Cactus collectors often end up having a serious problem: we run out of space to keep more specimens. If we are also lovers of columnar species, things get complicated, because although it is true that their roots are not invasive at all and that they do not usually occupy much, to have them in conditions it is necessary to have a site. However, with the Oreocereus trollii we will not have to worry, or not too much.
This species is not only pretty, but it also has a size that makes it a plant suitable for keeping in a pot for its entire life. So, what better than to get to know it? 
How is it?
Our protagonist is an endemic cactus from Argentina and Bolivia whose scientific name is Oreocereus trollii. It was described by Walter Kupper and Curt Backeberg and published in Kaktus-ABC in 1935. It develops a branched stem of up to 60-70cm in height, being the usual 50cm, with a thickness of 6 to 10cm. It has between 15 and 25 ribs, with white areolas covered with wool, which is up to 7cm long.
The spines are yellow, reddish or brown and are up to 5cm long. It also has 10-15 marginal teeth that are like bristles. The flowers are pink to crimson in color, and are 4cm long. The fruits are spherical.
What are their cares?
To have a Oreocereus trollii in good condition just keep in mind that he has to give him the sun throughout the day, and that he has to receive little water. During the summer it will be enough to water it once or twice a week, while the rest of the year we will water it every 15 or 20 days. Likewise, during the warm months it will be necessary to fertilize it with a specific fertilizer for cacti following the indications specified on the package.
For the rest, we can plant it in the ground or in a 3-4cm wider pot in spring, when the risk of frost has passed. And speaking of frost, this magnificent plant resists up to -2ºC without being damaged.