Echinocactus grusonii is a cactacea native to the arid areas of Mexico; the round shape and the numerous thorns have made this plant to be called mother-in-law's pillow. It is an easy plant to cultivate; it does not need excessive watering, it is advisable to supply water only in the period from March to September; if the plants are kept in the apartment for the whole year let's water them in moderation, if instead we place them outdoors during the summer we water occasionally but with a good amount of water, which will wet all the substratum contained in the vase; In any case let's water with the water only every 7-10 days, when the substratum is completely dry. We try to place the plant in a very well bright place, possibly exposed directly to sunlight, all year long; we avoid drafts and drafts. In nature, these plants can easily withstand even short periods with very cold temperatures, provided they do not receive water during frosts; they can therefore also be grown outside, but only if we can provide a dry place, where the plant does not receive precipitation during the cold season; otherwise we can grow it in the apartment. Every 2-3 years we proceed to repot the grusoni, using a good soil for succulent plants, consisting of a little universal soil, mixed with pumice stone and sand, in order to guarantee an excellent drainage; the new container in which to bury it will be slightly larger than that in which the plant was contained, since these plants seem to prefer poorly capacious containers. Periodically we check that the plant is not attacked by the cochineal, a parasite that lurks in the ground or among the thorns of the cactus, if we notice a few specimens we can remove them using a cotton pad soaked with alcohol, if instead the infestation is of greater entity we will vaporize the plant with mineral oil.