Islaya krainziana


The name “Islaya krainziana” is actually a synonym of “Islaya islayensis”. Other authors suggest that the real name is actually “Eryosice islayensis”. Another synonym is also “Neoporteria krainziana”.


Islaya krainziana is endemic to an area that extends between northern Chile and Southern Peru. Its habitat is a desert, completely arid, where it never rains: the only water source that can be used by this plant is represented by coastal fogs. It grows partially underneath the soil.


Islaya krainziana is a globose or slightly cylindrical cacti, covered by an intricate net of white spines. The confusion about its name is due to the extreme variability of its appearance. The different forms are however just typical of different populations of the same species. It has a solitary, dark green stem, furrowed by numerous (up to 25), not so pronounced ribs. It stays small, reaching a maximum height of 75 centimeters and 10 centimeters in diameter. An element that stands out a lot about this species is its areoles: they are, literally, white, big buttons, filled in a lot of whitish, thick spines. For those who don’t know, areoles are the typical buds of the family Cactaceae: they are the organs from which the spines are form. On each areole there can be 14 to 25 spines, arranged in 2 to 6-7 central ones, pointing outwards, thick and up to 1,5 centimeters long, and 12 to 18 shorter and less thick ones, pointing in all directions. The colour of the spines varies between reddish-brown to yellow or greyish white. Central spines are usually darker than the radial ones. Flowers appear at the top of ste stem in groups of 3-4. They are yellow, with reddish outer petals and a furry, hairy, elongated calyx. Their blooming season occurs in summer. After withering, they are replaced by characteristic fruits: 5 centimeters long, club-shaped, pinkish-red, fleshy at the beginning and dry when ripen, hosting oval seeds.


Islaya krainziana is not the easiest species to grow and you’ll have to pay attention mainly to root rotting. Here below are our tips:

Place it in a bright spot, exposed to direct sunlight, otherwise it will become stressed and may take on unnatural shapes.
I. krainziana is deemed to tolerated freezing temperatures (down to -5ºC) for short periods of time, if its substrate stays completely dry. By the way, to stay safe, just keep it at temperatures above 5ºC.
Water regularly in Summer, waiting always for the soil to dry up completely before the irrigation. Be careful in the period just after transplants: the plant, at this stage, is more susceptible to root rot. In Winter, keep it completely dry. Suspend any irrigation whenever the temperature falls below 10ºC.
Choose a very well-drained soil, with an abundant mineral part, rich in sand and grit. A standard substrate for cacti will do good, even better if further enriched with sand.
I. krainziana does not like stagnant air. Place it in a airy environment, with a very good ventilation and a dry atmosphere.
Once a year, during the growing season, fertilize a specific product for cacti, rich in phosphorus and potassium and poor in Nitrogen, diluting it at half the dose recommended on the label.
It is a slow-growing plant and, thus, repotting is rarely necessary. Also, the plant becomes more root prone after any repot: we advise to transplant only when it clearly outgrows its pot.


The propagation of Islaya krainziana is mainly carried out by sowing. Sometimes it can be found grafted on more tough cacti such as Selenicereus sp. Seeds should be sown in a fine, sandy, well-drained soil, and be covered in a fine layer of grit. Some suggest to add some fungicide but we don’t agree: maintain the soil moist and keep the pot at a warm temperature. Cover the pot with a plastic sheet to keep them warmer and moist. Germination shold occur in two weeks. While germinating, remove gradually the plastic sheet and don’t disturb the little plants. When they are well-rooted, plant them in separate pots.


Islaya is the name of the Peruvian locality where Backeberg, discoverer of the genus, found the first specimens of this cactus.

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