plant in a south-facing window that receives ample sunlight.
The Oreocereus trollii must be watered well in the summer months, during the vegetative period. Make sure to water the plant regularly, but you must allow the surface of the soil to dry up completely before watering it again.
During the autumn and winter months, the plant must be kept dry and it must be just watered to prevent the plant from shriveling. Avoid watering the cactus on days when it is humid, overcast or on cold winter days.
Over-watering the plant or keeping it wet during winter or when the weather is humid can cause it to rot.
The Oreocereus trollii grows best in rich, acidic soil with pH levels between 5.0 to 6.5. The soil must contain around 1/3rd part grit or equal parts of leaf mulch and coarse sand and be well-draining to prevent root rot.
When you consider the feeding requirements, the Oreocereus trollii must be fertilized regularly, once in one to two weeks during summer and spring. You can either use proprietary cactus food or a balanced liquid fertilizer.
Native to the arid mountainous areas, the Oreocereus trollii is predominantly an outdoor plant and does better when planted in outdoor gardens. The cactus does well in warm climates and grows best in USDA hardiness zones 7a to 11b, with temperatures around 20°F.
In colder areas, it is better to grow the plant indoors, as long as it receives plenty of sunlight and is kept dry. It is best not to expose the plant to temperatures less than 20°F, even if the area is protected and well-ventilated.
If you live in an area where the winter months are cold and wet, then it is best to keep the Oreocereus trollii in a sunny greenhouse where the plant is protected and dry from the wet conditions.
In conditions of very high humidity, the plant is particularly sensitive to rot and so you must protect it from excess humidity, especially during the winter months.
In general, the Oreocereus trollii is healthy and is resistant to diseases, but it may be susceptible to pests like mealybugs and red spiders.
The Oreocereus trollii does not require any pruning.
You must re-pot the Oreocereus trollii the first time you bring it from the store. When the roots of the Old Man of the Andes become cramped in the container, then you should re-pot the plant, preferably in spring.
The plant must be repotted once in 1-2 years to provide fresh soil. When you re-pot the Old Man of the Andes, avoid watering the plant for around 1-2 weeks.
How to Propagate Oreocereus trollii
The Oreocereus trollii can be propagated by seeds or cuttings. Since it is a slow-growing plant, it is generally not recommended to grow the Old Man of the Andes by seeds.
You can collect the seeds of the Oreocereus trollii from over-ripe fruits and plant them in March. To propagate the plant using its seeds, the seeds must be planted in well-draining soil and kept at a high temperature and humidity.
You can also propagate the Oreocereus trollii via cuttings. For this method, during spring, make a cut and allow it to dry. The cut surface will dry and form a callus. Place the cutting in a soil, pumice and sand mixture.
You can increase the success of propagation via cuttings by making more than one cutting at the same time.