Notocactus oxycostatus f. securituberculatus

It is a solitary cactus, that can become branched over time. It has a dark green stem, that can take on purple shades, if it is exposed to the sun. In summer, a kind of down forms on the apex of its stem. Also the areoles of this cactus change over time: at first, they are white, then turn yellow to finally become bare. The brown spines grow parallel to the stem. It is a plant easy to grow, that blooms in summer with beautiful yellow flowers, which make it perfect for decorating any windowsill.